Online first articles (not assigned to a volume)
- M. Zheng, T. Chase, J. Yan, S. Jun, V. Sisiopiku, L. Tian, Y. Zheng, X. Wang, B. Schroeder, Z. Qiu, L. ElefteriadouCollection of Transportation Research Procedia (2017).
Abstract
The pedestrian mode is an important component of urban networks, and greatly affects the performance of the sidewalks and crosswalks, as well as the entire network traffic operations by interacting with other traffic modes (automobile, bicycle, transit). There have been many studies concerning different aspects of pedestrian behaviors, such as pedestrian walking speed, pedestrian delay, gap acceptance, signal compliance, route choice, etc. The Highway Capacity Manual (HCM) included the pedestrian mode in the HCM 1994 (update to the HCM 1985) and the HCM, 2010 provided several basic technical methodologies for evaluating the pedestrian level of service (LOS) of different urban street facilities. However, it does not fully cover the pedestrian operation in a great detail and it is missing some important findings in recent studies. The objective of this paper is to provide an overview of pedestrian operations in urban networks, to identify the important aspects of pedestrian operation analysis and to provide recommendations for pedestrian facilities in the HCM on the basis of a summary of available U.S. and international literature. The following topics will be discussed: pedestrian movement models, pedestrian delay estimation, pedestrian-vehicle interactions, and pedestrian travel time estimation. The major features of pedestrian movement along urban segments are the walking speed and available space, which were well examined in past studies. Pedestrian delay is one important measure of pedestrian operation, and its estimation models at signalized/unsignalized intersections are presented with respect to different scenarios. Modifications to the delay model in the HCM, 2010 are highlighted. Pedestrian-vehicle interactions highly affect traffic operations. Both driver and pedestrian behaviors in such an interaction were observed in the field and were examined quantitatively. Pedestrian jaywalking behavior was also observed and its impact on traffic is discussed. Pedestrian route choice at the strategic level and crossing location selection at the operational level jointly determine the pedestrian moving path and further affect the travel time at path-level. A model for estimating pedestrian travel time in an urban network is developed and presented. Such a model can be used to evaluate the facility performance as well as serve for pedestrian route selection. This paper identifies the important aspects of pedestrian operation analysis in an urban network and provides several recommendations to the HCM.Abstract
The pedestrian mode is an important component of urban networks, and greatly affects the performance of the sidewalks and crosswalks, as well as the entire network traffic [...]
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- W. Ackaah, K. BogenbergerCollection of Transportation Research Procedia (2017).
Abstract
The variable speed limit (VSL) system has been implemented on many freeways and urban arterials as a link control strategy. Objectives for deploying VSL systems may include giving advance warning, stabilize and smooth traffic (i.e. harmonization). Accuracy and reliability of the messages displayed by VSL systems can “make or break” its successful implementation. The aim of this paper was to present methods for evaluating VSL systems. As VSL systems may be implemented with different control strategies, an approach for assessing different features of the system independently was adopted. In this way, systems with different control strategies can be evaluated. Methods for assessing incident detection, warning and harmonization abilities were presented. A case study on the VSL system on the Autobahn A99 near Munich, Germany was also discussed.Abstract
The variable speed limit (VSL) system has been implemented on many freeways and urban arterials as a link control strategy. Objectives for deploying VSL systems may include [...]- 0
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- A. Moreno, C. Llorca, A. GarciaCollection of Transportation Research Procedia (2017).
Abstract
The Highway Capacity Manual (HCM) defines the level-of-service criteria for two-lane highways based on three performance measures: average travel speed (ATS), percent time spend following (PTSF) and percent of free-flow speed (PFFS). The performance measures are affected by the lack of passing opportunities, which is quantified through adjustment factors depending on the percentage of no passing zones. Passing zones are provided where available sight distance is greater than the minimum passing sight distance, and their length and frequency depend mainly on the physical constrains and cost limitations. HCM current evaluation of traffic performance excludes horizontal alignment variations, which could produce more or less sinuous alignments and thus affect potentially to both average travel speed and percentage time spent following. Moreover, HCM considers terrain type rather than the actual vertical profile, which could overestimate or underestimate the expected traffic performance depending on how accurately the roadway was adapted to the terrain. The objective of the research is to analyze the relationship between highway horizontal alignment, characterized by curvature change rate (CCR), highway vertical alignment, characterized by the gradient change rate, and traffic performance, based on ATS and PTSF. For the research, 25 Spanish two-lane rural highways were selected. Horizontal geometry was obtained from Google Earth using an azimuth-based restitution program. CCR was calculated and used to identify homogenous segments. Vertical alignment was recreated from GPS data. The sample included 112 homogeneous segments and 451 passing zones. After the geometry-based characterization, 20 homogeneous segments were introduced and simulated in the TWOPAS simulation model. TWOPAS was previously calibrated and validated with passing maneuvers data from Spanish highways. Traffic conditions (directional traffic volume, directional split and percentage of heavy vehicles) were varied. The analysis of the simulation results provided models of PTSF and ATS depending on CCR and gradient change rate, among other parameters. The results of this research will help highway designers and practitioners to predict operational performance based on CCR, type of gradient and expected hourly traffic volume, and could be used as management and design criteria.Abstract
The Highway Capacity Manual (HCM) defines the level-of-service criteria for two-lane highways based on three performance measures: average travel speed (ATS), percent time [...]- 0
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- R. TrappCollection of Transportation Research Procedia (2017).
Abstract
A local non-restrictive ramp metering strategy PRO is introduced. It is based on the stochasticity of capacity. The ramp metering algorithm shows innovative features: • upstream time shifted measurements for anticipation • measurements are actuated every second • up to three vehicles per green are allowed Details of the theory of this strategy are described in the first part. At freeway B27 three ramp meters with the PRO algorithm were installed. In the second part, based on extensive detailed traffic and accident data the effects on traffic flow and safety are described. The impact is positive regarding vehicle speed, queue duration and length as well as capacity and traffic safety. The improvements of speeds, travel times and capacities are statistically significant. The ramp metering systems are highly cost effective.Abstract
A local non-restrictive ramp metering strategy PRO is introduced. It is based on the stochasticity of capacity. The ramp metering algorithm shows innovative features: • [...]- 0
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- T. Bergh, M. Remgård, A. Carlsson, J. Olstam, P. StrömgrenCollection of Transportation Research Procedia (2017).
Abstract
The first Swedish 2+1 median barrier road was opened in 1998. The concept was to retrofit the standard existing two-lane 13 m paved width cross-section at 90 and 110 kph posted speed limit without widening. This design has one continuous lane in each direction, a middle lane changing direction every one to three kilometres with a median barrier separating the two traffic directions. Today over 2 700 km 2+1 median barrier roads are opened for traffic. AADT’s vary from some 3 000 to 20 000 with an average just below 10 000 nowadays normally with 100 kph. The concept has lately been enhanced also to cover the existing 9 m paved width cross-section. The design concept is the same from a driver’s viewpoint, one continuous lane in each direction with a middle lane changing direction and a separating median barrier. This is created by introducing a continuous median barrier and adding overtaking lanes within an overtaking strategy. The differences are the existence of 1+1-sections, less overtaking opportunities and a slightly more narrow cross-section. Some 15 projects are opened. The purpose of this paper is to summarize present knowledge on level-of-service issues as they are presented in Swedish design and assessment guidelines and to give an overview of field measurements and theoretical analytical and simulation studies supporting the recommendations.Abstract
The first Swedish 2+1 median barrier road was opened in 1998. The concept was to retrofit the standard existing two-lane 13 m paved width cross-section at 90 and 110 kph posted [...]- 0
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- T. Wietholt, J. HardingCollection of Transportation Research Procedia (2017).
Abstract
As in many other countries, traffic demand on German motorways is continuously rising, especially during peak hours. Enhancing the road infrastructure by building additional lanes or new motorways is cost-intensive and - due to the complex planning process in Germany – extremely tedious. Thus, the government tries to maximise the performance of the existing infrastructure using dynamic control systems. The development and deployment of autonomous driven vehicles can have positive effects on the capacity of road elements. In this study the effect of dynamic control systems on the traffic flow on motorways is analysed in case studies using microscopic traffic simulation. Furthermore it is outlined that autonomous driving in an environment where access to the motorway is limited to autonomous vehicles only can have a positive effect in terms of higher capacities and more harmonized traffic resulting in fewer traffic breakdowns.Abstract
As in many other countries, traffic demand on German motorways is continuously rising, especially during peak hours. Enhancing the road infrastructure by building additional [...]- 0
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- T. Muramatsu, T. OguchiCollection of Transportation Research Procedia (2017).
Abstract
The function of parking areas at expressway rest stops is to provide drivers with opportunities to park their vehicles for their own purposes, so the number of parking spots has been discussed. However, as the number of parking spots increases, the parking area becomes maze-like and the use of the parking spots becomes inefficient. This leads to skepticism that an increase in parking area capacity will contribute to enhancing parking area performance. Meanwhile, one vehicle is able to park in a parking spot when another vehicle exits the area that is fully occupied, so the condition of drop-by traffic at a rest stop can be discussed using the queuing theory by viewing a rest stop as a warehouse. Thus, this study aims to determine the applicability of the queuing theory when discussing drop-by traffic situations, while assuming a first-in first-out (FIFO) condition. For the applicability of the queuing theory of describing parking area performance, this study employed the ETC probe time-stamp data. The observed values from the ETC probe time-stamp data and FIFO assumed time lags are described, and the applicability of the observed ETC time-stamp data to representing the exact conditions was determined by comparing the number of vehicles parked on the hour every hour and those counted by the observed ETC probe time-stamp data. Finally, the applicability of the FIFO assumption was discussed using the correlation between the observed ETC probe time-stamp data and the FIFO assumed time lags calculated by the data. The results indicate that a FIFO assumption could alternate the observed the ETC probe time-stamp data. The number of vehicles staying on the hour every hour can be represented by the calculation results from FIFO assuming time lags. These findings show that it could be possible to determine the congregative situations of an expressway rest stop analyzed by the ingress and egress time-stamp records. Also, this result assumes any contribution to assessing the functional performance by measuring only the number of vehicles entering and exiting a parking area.Abstract
The function of parking areas at expressway rest stops is to provide drivers with opportunities to park their vehicles for their own purposes, so the number of parking spots [...]- 0
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- P. Strömgren, J. OlstamCollection of Transportation Research Procedia (2017).
Abstract
This paper presents an investigation of capacity reduction in connection with roadwork. The paper presents a state-of-the-art description on roadwork effects on capacity. The state-of-the art has been used to develop a model for estimation of capacity reduction at roadwork zone on Swedish roads. The model has partly been validated with empirical data from a full scale test at the freeway network in Gothenburg. The studies presented in the literature shows that capacity differs not only between different roadwork designs but also between roadwork with similar design. Thus, one can conclude that there is a high variation between the roadwork zone due to effects of surrounding elements, such as the type of work and external effects such as rain (which affects the capacity even under normal conditions). The differences that exist in the estimation of capacity for motorway sections next to a roadwork zone can be said to consist of four situation-specific variables. These four variables are: the percentage of heavy vehicles, type of road, the width of the remaining lanes and diversion of traffic to the opposite carriageway. An increasing proportion of heavy vehicles have a negative impact on roadwork zone capacity. An increasing complexity of work, from light barrier works to extensive bridge repair, has a negative impact on performance. An increased lane width has a positive effect on capacity. The diversion of traffic to the opposite carriageway is often the cause of the bottleneck and therefore has a significance effect on capacity. The conclusion from the literature review is that the most important parameters that should be incorporated in a Swedish capacity manual for the operation and maintenance of roadwork are: the proportion of heavy traffic, lane width, type of roadwork, number of closed lanes, closed road shoulder, proportion of commuter traffic and length of roadwork zone. In general, there have been (too) few empirical studies focusing on the differences in capacity caused by these situation-specific variables. The paper presents a comparison between the Dutch model for computation of capacity reduction and a composite model of reduction factors from Germany, USA and Denmark. The comparison show that the two models essentially gives the same results. Based on these results a new model was developed. In the developed model, the capacity for the remaining lane is calculated. The paper presents results from a field study in Gothenburg where throughput was measured in three cases during a morning hour and one afternoon hour. The capacity was calculated from the normal site conditions according to historical traffic flow and speed data. The result shows that the empirically estimated confidence interval of capacity reduction is consistent with the reduction calculated with the new model for the different cases. The conclusion is that the model can be used to calculate capacity reductions for different roadwork zone configurations but that validation for more configurations is desirable.Abstract
This paper presents an investigation of capacity reduction in connection with roadwork. The paper presents a state-of-the-art description on roadwork effects on capacity. [...]- 0
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- P. Strömgren, G. LindCollection of Transportation Research Procedia (2017).
Abstract
This paper presents an investigation and a state-of-the-art description of traffic effects of harmonization with variable speed limits. Expansion of the E4 south of Stockholm has been carried out during the years 2009-2013. The expansion includes a rearranged lane configuration within the existing road section (25 m) and traffic management systems. Previous design with two lanes and hard shoulder has been replaced with three lanes without shoulder. In addition, the road has been equipped with variable speed limits (with red ring), queue warning system with recommended speed and emergency refuge areas (ERAs). The queue warning functionality was activated in 2011 and harmonization in 2013. Reduced speed variance is an important goal for the traffic management system and is considered to both reduce rear-end collisions and the risk of capacity breakdown. German experience shows that harmonization affects capacity down to about 80 kph. English experience is that the harmonization and monitoring can reduce accidents by 40% at normal speed of 70 mph (112 kph). Germany and England decrease the speed with approximately 20 kph at the degree of saturation of 0.7 to let the flow be harmonized before the traffic density has increased too much. A measure to describe disturbed and undisturbed traffic can be the relative change in the standard deviation of the average speed for 5-minutes periods updated each minute, called CVS. In case of accidents, CVS may be twice as high as normal. The standard deviation of all vehicles is calculated for each minute and aggregated into five-minute periods. The harmonization settings on E4 south of Stockholm has been iteratively designed and ultimately set to 325 vehicles/5 min, which has worked well. The variable speed limit is reduced to 80 kph and stabilizes the flow. The harmonization indicates a potential risk of queue for the road users, which becomes more prepared if the queue warning is activated further along the road due low speed and the risk of sudden braking. The main results can be summarized as follows: • The average speed during rush hour on weekdays has increased by 2.5 kph after the installation of the traffic control system, of which 25% is assumed to be attributable to the traffic management system • The harmonization has delayed the onset of collapse. During the periods in which harmonization has not been activated but there has been a breakdown, it is considered that harmonisation would have passed the half period and then collapse would occurred. • The accidents have been reduced by half, of which 25% is assumed to depend on traffic management (harmonization, queue warning and VMS) The queue warning has worked well, but could be improved by also exploiting the so-called CVS. The measure reveals the instabilities in the flow, sometimes tens of minutes before the AID-alarm due low speeds is enabled. In rush hour when traffic is dense (> 325 vehicles/5 min) and harmonization has already been activated the CVS measure gives further information, which could be exploited to improve the queue warning algorithm.Abstract
This paper presents an investigation and a state-of-the-art description of traffic effects of harmonization with variable speed limits. Expansion of the E4 south of Stockholm [...]- 0
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- S. Axer, B. FriedrichCollection of Transportation Research Procedia (2017).
Abstract
The objective of this paper is to analyze the estimation quality of a staged methodology, that allows the estimation of signal timing information like cycle length, green and red time intervals for time-dependent fixed-time controlled and actuated intersections based on low-frequency and sparse floating car data (FCD). The paper exemplifies, based on simulated dataset, the estimation approach, which assumes as a principle condition the daily repetition of similar signal plans, whereby identical daytime and workday periods are aggregated to reach a sufficient trajectory density. The established concept utilizes efficiently small amounts of FCD trajectories that cover typical sampling intervals between 15-45 seconds. The introduced approach considers three processing stages. Firstly, map matching, data decomposition and stop line estimation are required. Secondly, trajectories’ stop line crossing times are calculated, whereby crossing times of all trajectories are iteratively projected by the application of a modulo operation into the time scale of potential cycle lengths. A statistical data analysis is carried out to estimate cycle lengths and daytime slices with similar signal program patterns. Finally, the last stage of the used approach considers the precise estimation of red and green time intervals based on a histogram analysis. The paper conclusively analyzes the signal program estimation quality considering different degrees of saturation and trajectory sample sizes.Abstract
The objective of this paper is to analyze the estimation quality of a staged methodology, that allows the estimation of signal timing information like cycle length, green [...]- 0
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- S. Hohmann, J. GeistefeldtCollection of Transportation Research Procedia (2017).
Abstract
Achieving the maximum utilization of the existing infrastructure is an essential goal of traffic management for both freeways and the urban road network. Reliable and explicit information about the current traffic condition are required for using the road network efficiently. So far, the lack of a uniform classification scheme results in a time consuming process of coordination between different stakeholders developing and implementing control strategies and providing traffic information. In this study, a uniform concept is developed defining the traffic conditions on freeways and urban roads. This classification scheme is applicable for all stakeholders (e.g. road authorities, broadcasting services, private service providers) and can be used in both infrastructure-based and vehicle-based applications. In order to determine an appropriate traffic flow parameter for a comprehensible representation of the traffic condition, extensive data from freeways and urban roads in Germany were collected and analyzed. The empirical basis is provided by segment-based and local data obtained with different detection methods. As expected, the average speed per segment leads to a more precise description of the traffic condition than local speed values from stationary detectors. Test runs with probe vehicles were made using a GPS tracking device to record the floating cars driving speed. During the test runs, a subjective evaluation of the traffic flow quality was provided by different passengers (probands) in the vehicle. In total, over 15000 sets of travel speed data with associated grading of the experienced traffic flow quality were analyzed to develop a six-step classification scheme. Based on different approaches, threshold values of the average travel speed were determined depending on the type of road and the speed limit. This uniform classification scheme can offer valuable decision guidance for traffic management strategies. For providing more comprehensible traffic information for the road users, the developed scheme was transferred to a three-step system, easily illustrated by the colors green, yellow and red.Abstract
Achieving the maximum utilization of the existing infrastructure is an essential goal of traffic management for both freeways and the urban road network. Reliable and explicit [...]- 0
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- R. Zhou, L. Zhong, N. Zhao, J. Fang, H. Chai, J. Zhou, W. Li, B. LiCollection of Transportation Research Procedia (2017).
Abstract
The achievements of the project “highway capacity research” in the “9th Five-Year” period in China have supported the current “Highway Engineering Technical Standard” and “The Specification of Highway Design”, which are the most important specifications for the design and construction of highway in China and strongly supported the construction and operation of tens of thousands of kilometers of highway. At present, Chinas highway industry is still in a period of rapid development. By the end of 2014, the total mileages of highway network exceeds 4, 400, 000 kilometers, and the freeway’s mileage is 112, 000 kilometers. With this rapid development of highway system, since the “9th Five-Year”, the highway capacity research in China is still ongoing. The report “Development and Practice of China Highway Capacity Research” provides a brief introduction of research history, on-going research and future work of highway capacity research and application in China. Firstly, four main stages of highway capacity research in China are proposed. Stage 1 (before 1990) is called the beginning stage. Stage 2 (1991-2000) is extensive research stage, in which large-scale research is conducted based on the foreign advanced practical experience, such as USA’s. Stage 3 (2001-2010) is in-depth focus on important facilities, and stage 4 (2011 till now) is the adjustment and updating of achievements stage. The report introduces the main representative research projects of each stage and corresponding achievements. Besides, the report also presents the current achievements of China Highway Capacity Manual (CHCM) which is still written. The structure of the manual as well as the new added content such as the capacity analysis of work zone is introduced. The report mainly introduces the achievements of the chapter of basic expressway section in CHCM, which include the new speed – volume relationship of freeway, and the level of service index and classification, and vehicle classification and equivalent coefficients as well as capacity analysis procedure and method. Finally, the report introduces the prospect of future direction of capacity research in China, such as traffic characteristics and capacity dynamic change patterns in huge volume of free pass in holidays etc.Abstract
The achievements of the project “highway capacity research” in the “9th Five-Year” period in China have supported the current “Highway Engineering Technical Standard” [...]- 0
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- R. Troutbeck, D. Walsh, M. BloggCollection of Transportation Research Procedia (2017).
Abstract
Australian States have been investing heavily in managed motorway. It was acknowledged some time ago that the motorways that had slow moving congested traffic caused a considerable loss of value to the community. The concept of Productivity was applied to Motorways and since become a key performance indicator used to rate different motorway systems. The approach to motorway management has been based on established practices overseas although different algorithms are being developed in Australia and subsequently evaluated. This paper describes the processes used by Australian States to manage motorways and it describes the current research into new techniques. The management of motorways cannot be undertaken without consideration of the urban arterial network. It is therefore important to see the network as a whole noting that drivers tend to change their routes so that both the motorways and the arterial work in unison to provide the level of service to the user. It is therefore important that the performance of the arterial road system be maximised. The paper outlines some of the research that is directed at maximising the arterial road, using detectors on the departure side of signalized intersections to evaluating the potential for significant improvement in signal re-timing. Finally the paper will outline the use of the Highway Capacity Manual in Australian traffic engineering practices. It should be understood that Australia has used SIDRA for intersection analysis for some time and although many of the concepts of the HCM are used in SIDRA, it contains many elements and calibration factors that are peculiar to Australia.Abstract
Australian States have been investing heavily in managed motorway. It was acknowledged some time ago that the motorways that had slow moving congested traffic caused a considerable [...]- 0
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- R. Bertini, H. Wang, T. Knudson, K. CarstensCollection of Transportation Research Procedia (2017).
Abstract
Safety remains a problem on U.S. roadways, with more than 32, 000 fatalities, 2.2 million injuries and 6 million crashes each year. Travelers, shippers and the economy are exposed to increasing amounts of congestion, unreliability, delay, emissions and excess energy consumption, which impede the efficient movement of people and goods. The U.S. Department of Transportation (DOT) had embarked upon a major research program toward implementing connected vehicle safety technologies, applications and systems using dedicated, short-range wireless communications (DSRC). Previous research by the National Highway Traffic Safety Administration (NHTSA) demonstrated that 80% of unimpaired driver crash types could be addressed by the connected vehicle technology. Through the year-long Safety Pilot that took place in Michigan from 2012 to 2013, U.S. DOT tested the effectiveness of wireless connected vehicle technology in real-world, multimodal driving conditions, collecting data about how ordinary drivers adapt to the use of connected vehicle technology, and identifying the potential safety benefits of connected vehicle technology. This work was performed in recognition of a February 3, 2014 NHTSA agency decision for light vehicles and a similar decision expected soon for commercial vehicles that will likely launch regulatory processes to require or incentivize all new vehicles to be equipped with DSRC devices. Communication among and between vehicles and the infrastructure (including traffic signals, work zone equipment, or pavement sensors, and other infrastructure elements) would also have data and mobility benefits (including data-driven applications such as traveler information for freight and passengers, transit operations, network flow optimization, traffic signal systems and incident response, emergency staging, and evacuation as well as sustainability-related applications). This paper describes an ongoing effort to explore opportunities for the state of Oregon, USA, to participate in future funded pilot deployments of mobility and environmental related applications in the coming years—possibly including a set of regional pilots as well as smaller, more self-contained projects focused on priority applications. As connected vehicle research moves into deployment, state, local and transit agencies, Metropolitan Planning Organizations and the private sector will start experiencing the effects of vehicles, after-market devices, mobile devices, and infrastructure with DSRC and other wireless connectivity at their cores. Along with other states and regions, the Oregon Department of Transportation (ODOT) can benefit from preliminary scoping, evaluation, and assessment of the impact of connected vehicles and infrastructure and a wide range of potential cooperative system applications. With this in mind, ODOT can determine whether or not to pursue the next phases of federal connected vehicle application funding. It can also make an informed choice about taking a potential national leadership role in the connected vehicle arena, and assess opportunities to join projects with other partners. This paper provides a summary of an internal survey conducted within ODOT along with insights gained from the analysis of the survey results. Next steps in the process are also described.Abstract
Safety remains a problem on U.S. roadways, with more than 32, 000 fatalities, 2.2 million injuries and 6 million crashes each year. Travelers, shippers and the economy are [...]- 0
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- R. Margiotta, D. McLeod, T. ScorsoneCollection of Transportation Research Procedia (2017).
Abstract
The Highway Capacity Manual (HCM) currently uses a bipolar approach to defining level of service (LOS) for freeway facilities: either (1) weighted density or (2) assigning LOS F if one or more segments experience LOS F. The major shortcoming of this approach is that density is a poor indicator of travelers’ experiences under congested conditions, speeds or travel times are more relevant to travelers and are consistent with how agencies measure and report congestion using field data. Likewise, saying a facility operates at LOS F if one only segment experiences LOS F is misleading. Further, five of the six LOS ranges exist where speeds are relatively high (above approximately 50 mph) and only one LOS range is used to define the congested regime, which is of the highest interest in large urbanized areas. Especially with regard to operations improvements, many congestion management techniques will improve congestion (e.g., delay) but the facility will still be classified as LOS F under the current definition. This paper deals with this issue by defining a travel time-based service measure for freeway facilities. Two HCM applications are explored: (1) traditional(static) freeway analysis and (2) the new travel time reliability (TTR) analysis procedure. Several performance measures are explored for the service measures by analyzing field data from seven U.S. urban areas. Although the research is not complete as of this writing, the mean travel time index is probably the best measure for the static procedure and either the 80th or 95th percentile travel time index should be used with the reliability procedure. Analysis of field data revealed strong correlation between the mean and upper percentiles of the travel time distribution, so these measures are internally consistent. A shift away from the current density-based LOS structure is recommended. The new structure uses ranges of the selected travel time measures that indicate different levels of the user experience. This approach is similar to what is done in the HCM for urban streets. Reconciling LOS concepts between freeways and urban streets will make the HCM more usable for the emerging field of performance management. It is recommended that travel time reliability be the service measure for freeway facilities which are part of an extensive freeway network in large urbanized areas, those over 500, 000 population. An extensive freeway network is defined as having at least three freeway facilities. Analysts should use their judgment in cases that do not meet these Density would continue to be used on all other freeway facilities as well as for other aspects of freeways covered by the HCM (e.g., freeway segments). Recognizing that agencies may want to define their own service standards, a procedure for setting locally-defined standards is developed, based on the steps used in this research. It is expected that the freeway facility service measures will be an aid in setting transportation system and freight performance targets, a a demonstration of how they would be used for target setting is presented.Abstract
The Highway Capacity Manual (HCM) currently uses a bipolar approach to defining level of service (LOS) for freeway facilities: either (1) weighted density or (2) assigning [...]- 0
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- R. Dowling, B. Nevers, A. Jia, A. Skabardonis, C. Krause, M. VasudevanCollection of Transportation Research Procedia (2017).
Abstract
This paper reports on the combined microsimulation and small scale demonstration evaluation of the freeway performance effects of a specific connected vehicle implementation of speed harmonization (The Prototype). The microsimulation testing was performed on a 10 mile stretch of freeway in San Mateo County, California. The small scale field demonstration was performed with 10 equipped vehicles on 17 miles of the I-5 freeway in Seattle, Washington. The microsimulation analysis evaluated the effects of the Prototype speed harmonization algorithm on shockwaves, queues, throughput, speed variation, travel time, and reliability, for different response rates for vehicles on the facility. The “response rate” is defined as the combination of the percent of the vehicle fleet with connected vehicle capabilities, the percent of connected vehicles that successfully receive the speed recommendation in a timely manner, and the percent of drivers who having received the recommendation also choose to comply with the recommended speed. Results from the simulation analysis found that the Prototype is likely to significantly reduce the magnitude of the speed differences (shockwaves) between vehicles, even at the 10-percent response rate. This is considered to benefit safety by reducing the probability of collisions where free-flowing traffic meets the back of a queue. The trade-off for the improved safety is that the Prototype increases the geographic impact of existing bottlenecks on freeway speeds by expanding the upstream distance that is affected by congestion. The small scale field demonstration evaluated the performance of a cell phone based application for communicating vehicle status and receiving recommended speeds and advanced queue warnings using a combination of the cellular network and roadside dedicated short range communication devices via a DSRC antenna installed in the vehicle. The small scale demonstration also evaluated the ability to detect queues via a combination of installed loop detectors in the road and basic safety messages transmitted by the connected vehicles. The small scale field demonstration showed the feasibility of connected vehicle data capture and dissemination functionality using both cellular communications and Dedicated Short Range (DSRC) communications. It demonstrated that the Prototype has the communication speeds, communication reliability, and computed processing speed to support speed harmonization application functionality in an operational traffic environment. This paper is based upon work supported by the Federal Highway Administration under contract number DTFH61-12-D-00044. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the Federal Highway Administration.Abstract
This paper reports on the combined microsimulation and small scale demonstration evaluation of the freeway performance effects of a specific connected vehicle implementation [...]- 0
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- R. Avelar, K. Fitzpatrick, K. Dixon, T. LindheimerCollection of Transportation Research Procedia (2017).
Abstract
Freeway networks are a critical component of the transportation systems at large metropolitan areas. The use of managed lanes (MLs) is a very important tool in accommodating directional demand, often heavily asymmetrical at peak hours. Current literature establishes that operational performance of MLs may impact, and be impacted by, operations of adjacent general purpose lanes (GPs), despite some degree of physical separation. Such operational co-dependence may especially exist between the GP lane adjacent to the separation buffer and the ML lane. This paper examines how the operations of these lanes relate to each other. Operational data were collected from 2 freeway sites in Houston TX (U.S.A.) for analysis. Both sites feature a buffer separating a single ML from the GP lanes at each site. One of those sites features vertical pylons in its buffer while the other site does not. This dataset spans several months of year 2014, from January to December. Results highlight the influence of the left-most GP lane on the ML operational speed, as well as the apparent degree of mitigation to that influence that the presence of pylons provides.Abstract
Freeway networks are a critical component of the transportation systems at large metropolitan areas. The use of managed lanes (MLs) is a very important tool in accommodating [...]- 0
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- P. Prevedouros, L. MitropoulosCollection of Transportation Research Procedia (2017).
Abstract
The growth of vehicle sales and use world-wide requires the consumption of significant quantities of energy and materials. Advanced propulsion systems and electric drive vehicles have substantially different characteristics and impacts. For a comprehensive comparison of advanced and traditional light duty vehicles, a model is developed that integrates external costs, including emissions and time losses, with societal and consumer life cycle costs. Life cycle emissions and time losses are converted into costs for seven urban light duty vehicles. The results, which are based on vehicle technology characteristics and transportation impacts on environment, facilitate vehicle comparisons and support policy making in transportation. More sustainable urban transportation can be achieved in the short term by promoting policies that increase vehicle occupancy. In the intermediate term, more sustainable urban transportation can be achieved by increasing the share of hybrid vehicles in traffic. In the long term, more sustainable urban transportation can be achieved with the widespread use of electric vehicles. A sensitivity analysis of life cost results revealed that vehicle costs change significantly for different geographical areas depending on vehicle taxation, and the pricing of gasoline, electric power and pollution. Current practices in carbon and air quality pricing favor oil and coal based technologies. However, increasing the cost of electricity from coal and other fossil fuels would increase the variable cost for electric vehicles, and would favor the variable cost of hybrid vehicles.Abstract
The growth of vehicle sales and use world-wide requires the consumption of significant quantities of energy and materials. Advanced propulsion systems and electric drive vehicles [...]- 0
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- P. Prevedouros, B. HalkiasCollection of Transportation Research Procedia (2017).
Abstract
The forecasting of expressway traffic demand for existing facilities is not particularly challenging for regions and countries with stable or moderately growing economies. In most cases the objective is to carefully establish a reliable estimate for the average annual growth for the next N years using demographic and macroeconomic inputs. Recent applications for freeways and rural highways in Hawaii indicate that the traditional methods using time series or tracking important trends, such as tourism in Hawaii, work well for horizons between 5 and 20 years. Models relying on growth do not adapt well to substantial decreases in traffic demand. A dramatic case is Greece, where a multitude of changes such as increased fuel taxes, reduced GDP, increased unemployment, increased car registration (or car ownership) taxes, and a collapsed new car market caused substantial reductions of traffic on all toll roads in the country, including the Attica Tollway in the capital city of Athens. Given several series of high quality monthly data from January 2005 to December 2012, a number of estimates and forecasts for Attica Tollway toll transactions were estimated. Toll transactions are a measure similar to average daily traffic. ADT represents a traffic load at a specific location whereas toll transactions are the total daily vehicle entries to the facility. Then the 2013 to mid-2015 actual data were used to evaluate the models. Autoregressive models were employed to arrive at toll transaction forecasts between 2013 and 2024. The models used International Monetary Fund (IMF) and Economist Intelligence Unit (EIU) forecasts of the GDP for Greece, as well as scenarios for future fuel prices. The impacts of the much increased fuel prices and of the economic and business downturns to traffic are obvious and the models capture them successfully. However, errors in the GDP forecasts cause errors in the predicted traffic. The stock market index appears to be a useful leading indicator with a two year lag.Abstract
The forecasting of expressway traffic demand for existing facilities is not particularly challenging for regions and countries with stable or moderately growing economies. [...]- 0
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- O. Ramadan, V. SisiopikuCollection of Transportation Research Procedia (2017).
Abstract
Freeway work zones typically mandate lane closures that often induce bottlenecks. Merge maneuvers and the accompanying increase in the rate of lane changes at these bottlenecks can become problematic resulting in undesirable mobility and safety impacts. Traditionally, merge control strategies are deployed to mitigate such impacts. Literature sources indicate that available merge control strategies fall into one of four categories, namely: (i) early merge control, (ii) late merge control, (iii) temporary ramp metering, and (iv) mainline merge metering. However, little is known about the proper criteria for selecting and implementing one of the available merge control strategies. In addition, the impact of the various control strategies on freeway Level of Service (LOS) is currently under-researched. The purpose of this study is to evaluate the operational impacts of the above-mentioned freeway merge control strategies. The goal is to provide work-zone-aware LOS indicators that would help transportation agencies in selecting the most appropriate merge control strategy to minimally impact the freeway operations. In order to meet the research goals and objectives, this study used the CORSIM micro-simulation platform to evaluate impacts of various merge control strategies at a freeway study corridor in Birmingham, AL. The 2010 Highway Capacity Manual methods for calculating LOS were considered and modifications were proposed to align the calculated LOS with the assessed impacts of each merge control strategy. This study is significant for its contribution to providing transportation researchers and professionals with tools and methods to evaluate freeway LOS under work zone conditions and assisting them in mitigating the adverse impacts of work zones on traffic operations.Abstract
Freeway work zones typically mandate lane closures that often induce bottlenecks. Merge maneuvers and the accompanying increase in the rate of lane changes at these bottlenecks [...]- 0
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- N. Wu, S. GiulianiCollection of Transportation Research Procedia (2017).
Abstract
Capacity at signalized intersections is a basic parameter in urban transport networks. The capacity of a signalized intersection is a function of existing geometric, control, weather, and other conditions. Estimation of capacity at signalized intersections is one of the most important topics in traffic Engineering. If the capacity can directly be measured, the delay at signalized intersections and thus the traffic performance and quality of service can be calculated according to the functional relationship between delay and capacity. Unfortunately, under real world traffic conditions, the capacity cannot easily be measured directly for an existing intersection, especially under unsaturated flow conditions where the flow volume is lower than the capacity. This paper presents a model for estimating the capacity of an existing signalized intersection under unsaturated flow condition based on the cycle overflow probability which can be directly measured by loop detectors at stop lines. The cycle overflow probability is just the proportion of cycles with occupied detector at end of green time phases. Also the flow volume can directly be measured by loop detectors at stop lines. According to the queuing theory, the cycle overflow probability is a function of the degree of saturation, i.e. a function of flow volume and capacity. Thus, by measuring the cycle overflow probability and the flow volume, the capacity can be estimated according to the functional relationship. The proposed model is calibrated to data obtained from loop detectors at different signalized intersections under unsaturated conditions. For validation the model, the real capacities at the same intersections are measured for saturated cycles where the capacity can be considers as the measured volume. The proposed model delivers a useful tool for estimating capacity at signalized intersections under unsaturated conditions. Using the proposed model, the capacity and thus the traffic quality of service at existing signalized intersections can directly be estimated using data from loop detectors at stop lines. The model is theoretically reasonable and easily to use for practitioners. The results of the calibration and validation are very promising.Abstract
Capacity at signalized intersections is a basic parameter in urban transport networks. The capacity of a signalized intersection is a function of existing geometric, control, [...]- 0
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- N. Wu, K. LemkeCollection of Transportation Research Procedia (2017).
Abstract
The first version of German Highway Capacity Manual was published in 2001. Now, a new version is published in 2015 (HBS 2015). For the new German Highway Capacity Manual, most major chapters are revised and some of them are totally rewritten. The chapter for merge, diverge, and small weaving segments is rewritten in accordance with forthcoming developments in the past 10 years. In this paper, an overview of the chapter in the new German Highway Capacity Manual is presented. Procedures dealing with performance analyses and level of service (LOS) of those segments are introduced both for freeways and rural highways. Differences between the former version and the new version of the chapter in the German Highway Capacity Manual are indicated and discussed. In most of the existing highway capacity manuals, LOS of merge, diverge, and small weaving segments is traditionally defined by speed, volume, or density in critical areas. In that traditional concept several capacity values of different critical areas (merge, diverge, and weaving) as well as upstream and downstream basic segments within the influence areas are evaluated separately. In the new HBS 2015, a new model which considers the total merge, diverge, and weaving segment as an entire object is incorporated. A combined volume-to-capacity ratio (freeways) or a combined density (rural highways) is used for defining the LOS of the total segment. The parameters of the new procedure are functions of the number of lanes of the major road, the number of lanes in the on-ramp or off-ramp, and the predefined geometric design of those segments. The coefficients are calibrated with field data or defined by experts’ experiences within a matrix of coefficients. With those procedures, the traffic quality (LOS) can be obtained directly as a function of the volumes or densities on the major road and on the on-ramp or off-ramp respectively. The new procedure has the following advantages: a) a uniform function for all types of merge, diverge, and small weaving segments, b) traffic quality assessment for all critical areas under investigation in one step, and c) the procedure can easily be calibrated. For applications in practice, a set of graphs is provided.Abstract
The first version of German Highway Capacity Manual was published in 2001. Now, a new version is published in 2015 (HBS 2015). For the new German Highway Capacity Manual, [...]- 0
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- H. NguyenCollection of Transportation Research Procedia (2017).
Abstract
This article describes the results of a comprehensive saturation flow rate analysis at signalized intersections in motorcycle dependent cities. Most of current capacity analysis methods for signalized intersections consider vehicles moving on lanes, and they assume lane discipline and high driver discipline regarding traffic regulations. Moreover, for modeling mixed traffic conditions, the not lane-based heterogeneous real traffic flow is transferred into lane-based homogeneous flow by using Passenger Car Units. So far, available methods of capacity analysis do not consider the specific conditions of driver behaviour and traffic flow which are dominant e.g. in Vietnam or other countries where motorcycles have the major share in traffic. Consequently, there is a need to develop a proper method to allow such saturation flow rate analysis. The methodology of this research was developed with consideration of the specific traffic situation in Hochiminh City, Vietnam, a motorcycle dependent city. First, the article describes the unique aspects of traffic flow and saturation flow rate analysis under such mixed traffic conditions compared with car-dominated traffic, using data collected by observations of saturated flow conditions at 12 signalized intersections. Then, saturation flow rate models using a regression method are presented and described. The term of Motorcycle Unit (MCU) is introduced, and a set of factors which mainly affect the saturation flow in such mixed conditions is developed. These factors reflect major differences between the traffic flows under saturated conditions at signalized intersections in motorcycle dependent cities and car-dominated cites. For example, this includes the influence of the approach width, the impact of four-wheel vehicles (including car, bus, and truck) on motorcycles, the very specific interactions of left-turning and opposite straight-moving traffic streams, the relationship between right-turning 4-wheel vehicles and motorcycles moving straight in the same direction, and the phenomenon of capacity drop within the green time. Finally, a procedure to calculate the saturation flow rate for specific traffic situations is provided, and the application of the proposed model is depicted. The conducted research indicates that the proposed saturation flow rate analysis model is an appropriate approach to calculate the saturation flow rate for traffic streams at signalized intersections under such mixed traffic conditions. The set of motorcycle equivalent units used for analysis is also proved to be suitable for this model. Equations and graphs to determine the appropriate values for the identified influencing factors are presented. According to each specific traffic situation, calculation procedures are provided to determine the value of the saturation flow rate.Abstract
This article describes the results of a comprehensive saturation flow rate analysis at signalized intersections in motorcycle dependent cities. Most of current capacity analysis [...]- 0
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- N. Singh, P. Parida, M. Advani, R. GujarCollection of Transportation Research Procedia (2017).
Abstract
The most important parameter for designing a pedestrian facility is the area required by a pedestrian to stand comfortably or make a comfortable movement. This area is referred as Body Ellipse (Human Ellipse) and depends on Shoulder Width and Body Depth of a human being (and also on the kind of activity i.e. Standing or Walking). In current practices, design of pedestrian facilities’ are according to the body ellipse of pedestrians experimented in The United States Of America (US-HCM 2010). Regional variances are marked in these physical characteristics that are dependent on human body dimensions to a greater extent, ultimately playing an important role in pedestrian’s convenience (capacity and Level of service of a facility) and design environment. This paper is an attempt to study the measurements of Body Ellipses i.e. body depth and shoulder width by carrying out videography surveys on the pedestrians in India (specifically Delhi). The analysis also includes, classifying the body dimensions according to gender and walking with/without baggage (handbag/backpack), along with the measurement of the Step length of pedestrians’ while walking which shall give out the area required for walking. These body dimensions have been compared with the standard body dimension available worldwide. The study location was a walkway in a commercial area in Delhi (India) with a sample size of 747 consisting of 132 females and 615 males. The extracted body dimension varies from 26.07 to 52.14 centimeter for body depth and 42.35 to 67.76 centimeters for shoulder width.Abstract
The most important parameter for designing a pedestrian facility is the area required by a pedestrian to stand comfortably or make a comfortable movement. This area is referred [...]- 0
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- N. Motamedidehkordi, M. Margreiter, T. BenzCollection of Transportation Research Procedia (2017).
Abstract
The rapid development of wireless communication and information technologies has increased research interests in inter-vehicle communication systems and their effect on traffic flow. One of the most complex traffic phenomena on freeways are shockwaves. Shockwaves are recognized as the sudden, substantial change in the state of the traffic flow, which acts as an active or moving bottleneck. They have significant impact on freeway capacity and safety. For this study, a microscopic traffic simulation was used to determine the extent to which inter-vehicle communication and change in the driving strategy after the recognition of a shockwave can influence the propagation and dissolving of shockwaves on freeways. We also briefly introduce the shockwave theory and our communication algorithm. Then we present the simulation result with different penetration rates of communicative vehicles, which are randomly dispersed in traffic flow, through performance measures for traffic flow with shockwaves.Abstract
The rapid development of wireless communication and information technologies has increased research interests in inter-vehicle communication systems and their effect on traffic [...]- 0
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- N. Kang, H. NakamuraCollection of Transportation Research Procedia (2017).
Abstract
Heavy vehicles behave differently from ordinary passenger cars due to their characteristics such as size and operational performance. At roundabout, entry capacity estimation mainly focuses on passenger cars. In HCM 2010, the impact of heavy vehicles on entry capacity is considered through a heavy vehicle adjustment factor fHV which includes heavy vehicle percentage and passenger car equivalent (PCE hereafter) value. It is generally set as 2.0, which means a heavy vehicle is assumed to be equivalent to two passenger cars. In existing methods, the PCE value at roundabouts is estimated based on several considerations such as entry capacity and move-up time. All of these considerations are influenced by local driver behavior and geometry conditions. Thus, this paper aims to estimate entry capacity considering the characteristics of heavy vehicle behavior in Japan. In this paper, characteristics of heavy vehicle behavior such as speed and gap parameters are firstly analyzed by using data observed at several roundabouts in Japan. Then, a simulation study which is calibrated based on the observation data is conducted by applying VISSIM 5.40. Roundabout entry capacity is estimated through assuming different heavy vehicle percentage values of each entry. Based on the estimated results of entry capacity, PCE value is calculated. The PCE values from the simulation study are compared with those values adopted by several design guidelines. Through the empirical analysis, it is found that heavy vehicles move in lower speed than passenger cars in the process of travelling roundabouts. The headways which are formed by heavy vehicles are commonly greater than those only formed by passenger cars. Then, PCE values which are calculated from simulation output are shown to change with different combinations of heavy vehicle percentage of each entry. The results in this paper provide a reference for roundabout entry capacity estimation considering heavy vehicle behavior in Japan. Future works are some further analysis from the viewpoint of geometry, since heavy vehicle behavior is significantly influenced by roundabout geometry such as inscribed circle diameter and circulatory roadway width, particularly at compact roundabout which is often the case in Japan.Abstract
Heavy vehicles behave differently from ordinary passenger cars due to their characteristics such as size and operational performance. At roundabout, entry capacity estimation [...]- 0
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- M. Hartmann, P. VortischCollection of Transportation Research Procedia (2017).
Abstract
Unlike the U.S. 2010 Highway Capacity Manual, the most recent edition of German Highway Capacity Manual does not include methodology to evaluate the facility within oversaturated time periods. To incorporate this traffic flow regime within the methodology, we identify several aspects of the methodology that require enhancements and propose modifications. Next, we implement these modifications in a macroscopic traffic model developed as a software implementation of the German guideline. In this manner, the HBS user can conduct traffic flow analysis that includes volume-to-capacity ratios above 1.00 which has not been foreseen by the guideline until now. The main contribution of this paper is the identification of methods within the German Highway Capacity Manual that require modification to enable incorporation of oversaturated traffic flow within the analysis. Further, we introduce traffic density as a variable within the HBS methodology and show benefits of its incorporation during the oversaturated time periods. Finally, the paper includes illustrative examples of empirical and model-based evaluation of congested freeway facility in Germany. The paper concludes with a discussion of proposed methods and their limitations.Abstract
Unlike the U.S. 2010 Highway Capacity Manual, the most recent edition of German Highway Capacity Manual does not include methodology to evaluate the facility within oversaturated [...]- 0
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- M. Martin-Gasulla, A. Garcia, A. Moreno, C. LlorcaCollection of Transportation Research Procedia (2017).
Abstract
Roundabouts show great advantages due to their geometry and their priority system, both in terms of capacity and road safety, compared to other intersections. However, unbalanced flows may be a problem even at medium demand levels. One single approach may cause queues on the downstream approaches as drivers are not allowed to entry the roundabout. If that downstream approach has the highest flow demand, average delay is highly increased, so, the roundabout can be collapsed. This operational problem is derived from one of roundabouts fundamental properties: movements with greater traffic demand cannot be prioritized, unlike signalized intersections. A few solutions may be found, but the most cost-effective measure is traffic regulation by metering signals. The aim of the research is to analyze capacity improvements and operational performance on roundabouts with metering signals using traffic microsimulation, for Spain local conditions. Metering signals are based on creating gaps in the circulating stream in order to alleviate excessive delays on the main approach of the roundabout. Consequently, they are used only on heavy demand conditions during peak hours. On the metered approach, which causes problems for a main downstream approach (controlling approach), metering signals are implemented. The metered approach is stopped by red signals controlled by a queue detector on the controlling approach. So, the controlling approach is benefited by metering signals as drivers can easily enter the roundabout, and the roundabout overall traffic operation is improved. The research was conducted in 5 stages: roundabouts selection, field study, calibration and validation of a traffic microsimulation model in VISSIM, generation of multiple scenarios, and, analysis of the results. Two roundabouts with known unbalanced flow patterns on Valencia (Spain) were selected, traffic counts were carried out to describe their traffic flow patterns, which resulted on limited capacity at both locations. In order to quantify traffic operation improvement on metered roundabouts, a traffic microsimulation model in VISSIM was elaborated. The model was calibrated and validated using critical gaps, queues, delays, and speeds. Afterwards, a metering signal technique was implemented on VisVAP, based on an ad hoc signal control logic design. Almost 400 combinations of design and control metering signals parameters were required to obtain the optimal model (distances to yield line, red and green time settings) which presented the lowest average delay. It could be concluded that, for the same medium-high circulating flow, a higher demand would be able to enter the roundabout (of up to 80% from the controlled approach) with less average delay values (22% and 56% at each studied roundabout) by installing metering signals.Abstract
Roundabouts show great advantages due to their geometry and their priority system, both in terms of capacity and road safety, compared to other intersections. However, unbalanced [...]- 0
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- M. MargreiterCollection of Transportation Research Procedia (2017).
Abstract
This work describes an approach to determine the current travel times on freeways based on the detection and re-identification of Bluetooth devices onboard of vehicles using stationary roadside Bluetooth detection technology. It also aims at using this information for the traffic state determination of a whole freeway network with the goal of a fast and reliable dynamic net control in incident situations. Based on a four year experience in a Bluetooth detector test bed in Northern Bavaria, Germany, and after the evaluation of hundreds of millions of single detections, the technology as well as the developed algorithms for validation and evaluation of the data show their feasibility in practical use, especially in areas with a low density of stationary detectors like inductive loops. The data-driven part of the approach is divided into three subsequent steps. These steps are the determination of travel times, the data filtering and validation of plausible travel times and the automatic incident detection. The determination of travel time is based on the time stamp of the detection of a Bluetooth device with the shortest estimated distance to the position of the Bluetooth detector. For the data filtering the “Time Dependent Comparison to Neighbor Values Filter” will be applied. This filter allows for a fast and reliable differentiation between unrealistic (due to stops, detours, back and return trips etc.) and plausible travel time values for a certain segment of the freeway and is based on a method to validate if the determined travel time is in a plausibility threshold corridor defined by the values of the previous and the next neighboring travel times. The outcome is a detailed travel time information for the whole freeway network which is used for an automatic incident detection, which was developed and calibrated within this research project. This includes the detection of the start of an incident as well as the end of an incident. The result is continuous information about the prevailing travel times and a fast and reliable traffic state information for all segments, which allows for a dynamic large-scale re-routing in the Bavarian freeway network in case of congestions or other disturbances of the traffic flow.Abstract
This work describes an approach to determine the current travel times on freeways based on the detection and re-identification of Bluetooth devices onboard of vehicles using [...]- 0
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- M. MailerCollection of Transportation Research Procedia (2017).
Abstract
The paper is based on a project carried out to develop a new concept for the assessment of highway performance considering multi-modality, traffic management and ITS. Step by step a single-mode concept like it is used in the Austrian guidelines is extended to a multi-modal transport approach taking into account the capacity and quality of different modes on the road as well as in the corridor. By showing different options of meeting the quality target of road traffic this concept is aiming at a more efficient and cost effective use of traffic infrastructure and supporting the efficient allocation of limited funds. In order to allow for multi-modal considerations, transport demand has to be measured in persons and goods rather than in vehicle units. For the assessment of roads this combines the utilization of traffic capacity in terms of vehicles with the utilization of vehicle capacity in terms of occupancy and loading. So a multi-modal approach has to consider the characteristics and potentials of public transport on the road and of alternative means of transport in the corridor. The corridor comprises the road that has to be assessed as well as all parallel means of transport. The whole transport demand in passengers and goods using this corridor is taken into account. Corridor capacity results from the capacity of all means of transport. However, since the concept still focuses on the assessment of highway performance the transport contribution of the other means of transport is considered as reduction of the transport demand and hence of traffic load on the road. To finally assess the level of service on the road different criteria can be used. So the implications of using travel speed or reliability of travel time which is related to capacity utilization are discussed. Especially in hilly or mountainous regions a speed based assessment can result in problems due to unreasonable alignment and expensive road construction. Therefore the influences of different design parameters, horizontal alignment and grade as well as the traffic mix (proportions of heavy vehicles) on speed and capacity are analyzed in detail. The extended concept of road assessment is allowing multi-modal capacity utilization and capacity management to meet quality targets of road traffic. It supports the identification of different scenarios how transport demand can be accommodated adequately. It extends the range of suitable measures to respond to unsatisfactory quality of road traffic. Apart from road improvements it allows for management measures controlling a given demand rather than just accommodating it.Abstract
The paper is based on a project carried out to develop a new concept for the assessment of highway performance considering multi-modality, traffic management and ITS. Step [...]- 0
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- L. Shi, P. PrevedourosCollection of Transportation Research Procedia (2017).
Abstract
Major IT companies and vehicle manufacturers have announced their plans for autonomous driving technology. Autonomous light duty vehicles are often referred to as “driverless cars” (DLC). These technologies intend to partly or fully replace driving by combining navigation systems, artificial intelligence, in-vehicle sensors, roadside ITS and traffic monitoring data, vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. The absence of perception errors and the minimal perception and reaction time of DLC enable them to maintain shorter headways, to apply consistent acceleration and deceleration rates, and to optimize the use of gaps. In theory, freeway operations and level of service (LOS) can be impacted to a substantial but yet unknown degree by the DLC. The Highway Capacity Manual (HCM).is a static and macroscopic methodology for assessing various traffic flow facilities. Its 2010 edition is not adjusted for the presence of DLC on highways, however, several of its parameters are sensitive to differences in perception and reaction times, headways, etc. An investigation was conducted to assess the likely changes to traffic flow characteristics that may result from the introduction of DLC. The focus of this paper is on expressways, that is, on HCM analyses of basic freeway segment and freeway weaving segment. DLC is able to increase capacity (c), the maximum service flow rate (MSFi), the adjustment factor for unfamiliar driver population (fP), passenger-car equivalent (PCE), and the proportion of heavy vehicles (PT). The combined benefits improve LOS. The results from the case studies show that the impacts of DLC on HCM parameters are tiny if the DLC have a very small market share. Two types of DLC are considered in this paper: Autonomous DLC, and Connected DLC with V2V and V2I. On a basic freeway segment the Autonomous DLC improves LOS from D to C when its share in traffic reaches 7%. The same case study shows that the Connected DLC improves LOS from D to C when its share in traffic reaches 3%.Abstract
Major IT companies and vehicle manufacturers have announced their plans for autonomous driving technology. Autonomous light duty vehicles are often referred to as “driverless [...]- 0
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- K. Suzuki, K. Imada, Y. MatsumuraCollection of Transportation Research Procedia (2017).
Abstract
For usability of urban expressway in Japan, there are some problems due to the limitation of spatial con-straint. As the result of the limitation, there are merging sections that do not have enough length and set a right-side entrance ramp which is connected to the passing lane, directly. Therefore, unfamiliar drivers such as female and/or elderly drivers are subjected to stress and aware of danger when they merge onto the expressway and it is necessary to measure these situations quantitatively from the viewpoints of both traffic conflict risk and users evaluation. The purpose of this study is to estimate collision risk by using Surrogate Safety Measure and evaluate Quality of Service for drivers at merging sections of urban expressway in Japan. We focused on each ve-hicle merging movements and traffic conflicts at three on-ramps, which has different geometries, by im-age processing technology. First, in order to elucidate the occurrences of collision risk in merging section, we analyzed the collision risk between a merging vehicle and a main lane vehicle by using the Possibility Index for Collision with Urgent Deceleration (PICUD) index. It is shown that the position of conflicts is affected by the amount of traffic volume. Second, we conducted discriminant analyses for the results of the PICUD estimation in order to reveal the influence factors of collision risk at each merging section. As the result of discriminant analyses, it is found that the percentage of merging position and traffic volume of main lane have a huge effect on collision risk for merging movement. In addition, both the percentage of heavy vehicles and the existence of other merging vehicle at a time trigger rear-end collision risk. Fur-thermore, we examined some countermeasures to reduce collision risk in objective merging sections by sensitivity analysis and proposed a Level of Service index which is based on the rank of rear-end collision risk considering users’ subjective evaluation.Abstract
For usability of urban expressway in Japan, there are some problems due to the limitation of spatial con-straint. As the result of the limitation, there are merging sections [...]- 0
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- K. Bang, J. Wahlstedt, L. LinseCollection of Transportation Research Procedia (2017).
Abstract
A detailed procedure for capacity analysis of signalized intersections was first produced in 1976 and presented at the TRB Annual meeting (Bang, Hansson, Peterson 1978). In the eighties computer aids (named CAPCAL) based on this methodology were developed including traffic as well as safety and emission performance measures for different types of at-grade intersections. Capcal has been continuously updated since then, the last version CAPCAL 4.1 was based on a major Swedish HCM project called METKAP 2009 – 2013. The theoretical basis for the calculation procedures as well as the software are still subject to revisions based on user inputs. National base parameters and other variables are also included in these updates. CAPCAL 4 also adds improved capabilities to visualize calculation results. The use of CAPCAL is mandatory in projects for the Swedish National Road Authority, and it is also commonly used by local authorities, consultants and universities in Sweden. The computational methodology for signalized intersections is based on an iterative process including the following functions for each calculation cycle:Determination of saturation flow for all types of unopposed or opposed discharge. Traffic flow distribution between lanes in the same sub-approach.Identification of the critical conflict point for traffic streams that are served by different main signal phases (Min∑_1^n▒q/s).Signal timing for minimum total delay or other object function.Determination of traffic performance at normal and oversaturated conditions Special consideration has been devoted to development of the following sub modules: Automatic calculation of inter-green times and minimum green periods which give instant feedback of geometry changes Short lane utilization and contribution to approach bottleneck capacity. Procedure for identification of the critical conflict point for complex intersection configurations and phase schemes including extra or alternative phases for efficient discharge of turning movements.Optimal signal timing including considerations to minimum green and lost time restraints Consideration of exit capacity Calculation of delay and other traffic performance variables for forcasted traffic flows including improved handling of oversaturation Linking of capacity model to existing modules for calculating impact on environment, costs and traffic safety. The method is limited to isolated intersections, and based on fixed timed signals. Impacts of Traffic Actuated signal control is approximated by signal timing corrections (max green, green time extension intervals) based on traffic simulation results for different types of control strategies. In further work those corrections will be enhanced and also include the impacts of bus priority in vehicle actuated signal control using a more complex probability based model.Abstract
A detailed procedure for capacity analysis of signalized intersections was first produced in 1976 and presented at the TRB Annual meeting (Bang, Hansson, Peterson 1978). In [...]- 0
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- J. Xing, J. TanakaCollection of Transportation Research Procedia (2017).
Abstract
1. Introduction & Objectives Traffic congestion has been an important social issue in all over the world. It will result in great economic loss due to time delay and environment deterioration. In Japan, traffic congestion on intercity expressways on weekends and holidays is not an unusual scene. Looking at the percentage of congestion occurring on Japanese intercity motorways by bottleneck type, nearly 80% occurs in uninterrupted flow sections of sags or uphill slopes (60%) and tunnel entrances (20%). Congestion at merge areas accounts for approximately 13%. At a high level of traffic flow before occurrence of congestion, there exists a difference of travel speed between outer lane and inner lane, eventually causing an increase in use of the inner lane. The resultant inequality of lane utilization results in a breakdown of traffic flow in the inner lane of multilane motorway while flow of the outer lane remains below its capacity, thus decreasing the directional capacity. Once congestion occurs at a bottleneck, capacity would drop from pre-queue breakdown flow rate to lower queue discharge flow rate during congestion. As a measure against congestion, queue discharge flow from a bottleneck could be increased by providing drivers with information on the location of the head of the queue using roadside VMS. It is also possible to correct the overuse of the median lane by adding an auxiliary lane around the bottleneck at a sag. Besides, correction of unbalanced lane use could also be achieved by the provision of traveller information, such as “Please keep left” or “Please use left hand lane” to drivers through the VMS before occurrence of the congestion, (care should be taken here that vehicles drive on the left in Japan). However, there is no guideline on effective addition of an auxiliary lane in sag section for mitigation of motorway traffic congestion. This paper uses a microscopic traffic simulation model to study the effective way of adding an auxiliary lane in sag section of a dual 2-lane motorway for mitigation of traffic congestion. 2. Results The study considers 2 types of auxiliary lanes in sag section, i.e. one diverging and merging from outside, and one diverging from inside and merging from outside. The length of auxiliary lane varies every 500m from 500m to 2, 000m. The auxiliary lane is added at various locations ending at or starting from the bottom of a sag, or starting from the start of a vertical curve, or starting from around the midpoint of upstream half of a vertical curve. Altogether 15 cases are considered for the simulation study. The microscopic traffic simulation model is used in the study. Prior to the simulation runs, some parameters are calibrated to check if the 5-min average speed and median lane utilization agree with the observed data. The spatial distribution of lane utilization before, inside and after an auxiliary lane is also examined. The output of the simulation runs in the study is breakdown flow rate for each case of auxiliary lane. It is seen from the simulation results that for an auxiliary lane diverging and merging from outside, the optimum length should be 1, 000m – 1, 500m and be added from around the start of vertical curve to several hundred meters beyond the end of vertical curve. This is in accordance with the observation that shock waves take place in the length of auxiliary lane of a sag section. The auxiliary lane longer than the optimum length does not seem to result in higher breakdown flow rate. With the same length of auxiliary lane, the one diverging from inside and merging from outside would yield higher breakdown flow rate than the one diverging and merging from outside from the viewpoint of increasing the breakdown flow rate.Abstract
1. Introduction & Objectives Traffic congestion has been an important social issue in all over the world. It will result in great economic loss due to time delay and environment [...]- 0
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- J. Dierke, J. Kleine, R. LehmannCollection of Transportation Research Procedia (2017).
Abstract
The high density of commercial freight transport on motorways makes it difficult for truck drivers to find safe parking places especially for longer rest periods during the night. Even though expansions have been made to satisfy the demand in Germany, overcrowding and dangerous situations still occur as a result of vehicles parking on the entrance and exit roads of rest areas. In 2005 a control procedure called “Convoy Parking” was installed at the rest area Montabaur on the A3 motorway in Germany. Convoy Parking is subject to a patent (EP 1 408 455 B1, 2007). Convoy Parking requires all drivers entering their departure time at a terminal in front of a barrier. Subsequently, on the basis of the input data, the automatically detected vehicle length and the actual situation at the rest area, a free parking row is assigned and trucks can be parked sorted. The German Federal Highway Research Institute (BASt) developed a new control procedure called “Intelligent Controlled Compact Parking” (hereafter referred to as “Compact Parking” for short) to achieve that trucks are parking in a compact way, side by side and without a driving lane between trucks. Convoy Parking and Compact Parking have a very different control procedure and appearance. While Convoy Parking assigns a parking row to the driver, Compact Parking deliberately leaves the choice of the parking row to the drivers themselves. Drivers do not have to disclose their departure time to any system and they are not stopped by any barrier because Compact Parking offers a wide range of departure times on variable message signs. Drivers ought to use the parking row where their intended departure time is offered. With the innovative system Compact Parking the capacity of an existing rest area can be quickly increased without enlarging the area. This also avoids long-term planning approval procedures and is friendly to the environment. Besides, the safety for all users of the rest area can be improved by reducing illegal parking. Compact Parking is supported by the German Federal Ministry of Transport and Digital Infrastructure (BMVI). The first installation of Compact Parking is under construction at the rest area Jura-West on the A3 motorway (Northern Bavaria). The Autobahndirektion Nordbayern (Motorway Directorate for Northern Bavaria) is the central agency to plan, build and run the motorways in Northern Bavaria and got the approval of the BMVI to realize the pilot project. BASt accompanies the pilot project and leads the implementation of the control procedure. The opening is scheduled for summer 2015.Abstract
The high density of commercial freight transport on motorways makes it difficult for truck drivers to find safe parking places especially for longer rest periods during the [...]- 0
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- J. Chodur, K. Ostrowski, M. TraczCollection of Transportation Research Procedia (2017).
Abstract
Urban and rural intersections differ in terms of functionality. They support traffic which differs in terms of travel goals and motivations. In urban areas, these goals are mainly related to work, home, shopping and recreation. On the other hand, rural intersection mainly support through traffic between towns and cities and regions, with a small admixture of local traffic. Comparison of the characteristics of traffic flows indicates that towns and cities have heavier traffic flows, mainly of light vehicles, and frequent congestion states, while rural areas reveal smaller traffic flow and its structure is more diverse and involves vehicles travelling at higher speeds. The structure of traffic directions at rural intersections, usually dominated by traffic moving along one of the intersecting roads, differs substantially from the structure of the same at urban intersections. In order to control traffic, rural intersections increasingly rely on varied in time traffic signals, with a preference strategy whenever there is absence of excitation of motion detectors by the participants. The scope of intersections expansion and traffic control algorithms are more varied at urban intersections. Rural intersections are mainly controlled based on three major driving phases. Differences in intersections locations and the specificity of traffic conditions and traffic control imply drivers’ different needs and behaviour. Hence it is important to conduct comparative analyses of urban and rural intersections. The paper will present analysis of variability of saturation flows and capacity and traffic performance based on empirical studies of intersections in 2008 – 2012, both in urban and rural areas. Differences in drivers’ needs and behaviour in rural areas, the specific distribution of types of vehicles and directions on the lanes (single carriageway and dual carriageway) translate into slower vehicle service processes. Smaller values of saturation flow and capacity in rural areas mean that significant periodic increases in traffic flow lead to congestion states much faster than in urban areas. Although in rural areas these states are rather rare for the main direction, they are much more common at entries to the main road. The seasonal variability of traffic makes the functioning of these intersections differ between business (non-recreational) and recreational traffic (e.g. during the holiday season). The paper will also address the issue of acceptance of difficult traffic conditions in the states of traffic overload from the point of view of the road managers and the driver, referring to the reliability of intersection entries in urban and rural areas.Abstract
Urban and rural intersections differ in terms of functionality. They support traffic which differs in terms of travel goals and motivations. In urban areas, these goals are [...]- 0
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- J. So, S. Hoffmann, J. Lee, F. Busch, K. ChoiCollection of Transportation Research Procedia (2017).
Abstract
This study proposes advanced safety assessment methods in the perspectives of prediction performance and practicality. This study thus develops three different safety assessment approaches (simulated conflicts-incorporated, estimated conflicts-incorporated, and intersection operational attributes-based safety performance function) and utilizes two existing approaches (annual average daily traffic-based and simulated conflicts-based safety performance functions. These five safety assessment approaches are compared in terms of crash prediction performance at intersections and practicality representing the required efforts in implementing a method. The results showed that the simulated conflicts-incorporated safety performance function approach was best in terms of prediction performance while the annual average daily traffic-based safety performance function approach was best in the practicality aspect. The discussion on trade-off between prediction performance and practicality then followed based on the analysis on the prediction performance and practicality aspects. This study will be a reference to safety assessment practitioners when they need to assess safety on roadways and to select an appropriate safety assessment method with limited resources.Abstract
This study proposes advanced safety assessment methods in the perspectives of prediction performance and practicality. This study thus develops three different safety assessment [...]- 0
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- H. Kita, H. Yotsutsuji, R. Asaka, J. Tsujitani, T. WatanabeCollection of Transportation Research Procedia (2017).
Abstract
Developing driver-oriented highway performance measures is the key to performance-based highway design. Highways should be designed so that an appropriate performance measure corresponding to major highway functions can achieve a required level of quality of traffic service. Quantitative assessments of performance measures need to evaluate the achieved level of performance as compared with the required level. Various measures have been proposed, such as overall travel speed, target travel speed, travel time, traffic safety, traffic density, congestion, freedom to maneuver, and driving comfort and convenience (HRB, 1965, TRB, 1985, FGSV, 1988). However, it is unclear how existing performance measures relate to driver perceptions of the quality of traffic service. This study focuses on ease of access to destinations as a new driver-oriented performance measure under various driving conditions on interurban expressways connecting hub cities. This measure indicates the ease of maintaining vehicle speed near a target travel speed while maintaining a constant headway in the lane. We hereinafter refer to this measure as “interurban accessibility.” Interurban accessibility can be expressed as the sum total of utility that each driver perceives from smooth and safe traffic flow at each point in interurban expressway lanes. The objectives of this study are twofold. One objective is to develop an estimation method for interurban accessibility based on driver utility as proposed by Kita et al. (2014) . Their experimental results indicate that our proposed measure more appropriately describes driver perceptions of the quality of traffic service than do previously proposed performance measures. The other objective is to demonstrate how to use interurban accessibility to determine the planning level of the performance measure in comparison with a required level of quality of traffic service. In modeling the interurban accessibility measure, the level of interurban accessibility decreases as travel time between hub cities increases or as freedom to maneuver decreases because of congestion and delays. Hence, our model of interurban accessibility assumes a target travel time, defined as the travel distance divided by the target travel speed, so interurban accessibility is presumed to increase with travel speed. In addition, Kita and Kouchi (2011) showed that perception structures of interurban accessibility are momentarily formed by accumulating perceived values. Hence, our model involves both average and minimum point-based utilities in microscopic driving environments, so that accident risks contingent on speed can be considered for each point-based utility. Moreover, accumulation of point-based utilities between hub cities is considered to exert a decisive influence on the level of interurban accessibility. Driver memory is assumed to decay over elapsed driving time. Hence, accumulated point-based utilities are multiplied by a time discount factor, so that average point-based utilities are obtained to average the discounted point-based utilities. This study proposes a method for assessing the planning level of performance measures by means of an interurban accessibility estimation model, as compared with a required level of quality of traffic service. We therefore utilize exceedance probability of a probability distribution function regarding interurban accessibility. Note that, regarding traffic management and control through the use of a highway performance measure, it is believed to be better to apply data from roadside continuous-traffic-monitoring devices. Therefore, this study proposes a method for assessing interurban accessibility by examining traffic volume, which is easy to observe at each device. Before assessing the planning level of the measure as compared with the required level, the distribution of the interurban accessibility measure must be particularized. We presents a flowchart for specifying the distribution of a measure. The procedure of this flowchart requires a probability distribution of instant utility and a probability distribution of difference in instant utility between two points. The former requires distributions of time headway and spot speed, and the latter requires microscopic driving environments such as space headway that each driver perceives. Both the former and the latter require data on traffic volume and travel distance. The travel distance here means a given highway distance between hub cities. The distributions of the time headway and spot speed are affected by traffic characteristics such as road gradient and large-vehicle mix rate, in addition to the traffic volume. The following describes the procedure of the proposed flowchart. Firstly, assuming that the distribution of the time headway and that of the spot speed can be approximated by a log-normal distribution and a normal distribution, respectively, data on both the time headway and the spot speed are generated. Secondly, assuming that the distribution of the instant utility and that of the difference in instant utility between two neighboring points can be approximated by a shifted log-normal distribution and a Cauchy distribution, respectively, data on both the instant utility and the difference in instant utility between two points are generated. Thirdly, according to the point-based utility model, the number of point-based utilities for each point is generated based on Monte Carlo simulation employing both the distribution of the instant utility and that of the difference in instant utility between two points. Finally, a distribution of the interurban accessibility can be obtained from the interurban accessibility estimation model. Here, as a critical value indicating an exceedance probability of 85% in this distribution, a planning level of the performance measure is considered. Through a numerical example, we confirmed that the proposed measure can better describe driver perception than can existing measures such as travel speed. Consequently, we believe that performance-based highway design considering data obtained from vehicle detectors is possible by considering interurban accessibility as the performance measure.Abstract
Developing driver-oriented highway performance measures is the key to performance-based highway design. Highways should be designed so that an appropriate performance measure [...]- 0
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- H. Heikoop, N. HenkensCollection of Transportation Research Procedia (2017).
Abstract
Around 1995 the need for a Dutch Highway Capacity Manual (HCM) was felt within Rijkswaterstaat (Rijkswaterstaat is the executive body of the Dutch Ministry of Infrastructure and the Environment). Previously the American HCM was used, but specific circumstances in the Netherlands made it necessary to develop a Dutch HCM. This led to the introduction of the Dutch HCM, Handboek Capaciteitswaarden Infrastructuur Autosnelwegen in 1999, followed by the 2nd edition in 2002. Then, after a long period a completely new 3rd edition was published in 2011 and a fourth edition was completed in 2015. More than 15 years of research on highway capacities and the experience in using the manual has resulted in a practical handbook with an obligation to use it in planning studies for new and renewed highways in the Netherlands. The manual is one of the guidelines implemented in a working process system for planning studies. Although different indicators have been used over the years in transportation policy, the volume-to-capacity ratio is still the main indicator for the traffic flow quality in the Dutch HCM. Before the introduction of the Dutch HCM (< 1999) this indicator had been used most frequently. The most recent fourth version of Dutch HCM includes the research of capacities of tapers, cloverleaves, rush hour lanes and 4 lanes freeways. Weaving sections received special attention, as they are still simulated with the microsimulation model FOSIM. The new information was mostly added after requests of users. Because of a bigger role of consultants and less involvements of experts of Rijkswaterstaat in the highway designing process, guidelines become much more obligatory and nowadays contain specific minimum values and other specifications of the highway elements. Analysis has also been performed of capacity measurements at more than 200 locations. The influence of, among others, lane width, speed limit, absence of emergency lanes, tunnels and bridges have been analyzed. Also different road work configurations have been analyzed. The results from these analyses have been used in the fourth version of the Dutch HCM to state the influence of different infrastructure elements on the capacity and to validate and update previously stated values.Abstract
Around 1995 the need for a Dutch Highway Capacity Manual (HCM) was felt within Rijkswaterstaat (Rijkswaterstaat is the executive body of the Dutch Ministry of Infrastructure [...]- 0
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- H. Waleczek, J. Geistefeldt, D. Cindric-Middendorf, G. RiegelhuthCollection of Transportation Research Procedia (2017).
Abstract
Work zones on freeways usually affect the quality of service for road users. Aiming to reduce traffic flow disruptions to a minimum, Hessen Mobil – Road and Traffic Management installed an innovative reversible lane system in a work zone on Autobahn A 3 south-east of Frankfurt, Germany. The section with three lanes and temporary hard shoulder running in both directions carries a high amount of commuter traffic with considerable fluctuations in peak traffic flow direction. During road works, four lanes in the peak direction and three lanes in the non-peak direction could be maintained through the use of a reversible lane system. The paper discusses the effects of the reversible lane system on traffic flow and road safety. Radar measurements revealed a maximum traffic volume of roughly 1500 veh/h on the reversible lane, which is around 25% of the total traffic volume during peak hours. The capacity of the work zone was estimated with the stochastic capacity estimation technique based on models for censored data. Compared with the capacity of the unaffected three-lane carriageway with temporary hard shoulder running, a decrease of the capacity by 14% to 17% was estimated for the four-lane work zone configuration including the reversible lane, depending on the direction. The difference between the capacities in both directions can be explained by the different lane geometries at the respective beginning of the work zone, leading to a higher number of lane changing manoeuvers directly upstream of the lane diverge in one direction. The traffic flow analysis also yielded a considerable impact of the work zone on peak hour traffic demand volumes, which were reduced by approximately 1000 veh/h. Similar to other freeway work zones, the road safety analysis revealed an increase of accident rates during road works. However, based on police accident reports only 10% of the total number of accidents and none of the severe accidents could be linked to particular features of the reversible lane system. Altogether, the investigation shows that a reversible lane system is a useful, safe and accepted instrument of intelligent traffic management for freeway work zones with high fluctuations in peak traffic flow direction. At the analyzed work zone, estimated travel time losses of 400000 veh*h could be saved during two months of road works by the application of the reversible lane compared with a permanent lane reduction in one direction.Abstract
Work zones on freeways usually affect the quality of service for road users. Aiming to reduce traffic flow disruptions to a minimum, Hessen Mobil – Road and Traffic Management [...]- 0
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- P. Greibe, T. BuchCollection of Transportation Research Procedia (2017).
Abstract
The main objective of this study is to examine how widths of cycle tracks influence the behaviour, flow and capacity of bicycle traffic. Empirical data has been collected by video observations at 8 different cycle tracks of varying widths (1.85m-2.85m excl. kerb between cycle track and carriageway). The locations are characterised by high bicycle traffic volumes on the track, no traffic lights / junctions / bus stops / zebra crossing nearby, and no dividing verge between cycle track and carriageway. Speed and lateral positions has been measured for 8, 925 cyclists. The average speed is 21.6km/h but differs slightly between locations. Women ride 2-3km/h slower than men but also with a smaller dispersion. The traffic volume does not affect average speed, but dispersion decrease with increasing bicycle traffic volumes. At narrow cycle tracks cyclists are riding closer to the footpath and closer to each other during overtaking compared to cycle tracks of a larger width. Car parking in the road side next to the cycle track reduces “the effective width” of cycle track with about 10-15cm. High bicycle traffic volumes are only observed in short time spans and it seems like the capacity limit is not reached. Flows as high as 20 bicycles per 10 sec are observed at a 2-lane cycle track (width: 2.35m) and still with an average speed of about 21km/h. Controlling factors are used when calculating capacity from short time spans, and the hourly capacity of a 2-lane cycle track has been estimated to about 3, 000bicycles/h. The width does not affect the capacity much unless the number of lanes are reduced or increased. A cargo bike has an average speed of 16.3km/h and its headway is 1.3 times as big as the headway of a traditional bicycle. Due to the speed and the size of a cargo bike it reduces capacity equally to 3-4 traditional bicycles. Based on the data minimum and recommended widths of bicycle tracks are found.Abstract
The main objective of this study is to examine how widths of cycle tracks influence the behaviour, flow and capacity of bicycle traffic. Empirical data has been collected [...]- 0
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- G. Schultz, S. Mineer, C. HamblinCollection of Transportation Research Procedia (2017).
Abstract
This paper reports on an analysis conducted to identify ways to improve average speeds in the Express Lanes (ELs) in Utah. The research began with an investigation of the current usage of both the ELs and the General Purpose (GP) lanes by user type (e.g., single-occupant vehicle, high-occupancy vehicle (HOV) 2, HOV 3+, “C” decal, Express Pass user, motorcycle, bus, freight vehicle, and emergency vehicle) to better understand the breakdown of vehicles in the lanes and to calculate average vehicle occupancy. Violation data were examined to determine ways to reduce violator rates, while ways to control Express Pass traffic and to evaluate changes to toll rates and to estimate the impacts on speed of specific toll increases along the corridor were explored. The data collected were examined to better understand the speed-flow relationship on the ELs and to estimate the impact of volume changes on speeds in the lanes. This allowed the research team to estimate the impact on EL and GP lane volumes and speeds under a combination of EL education campaigns, increased EL enforcement, and increased EL peak period toll rates. Depending on the scenario analyzed, it was determined that the speeds in the ELs could be expected to increase as a result of the recommendations. The increase was found to be dependent upon the scenario chosen and the response of the traffic to the increases with an average maximum change in EL speed of 7.8 mph for a combination of education, enforcement, and increased tolls.Abstract
This paper reports on an analysis conducted to identify ways to improve average speeds in the Express Lanes (ELs) in Utah. The research began with an investigation of the [...]- 0
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- J. GeistefeldtCollection of Transportation Research Procedia (2017).
Abstract
The second edition of the German Highway Capacity Manual HBS was published in 2015. The paper presents the HBS procedure for the assessment of basic freeway segments and discusses challenges for the future development of the methodology. As in the former edition of the HBS, the volume-to-capacity ratio is used as measure of effectiveness for basic freeway segments. The design capacities and speed-flow diagrams for basic freeway segments were completely revised and supplemented by new design values for segments with four-lane carriageways and segments with hard shoulder running. Besides the provision of specific design capacities, the reduced capacity variance on segments with variable speed limits, which was ascertained in recent investigations, is considered by adjusting the lower threshold value of LOS E. The new edition of the HBS also provides a framework for the use of specific parameters and the application of alternative methods for the assessment of traffic flow quality. Overall, the revised procedure for the analysis of basic freeway segments includes major enhancements and covers a larger number of segment types, but the main concept still follows the tradition of using deterministic capacities and providing rather simple analytical procedures to assess the traffic flow in one specific peak hour. For the future development of the HBS, the application of computer-based simulation models as well as the use of stochastic traffic flow parameters that better represent traffic reliability will increasingly emerge.Abstract
The second edition of the German Highway Capacity Manual HBS was published in 2015. The paper presents the HBS procedure for the assessment of basic freeway segments and discusses [...]- 0
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- G. Riggins, R. Bertini, W. Ackaah, M. MargreiterCollection of Transportation Research Procedia (2017).
Abstract
Variable Speed Limit (VSL) and Variable Advisory Speed (VAS) systems are applications of a growing field of active traffic management systems (ATM). This technology aims to improve safety while reducing congestion and emissions. VSL is common on German freeways, harmonizing traffic flow during congestion and weather events. Portland, Oregon installed a VAS system (advisory meaning it is not automatically enforced) on an eleven km (7 mile) segment of heavily congested urban freeway. The Portland region maintains archived, high-resolution data of both VAS sign messages and speed detection loop feedback, permitting reconstruction of traffic and sign data. This work analyses over 30 days of archived data from the Portland site in order to study driver compliance to the VAS signs. The focus is to suggest methods and parameters to score system performance. Such an analysis could benefit new rollouts of VAS corridors by providing system performance feedback and shed light on options for improving system performance.Abstract
Variable Speed Limit (VSL) and Variable Advisory Speed (VAS) systems are applications of a growing field of active traffic management systems (ATM). This technology aims to [...]- 0
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- M. FriedrichCollection of Transportation Research Procedia (2017).
Abstract
The German Highway Capacity Manual HBS (Handbuch fuer die Bemessung von Strassenverkehrsanlagen, FGSV 2015) like other Highway Capacity Manuals provides a collection of methods for evaluating the Level of Service for single road facilities, i.e. a particular network element like a road segment, a ramp, or an intersection. The Level of Service of single road facilities (LOS) is derived from the volume capacity ratio, the delay time or the traffic density. In addition to the HBS the German guidelines provide a complementary Guideline for Integrated Network Planning RIN (Richtlinien für die integrierte Netzgestaltung, FGSV 2008) which is used for categorising transport networks and for evaluating the service quality in multi-modal networks. Here the LOS refers to entire journeys, i.e. to origin-destination-pairs. The most important indicator for evaluating the service quality of a particular od-pair is the direct speed (= direct distance / journey time). Journey time and the resulting direct speed include not only the in-vehicle time but also access and egress times which can reduce the speed of the entire journey significantly, especially in public transport. Additional indictors evaluation the directness and the travel time ratio of competing modes complement the set of indicators for evaluating the service quality. For each indicator the guideline provides evaluations functions for the service levels A to F which depend on the direct distance between origin and destination. This reflects the fact that speeds typically increase with longer distances while detour factor and travel time ratio decreases. The paper summarizes the approach of the guideline for evaluating the service quality and presents experience with the evaluation scheme collected in various applications covering car and public transport networks. It shows how the evaluation results can be used to recognize shortcomings in the network not only on the level of od-pairs but also to identify critical network elements. Finally the paper explains how the two guidelines HBS and RIN are connected.Abstract
The German Highway Capacity Manual HBS (Handbuch fuer die Bemessung von Strassenverkehrsanlagen, FGSV 2015) like other Highway Capacity Manuals provides a collection of methods [...]- 0
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- F. Rempe, G. Huber, K. BogenbergerCollection of Transportation Research Procedia (2017).
Abstract
Traffic congestion in urban areas is a big issue for cities around the world. Thus, studying congestion and respective counter measures is of high importance for the increasing urbanization of society. Congestion analysis and forecast is most of the times done either on a link-wise network or on a network-wide level. Though, due to bottlenecks in the infrastructure and similar commuting patterns by road users, usually the same parts of an urban traffic network get congested. The idea is to observe and investigate primarily these most vulnerable parts of the network, which are denoted as congestion clusters, as they are crucial to both, drivers and operators. A methodology for determining congestion clusters is described, which provides a significant amount of flexibility to be able to meet different needs for different applications or cities. Based on a five months set of Floating Car (FC) data, the suggested methodology is tested. First analyses are conducted to understand up to which degree these clusters are able to represent the congestion level of the entire network. Besides, correlations between the clusters are investigated on a statistical basis and conclusions are drawn. The results provide a basis for potential traffic estimation and forecast systems.Abstract
Traffic congestion in urban areas is a big issue for cities around the world. Thus, studying congestion and respective counter measures is of high importance for the increasing [...]- 0
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- E. Aria, J. Olstam, C. SchwieteringCollection of Transportation Research Procedia (2017).
Abstract
Advanced Driver Assistance Systems (ADAS) offer the possibility of helping drivers to fulfill their driving tasks. Automated vehicles (AV) are capable of communicating with surrounding vehicles (V2V) and infrastructure (V2I) in order to collect and provide essential information about the driving environment. Studies have proved that automated driving have the potential to decrease traffic congestion by reducing the time headway (THW), enhancing the traffic capacity and improving the safety margins in car following. Despite different encouraging factors, automated driving raise some concerns such as possible loss of situation awareness, overreliance on automation and system failure. This paper aims to investigate the effects of AV on driver’s behavior and traffic performance. A literature review was conducted to examine the AV effects on driver’s behavior. Findings from the literature survey reveal that conventional vehicles (CV), i.e. human driven, which are driving close to a platoon of AV with short THW, tend to reduce their THW and spend more time under their critical THW. Additionally, driving highly AV reduce situation awareness and can intensify driver drowsiness, exclusively in light traffic. In order to investigate the influences of AV on traffic performance, a simulation case study consisting of a 100% AV scenario and a 100% CV scenario was performed using microscopic traffic simulation. Outputs of this simulation study reveal that the positive effects of AV on roads are especially highlighted when the network is crowded (e.g. peak hours). This can definitely count as a constructive point for the future of road networks with higher demands. In details, average density of autobahn segment remarkably improved by 8.09% during p.m. peak hours in the AV scenario, while the average travel speed enhanced relatively by 8.48%. As a consequent, the average travel time improved by 9.00% in the AV scenario. The outcome of this study jointly with the previous driving simulator studies illustrates a successful practice of microscopic traffic simulation to investigate the effects of AV. However, further development of the microscopic traffic simulation models are required and further investigations of mixed traffic situation with AV and CV need to be conducted.Abstract
Advanced Driver Assistance Systems (ADAS) offer the possibility of helping drivers to fulfill their driving tasks. Automated vehicles (AV) are capable of communicating with [...]- 0
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- E. Misokefalou, F. Papadimitriou, P. Kopelias, N. EliouCollection of Transportation Research Procedia (2017).
Abstract
Over the last years, distracted driving possesses a leading position among accident causes and it constitutes an increasing road safety problem with disastrous results. Considering external factors of distraction as highly significant, they can be grouped in four categories: built roadway, situational entities, natural environment, and built environment. The fourth category, related to civil infrastructure and commercial land use, combined with high vehicle speeds that occur in motorways, might contribute to the creation of a very dangerous environment, increasing driver distraction and inattention. Through accurate research, solid results can emerge and traffic safety can be enhanced. The present study deals with driver distraction caused by out-of-the-vehicle factors, as well as factors related to the driver, such as age, gender, driving experience etc. It covers the distraction of driver attention during driving due to external factors that are not related to the main task of driving, resulting in impairments to driver attention and decision-making ability and hence the driver’s overall performance. For this purpose, we assess the side effects of numerous road elements, such as information signs, roadside advertising, Variable Message Signs, toll buildings, noise barriers/panels etc. to driver attention. The study is based on a medium-scale experimental procedure which took place in Attica Tollway, the Ring Road of the Athens metropolitan area, which was part of a larger research project conducted by the University of Thessaly, Department of Civil Engineering that included a total of three urban freeways in Greece. In order to create the appropriate research basis and to use as reliable data as possible, the gaze tracker FaceLab software was used on a sample of 29 drivers. Each participant drove 51 km on Attica Tollway, both in level terrain with 3 lanes and speed limit up to 120 km/h and in rolling terrain with 2 lanes and speed limit up to 80 km/h. The distraction of driver attention is evaluated via a continuous recording of his/her gaze, which acts as the main indicator regarding driver performance. The results of this procedure, analyzed via Captive software, are focused on the time that the driver’s gaze remained on each of the road elements under research. The analysis offers conclusions on different aspects - driver, road element and the road in total - comparing and categorizing the results by using a 4-level timescale from 0 to 2 seconds. This study can be used as a tool that can help in understanding and limiting the use of roadside elements that are not related to the execution of the driving task, but that may serve as potential causes of distraction. The results of this type of research procedures are very useful in preventing the forthcoming pressure for more billboards and trademarks on the roads, as well as in encouraging the adaptation of more precise regulations relating to the road infrastructure, the placement of roadside elements, etc.Abstract
Over the last years, distracted driving possesses a leading position among accident causes and it constitutes an increasing road safety problem with disastrous results. Considering [...]- 0
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- N. Faouzi, L. KleinCollection of Transportation Research Procedia (2017).
Abstract
Intelligent transportation system (ITS) infrastructures contain sensors, data processing, and communication technologies that assist in improving passenger safety, reducing travel time and fuel consumption, and decreasing incident detection time. Multisource data from Bluetooth® and IP-based (cellular and Wi-Fi) communications, global positioning system (GPS) devices, cell phones, probe vehicles, license plate readers, infrastructure-based traffic-flow sensors, and in the future, connected vehicles enable multisource data fusion to be exploited to produce an enhanced interpretation of the monitored or observed situation. This occurs by decreasing the uncertainty present in individual source data. Although demonstrated for more than two decades, data fusion (DF) is still an emergent field as related to day-to-day traffic management operations. Data fusion techniques applied to date include Bayesian inference, Dempster-Shafer evidential reasoning, artificial neural networks, fuzzy logic, and Kalman filtering. This paper provides a survey of ITS DF applications, including ramp metering, pedestrian crossing, automatic incident detection, travel time prediction, adaptive signal control, and crash analysis and prevention, and indicates directions for future research. The encouraging results so far should not conceal the challenges that remain before widespread operational deployment of DF in transportation management occurs.Abstract
Intelligent transportation system (ITS) infrastructures contain sensors, data processing, and communication technologies that assist in improving passenger safety, reducing [...]- 0
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- D. Jolovic, A. Stevanovic, S. Sajjadi, P. MartinCollection of Transportation Research Procedia (2017).
Abstract
The Highway Capacity Manual (HCM) 2015 freeway facilities methodology offers a supplemental computational engine FREEVAL, which is a macroscopic/mesoscopic tool that enables users to implement HCM-based freeway analysis quickly and conveniently. On the other hand, Vissim is a microscopic simulation tool that enables users to model real-world conditions with high level of accuracy and comprehensiveness. Thus, the two tools represent quite opposite sides in freeway modelling – Vissim requires time-consuming preparation and calibration of the model but it usually provides benefits that are more comprehensive. FREEVAL requires less on input and calibration sides but its results may not be as beneficial as comprehensive and accurate as Vissim’s. The problem, that has not been addressed enough, is that we do not know how different their results are (when compared between themselves) and, at the same time, how close to the field conditions. Researchers and practitioners use both tools for freeway analysis and tend to compare the results directly. One of the commonly used performance measures is the Level of Service (LOS), which is used to quickly evaluate the freeway segment or facility performance. The HCM Freeway Facility Methodology uses density to estimate LOS. However, density is calculated differently in FREEVAL and Vissim, and comparing the estimated LOSs between the two may not represent a proper comparison. In essence, FREEVAL, in the under-saturated condition, estimates the density from the fundamental equations where the volume is estimated from the user entered demand and the speed is calculated using the statistical models provided in respective chapters of each segment type. On the other hand, Vissim tracks each individual vehicle as it moves along a freeway and calculates key performance measures by using individually modeled driver’s behavior. This paper aims to compare and contrast the methodologies behind the two tools and offer explanation and discussion of their outputs. The paper will cover four major HCM freeway segment types (basic, merge, diverge, and weaving) in under-saturated conditions. Field data will be acquired from a section of I-880 freeway in California. FREEVAL and Vissim models will be calibrated and validated using Mobile Century Data provided by University of California at Berkley and Caltrans Performance Measurement System. The output of both tools will be evaluated against the field data. The assessment should reveal the ability of each tool to replicate the real-world conditions. Paper results will contribute to the existing body of knowledge by filling the gap in the literature related to comparison and contrast of the key (LOS-related) performance measures of these two tools.Abstract
The Highway Capacity Manual (HCM) 2015 freeway facilities methodology offers a supplemental computational engine FREEVAL, which is a macroscopic/mesoscopic tool that enables [...]- 0
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- N. Heiden, J. GeistefeldtCollection of Transportation Research Procedia (2017).
Abstract
Work zones considerably influence the traffic flow quality on freeways. In work zones, the capacity can be significantly reduced due to narrower lanes, a reduced number of traffic lanes, and unfavorable roadway geometry. In order to evaluate the impact of work zones on congestion occurrence and resulting delays as well as to allow for a consideration of alternative work zone layouts in the planning process, models to estimate the capacity of work zones are required. The paper presents results from a comprehensive study of work zone capacity on German freeways. In the analysis, a large number of short-term work zones with temporary lane closures as well as long-time work zones with and without a reduction of the number of lanes were covered. Data from loop or radar detectors upstream of the work zones were analyzed. For the capacity estimation of long-term work zones, both deterministic and stochastic approaches were used. In contrast to long-term work zones, traffic flow data measured at short-term work zones include only one traffic breakdown observation in most cases. This breakdown often occurs immediately after the lane closure, which means that the pre-breakdown volume does not represent the capacity of the work zone. Hence, valid capacity estimates could only be determined for the post-breakdown congestion outflow. The estimated capacities were analyzed regarding the influence of the traffic, geometric and control conditions in the work zone. Relevant parameters are the number of lanes, the lane widths, the existence of divided lanes, the existence of a lane reduction as well as the share of commuters and heavy vehicles. For short-time work zones, also the side of the lane closure (left or right lane) has an influence on the capacity. As a result of the study, capacity estimation models for both short- and long-term work zones, which can be applied in work zone planning procedures, are provided.Abstract
Work zones considerably influence the traffic flow quality on freeways. In work zones, the capacity can be significantly reduced due to narrower lanes, a reduced number of [...]- 0
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- G. Andrade, C. Pitombo, A. Cunha, J. SettiCollection of Transportation Research Procedia (2017).
Abstract
Free flow speed (FFS) is defined in the HCM as the “average speed of vehicles on a given segment, measured under low-volume conditions, when drivers are free to travel at their desired speed and are not constrained by the presence of other vehicles or downstream traffic control devices”. FFS is a very important parameter for the estimation of LOS and capacity for uninterrupted highways facilities. Ideally, FFS is determined using field measurements, but the HCM 2010 provides models for its estimation, when field data is not available. Such models must be recalibrated for local conditions when the HCM 2010 is adapted for use in countries outside North America. In this paper, Multivariate Analysis (MVA) techniques are used to investigate which infrastructure characteristics are related to FFS on Brazilian expressway facility segments, in order to provide a framework for the development of models to replace those used in HCM 2010 to estimate FFS. This study used a database with a large number of speed-flow observations obtained at 36 sites on Brazilian expressways (freeways and divided multilane highways), along with information on seven variables describing segment characteristics such as: expressway type, roadside environment, number of lanes, rise and fall, bendiness, access point density, and posted speed limit for passenger cars. Principal Component Analysis (PCA) was used to select the variables to be included in the proposed model. The results of the PCA indicated that three components are responsible for most of the variance on observed FFS: (1) posted speed, (2) the combined effects of road class, number of lanes and density of access points, and (3) the interaction of geometric design and roadside environment. Stepwise linear regression was used to fit a FFS model from these three components. This model was mathematically manipulated to provide a FFS that is structurally similar to the one used by HCM 2010 but in fact accounts for the interactions among variables. The proposed model can replace the HCM 2010 model and does not require the user to choose an initial value for the base FFS.Abstract
Free flow speed (FFS) is defined in the HCM as the “average speed of vehicles on a given segment, measured under low-volume conditions, when drivers are free to travel at [...]- 0
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- D. Hale, A. Hajbabaie, J. Ma, J. Hu, H. Park, J. BaredCollection of Transportation Research Procedia (2017).
Abstract
To justify investments towards improved traffic operations, engineers and policy-makers need scientific and accurate methods of congestion measurement. However, status-quo methods are limited and/or outdated. Peak-hour analyses are becoming outdated as a sole source of traffic assessment, because they fail to account for changing conditions throughout the year. There has been a movement towards “reliability” modeling, which attempts to capture these annual effects. But due to significant input data and calibration requirements, the reliability models suffer from practicality issues. Next, there have been recent improvements in data-driven ITS technologies, which identify congestion in real time. However, there is room for improvement in the robustness of performance measures derived from these technologies. Finally, some engineers have compared and ranked congested locations (i.e., bottlenecks) on the basis of experience and judgment. Despite their cost-effectiveness, judgment-based qualitative assessments will lack credibility unless backed by quantitative results. In a recent Federal Highway Administration study, congestion measurement was a primary area of emphasis. This paper discusses project-specific software development, which produced new and innovative performance measures for congestion measurement. It will present concepts and evidence to imply superiority of the proposed new measures. This paper is intended to serve as a preview of a future full journal paper, which will rank ten or more real-world bottlenecks according to new and old performance measures, to demonstrate impacts of the new measures. It is hoped that the new performance measures will be adopted by states and/or commercial products, for a new level of robustness in congestion measurement.Abstract
To justify investments towards improved traffic operations, engineers and policy-makers need scientific and accurate methods of congestion measurement. However, status-quo [...]- 0
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- D. Yamaguchi, T. Okano, H. Sudo, M. Kobayashi, T. Ogihara, N. Izumi, A. Tanaka, T. YoshiiCollection of Transportation Research Procedia (2017).
Abstract
This study investigates various factors that cause the reduction of discharge flow at a bottleneck on an urban expressway. The current worst bottleneck on Tokyo Metropolitan Expressway Network seems to be combined complicate factors that affect the discharge flow at the bottleneck. 5 causing factors, merging ratio, longitudinal gradient, duration time involved in congestion, environment of backlight and brightness are considered, and the impact of these 5 causing factors are investigated. Then the results supported the hypothesis that all of the 5 causing factors affect the discharge flow rate.Abstract
This study investigates various factors that cause the reduction of discharge flow at a bottleneck on an urban expressway. The current worst bottleneck on Tokyo Metropolitan [...]- 0
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- C. Schwietering, M. FeldgesCollection of Transportation Research Procedia (2017).
Abstract
Long-term roadworks on highways are vital as part of carriageway and bridge renovations. They generate bottlenecks and consequently congestion and accidents. If the number of lanes is reduced, it can also lead to significant capacity decrease. Even if it is ensured that all lanes are kept operative, narrow lanes and transitions will affect the capacity. The impact of roadworks on capacity have been analysed in detail by [BECK_2001]. Therefore, intelligent solutions to support the traffic flow at long-term roadworks bottlenecks have to be evaluated. For this purpose the TrafficChange concept was developed. TrafficChange describes the modules of tidal flows on long-term roadworks: - Module 1: Tidal Flow basic set - TrafficChange SE (quickly repositionable moveable safety barriers, so-called Quick-Change Moveable Barriers (QMB)) - Module 2: Attached Traffic Safety Equipment for Tidal Flow - TrafficChange VT including data collection, traffic monitoring, communication, energy supply and displays - Module 3: Repositionable congestion warning systems to safeguard congestion - Module 4: Core system for data analysis, monitoring and managing traffic (TrafficChange Center) as cloud-based service With these components, a dynamic assignment of lanes to higher demanded direction can be reached. Main application fields of TrafficChange are: - Maintenance of bridges - Renewal of road pavement, road surface restoration (entire carriageway) - Tunnel renovation with two-way traffic in the operational tube - Temporarily adaption of the number of operational lanes in dependency of the traffic demand in order to enlarge working space of a roadworks The use of TrafficChange has beneficial effects on capacity and thus on traffic flow. In case of traffic lane reduction due to roadworks, TrafficChange can dynamically assign the remaining traffic lanes according to the demand of both driving directions. Even if all traffic lanes are kept operational during the roadworks, TrafficChange provides several advantages. In case of roadworks on a six lane facility (three lanes in both directions), usually one lane has to be managed separately on the carriageway of the construction field. This has a massive negative impact on the roadworks progress and the completion timetable. When applying TrafficChange this single separate lane is not necessary. Simultaneously this leads to significant capacity increase for this lane, since all lanes are managed on one carriageway and overtaking opportunity is provided. Evaluations of roadworks in Germany have shown that using TrafficChange will enhance the capacity by 10-15% for the driving direction of the construction site. One the other hand, for the direction with low demand, capacity is reduced temporarily, since one lane less is available. When demand for this period is low and can be managed by using the remaining lanes, the traffic flow quality stays efficient. For an economically efficient use of TrafficChange, the demand peaks should not occur simultaneously in both directions. Therefore, for each roadworks it needs to be evaluated individually whether TrafficChange can efficiently improve the traffic flow. For evaluation of the effects, the TrafficChange system is implemented in a microscopic traffic simulation tool, which can be adapted easily for different settings of the roadworks to be evaluated. As input values, the number of available lanes, roadworks design, traffic demand for each required scenario (such as weekday, weekend, holiday) and the length and planned duration of the roadworks are required. As key values, the simulation determines the congestion length, congestion duration and delay times. With these values, the benefit of TrafficChange can be determined. The efficiency estimation is determined by accumulation of total delay times for each required scenario, multiplied by the amount of days this scenario occurs during the roadworks is active, for both the comparison case (roadworks without TC) and target scenario (roadworks with TC). By using current travel time expenses for passenger cars and heavy vehicles, the benefit can be expressed in costs. By the use of TrafficChange, the entire carriageway can be closed so that considerable savings of working period and economic losses could be achieved although the number of operative lanes is lower than in the comparison case. The TrafficChange concept leads to improved traffic safety and optimized traffic flow at roadworks as well as reduced roadworks duration and therefore high economic efficiency that can be determined by the simulation tool TCSim. Literature [BECK_2001] - Beckmann, A., Zackor, H. (2001): Study and calibration of procedures for current estimation of the duration and length of traffic jams as a result of single-day and long-term construction sites on motorways, Forschung Straßenbau und Straßenverkehrstechnik, Volume 808, Bonn, Germany, 2001 [EASY_2009] - Easyway (2009) : Mobile Congestion Warning Systems at lorm term roadworks increase traffic safety – Efficiency of Mobile Congestion Warning Systems, Offprint of the ‘Landestelle für Straßentechnik Baden-Württemberg’, Stuttgart, 2009, www.easyway-its.eu [SUEM_2012] - Sümmermann, A. (2012): Examination of traffic safety and traffic flow in work zones on German Motorways, Aachener Mitteilungen Straßenwesen, Erd- und Tunnelbau, Volume 59, Aachen 2012 [VOLK_2014] - Volkenhoff, T. (2014): Model-based derivation of operating conditions of a video-aided incident and work zone management system in construction sites on German motorways, Aachener Mitteilungen Straßenwesen, Erd- und Tunnelbau, Volume 61, Aachen 2014 [HMSV_2012] – HMSV (2012): Congestion Evaluation 2011. Hessen Mobil – Straßen- und Verkehrsmanagement. URL: http://www.staufreieshessen2015.de, requested on 04.07.2012Abstract
Long-term roadworks on highways are vital as part of carriageway and bridge renovations. They generate bottlenecks and consequently congestion and accidents. If the number [...]- 0
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- B. Kuhn, K. Balke, R. Brydia, L. Theiss, I. Tsapakis, L. Ruback, M. LeCollection of Transportation Research Procedia (2017).
Abstract
In May 2013, the regular session of the 83rd Texas State Legislature passed House Bill (HB) 2204 related to the establishment of a variable speed limits (VSL) pilot program by the Texas Transportation Commission. The bill was signed into law by the governor in June 2013. In December 2013, the Texas Transportation Commission established Rule §25.27 of the Texas Administrative Code authorizing and requiring the Texas Department of Transportation (TxDOT) to implement a variable speed limit pilot program to “study the effectiveness of temporarily lowering prima facie speed limits to address inclement weather, congestion, road construction, or any other condition that affects the safe and orderly movement of traffic on a roadway.” The goal of the pilot program was to deploy VSL in up to three locations to test the concept under three operational conditions and to determine the impacts of VSL on facility operations and safety. The specific objectives of the pilot project evaluation were to determine how much congestion was reduced in the area impacted by the implementation of VSL, to understand the users’ perceptions of the VSL systems, to assess the safety impacts of VSL, and to determine the overall costs and benefits of VSLs. Up until this point in time, VSL was not a legal alternative for freeway operations in Texas. After the bill was passed, TxDOT worked with the Texas A&M Transportation Institute (TTI) in selecting pilot project sites for the development, implementation, and evaluation of VSL. The VSL systems were to be used for the purpose of controlling speeds at sites that have (a) construction work zones, (b) weather-related events, and (c) urban congestion. This paper presents the overall approach to the development, implementation, and operation of the VSL pilot projects along with the analysis of the installations with respect to their impact on congestion, safety, users’ perception, violations, and benefit-cost of the projects. It also presents a number of lessons learned throughout the course of the pilot tests that provide beneficial insight into how to improve similar projects for permanent installations. Based upon the limited data available for the VSL pilot project, it was determined that VSLs would be beneficial if implemented to address inclement weather, congestion or road construction. VSLs had a safety benefit at each location and motorists had a clear understanding of the purpose of the VSLs.Abstract
In May 2013, the regular session of the 83rd Texas State Legislature passed House Bill (HB) 2204 related to the establishment of a variable speed limits (VSL) pilot program [...]- 0
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- J. Bakaba, J. OrtleppCollection of Transportation Research Procedia (2017).
Abstract
Roadwork zones interrupt the flow of traffic and shall reduce road safety of motorways (autobahns), at least in specific sections. Motorways are the fastest roads in the German roadwork and have the highest level of safety – higher than either roads inside built-up areas or other roads outside built-up areas. Nevertheless, a total of 17, 172 accidents involving personal injury occurred on motorways in the year 2011, 1, 118 of them at roadwork zones. A total of 18 people were killed and 220 seriously injured. The principal aim of this research project was to find out if either roadwork zones on motorways are more unsafe than other motorways sections or they are specific subsections inside of roadwork zones or near them which are particularly unsafe. The research project consisted of an analysis of the statistics in the vicinity of all roadwork zones on German motorways (autobahns). Road accidents recorded by the police for a period of at least 12 months at 76 selected roadwork zones and a retrospective accident analysis of 12 completed motorway roadwork zones were macroscopic analyzed. In addition, a microscopic analysis of the accident occurrence was carried out of eight existing roadwork zones with a total length of 57 km and included also the analysis of the driving behavior of car and truck drivers throughout the length of the roadwork zones and/or in characteristic subsections in or near them. The results of the research project confirm that accidents at roadwork zones on motorways are generally accidents involving minor damage to property. The accident severity (fatalities per 1, 000 accidents involving personal injury) of accidents that occur on sections of motorway without roadwork zones is up to 1.6 times higher than that of accidents that occur at roadwork zones. The study shows different accident rates and accident cost rates for some characteristic subsections along the roadwork site. Nevertheless, there are problem areas in terms of road safety, particularly at the beginning and end of roadwork zones, lane realignment points, carriageway changeover points and temporary slip roads. These characteristic subsections of roadwork zones have an influence on the road safety. The same applies to the impact of how the traffic is routed, the length of the roadwork site or specific road equipment (e.g. road signs against a yellow background).Abstract
Roadwork zones interrupt the flow of traffic and shall reduce road safety of motorways (autobahns), at least in specific sections. Motorways are the fastest roads in the German [...]- 0
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- A. Goto, H. NakamuraCollection of Transportation Research Procedia (2017).
Abstract
Functional hierarchy of road network classifies individual roads into several levels by taking account of the priority for mobility, access or residential functions, in order to manage traffic efficiently by segregating through traffic from accessing, parking and non-motorized traffics. This concept has been widely recognized and applied to road planning, design and operation in several countries such as Germany, the US and Australia. Their guidelines state the target performances (i.e., LOS or travel speed in general) of each hierarchical levels being used for the performance evaluation. However in Japan, target performances of roads are not shown in the current guideline, since a concept of the performance-oriented planning and design is still uncommon in practice. As a result, the operational performances are still not satisfactory enough especially on highways. In such a situation, this study attempts to find out the hierarchical road classification applicable to Japan, considering the distribution of region/district centers as well as the impact of terrain. The main questions are how many hierarchical levels need to be defined and how much travel speed and road spacing (or access distance) should be set as the targets for each level, so that the network performance, namely travel time between region/district centers, can achieve the given target values. The basic idea comes from the German guideline RIN, which states the target travel times by region/district center (central place), classifies roads and define their target travel speeds based on their connecting centers. However, it does not clearly mention how the difference in distribution of region/district centers and the impact of terrain can be reflected to set the efficient hierarchical classification. For example, the characteristic of metropolitan areas is quite different from that of mountainous areas in terms of trip lengths between region/district centers of which travel times are to be evaluated as network performance. In addition, because of the impact of terrain, construction cost per unit is generally quite higher in mountainous areas than in flat areas, whereas travel demand is usually lower in mountainous areas. This study incorporates these issues into road classification and demonstrates its impact for more efficient network system planning. The methodology consists of four steps: (1) defining the region/district centers to be connected and setting their target travel time, (2) developing alternative road classification scenarios, (3) mathematically formulating origin-destination travel time in a grid road network under the certain classification and (4) evaluating the classification scenarios considering the difference of average trip lengths of each combination of centers as well as the difference of system cost due to the impact of terrain and travel demand. Although the original intention of this study is to apply the result to Japan, the methodology itself is generally applicable to any region. At the end, case studies are conducted for several simplified areas for reflecting their typical characteristics of region/district centers distribution and terrain in Japan. Through them, the hierarchical road classifications by area type are suggested as a conclusion.Abstract
Functional hierarchy of road network classifies individual roads into several levels by taking account of the priority for mobility, access or residential functions, in order [...]- 0
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- A. Kendziorra, P. Wagner, T. ToledoCollection of Transportation Research Procedia (2017).
Abstract
Car-following models are an essential part of microscopic traffic simulations. For research regarding traffic safety, traffic simulations need to simulate traffic safety related aspects realistically. That means, for example, accidents and near accidents shall occur in the same quantity and in the same way as in reality. Such simulations can be used to make statements about traffic safety with respect to traffic influencing factors and conditions. However, most car-following models are deterministic and do not incorporate uncertainty and fluctuations of perception and behavior. Also, they are explicitly conflict free. Therefore, they are unsuitable for simulating traffic in the desired way. For that reason, a car following model fulfilling the requirements above was developed. Inspired by [1], our car-following model is nondeterministic and data-driven. It is based on the data set of the Intelligent Cruise Control Field Operational Test [2], in which instrumented vehicles have been used by 108 voluntary drivers for several weeks yielding trajectories of approximately 88, 000 driving kilometres. In our model, the acceleration a of a vehicle depends on the following input: -v, the velocity of the vehicle, -∆v, the difference between the velocity of the preceding vehicle and its own velocity, -g, the gap between the vehicle and the preceding vehicle and -aL, the acceleration of the preceding vehicle. The acceleration a underlies a probability distribution that depends on v, ∆v, g and aL. That means, if v*, ∆v*, g* and aL* are the current values for v, ∆v, g and aL, then there exist a probability distribution F(v*, ∆v*, g*, aL*) and the actual acceleration a will be drawn from F(v*, ∆v*, g*, aL*). For each tuple (v, ∆v, g, aL), the probability distribution F(v, ∆v, g, aL) was determined by the data of the FOT. For that, the data of velocity, velocity difference, gap and acceleration of the preceding vehicle were binned, and for each tuple (v, ∆v, g, aL) of binned values, the expected acceleration, the variance and the type of distribution were computed and stored in look-up tables. During a simulation, the probability distribution F(v, ∆v, g, aL) to a given tuple (v, ∆v, g, aL) can be recovered by these look-up tables. To achieve probability distributions that result in a well behaving car-following model, the data had to be corrected (due to erroneous sensor data) and filtered (due to situations in which the driver reacted to other influences besides the preceding vehicle, e.g. red traffic lights) in numerous steps. Here, we will present the mentioned correction and filtering steps in detail. Further, we will discuss the derived probability distributions and the calibration of the model. Finally, the model will be evaluated and compared to other existing car-following models in several scenarios with respect to various criteria, e.g. the number of accidents, the distribution of surrogate safety measures, and the fundamental diagram.Abstract
Car-following models are an essential part of microscopic traffic simulations. For research regarding traffic safety, traffic simulations need to simulate traffic safety related [...]- 0
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- A. Haug, S. GrosanicCollection of Transportation Research Procedia (2017).
Abstract
Within section control systems on motorways drivers get information about adequate speed limits during adverse weather situations. Therefore road weather data are necessary. To detect the danger of aqua-planning measurements of precipitation intensity and waterfilm thickness as well as the status of the road surface are needed. To detect these atmospheric data different weather sensors are located near the motorway. There are two different sensor systems available which detect these measurements at the moment. For the detection of the status of the road surface, like dry, moist or wet, the sensor is imbedded directly in the road surface in most cases. The other sensor system is non-invasive which can be installed next to or over the road. Nowadays more and more open-pored asphalt is used because of its advantage to be less noisy and its property to drain off water better than normal asphalt. But this kind of asphalt cannot be cut to install a road sensor therefore the usage of non-invasive sensors will be increase in the future. This may also lead to different thresholds in automatic traffic control during adverse weather situations. The measurements of waterfilm thickness, road surface and road temperature are very important for automatic traffic control algorithms [2] as a speed limit caused by rain is derived and shown on variable message signs. In the German Technical Bulletin [2] a matrix with the two measurements precipitation intensity and water film thickness define which wetness-level is detected. There are 5 wetness-levels which cause different speed limits. For the first supply thresholds are given based on the experiences with road sensors. For the newer non-invasive sensors other thresholds may be necessary. This paper will show some possible thresholds for the precipitation/waterfilm thickness matrix and their effects on the speed limits shown on the variable massage signs. Within the German Test Site for Road Weather Stations [1] various road sensors as well as various non-invasive sensors are installed. The data for both detection technologies has been collected for the last 2 years and allows a statistically valid comparison of them. In this paper the advantage and disadvantage of the two sensor technologies will be shown for the measurements waterfilm thickness, road surface and road temperature. In order to describe the behavior of the sensors, the available data will be analyzed concerning the availability of valid datasets and the accuracy. Additionally the performance of the sensors is examined during periods of different clusters of traffic volumes.Abstract
Within section control systems on motorways drivers get information about adequate speed limits during adverse weather situations. Therefore road weather data are necessary. [...]- 0
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- A. Kondyli, P. Gubbala, L. ElefteriadouCollection of Transportation Research Procedia (2017).
Abstract
Transportation engineers rely on the Highway Capacity Manual (HCM) for estimating capacity at freeway segments. According to the HCM 2010, the capacity of the basic freeway segments is a function of the free-flow speed and it ranges from 2, 400 passenger cars per hour per lane (pc/h/ln) for FFS 70 or 75 mi/h, to 2, 250 pc/h/ln for FFS 55 mi/h. The freeway merge segments methodology in the HCM 2010 Update uses these same capacity values in the analysis procedure, although research has shown that capacities at these bottleneck locations are considerably lower. In addition to that, researchers have also observed that capacity varies significantly from day to day and from one site to the other. Researchers acknowledge that driver behavior and frequent interactions between mainline and ramp vehicles at these junctions are the causal factor of these variations in capacity and the low capacity values, however, this has not been reflected in the updated version of the HCM 2010. Furthermore, the HCM 2010 Update does not account for the conflicting movements and the contribution of the ramp vehicles on the overall merge junction capacity. This paper investigates the relationship between freeway and ramp demand and capacity at merge junctions. For the purposes of this research, historic data at merge bottleneck locations across North America with different geometric and operational characteristics were analyzed. The results of the analysis show that, there is a clear correlation between ramp demand, freeway demand and freeway capacity. More specifically, higher demand on the on-ramps produces lower overall capacity values. In addition, this paper proposes new capacity values for merge junctions as a function of the freeway and ramp demand and number of lanes.Abstract
Transportation engineers rely on the Highway Capacity Manual (HCM) for estimating capacity at freeway segments. According to the HCM 2010, the capacity of the basic freeway [...]- 0
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- A. Skabardonis, F. Papadimitriou, B. Halkias, P. KopeliasCollection of Transportation Research Procedia (2017).
Abstract
The paper presents the findings to date of operational analyses at freeway off-ramps with emphasis on analysis procedures on recurrent off-ramp bottleneck locations at the Attiki odos motorway (Attica Tollway) in Athens, Greece. We compared the observed traffic performance metrics at two sites with the predicted measures using the methodology of freeway diverge areas and weaving sections in the 2010 edition of Highway Capacity Manual (HCM) for a wide range of traffic conditions. The findings indicate that the HCM volume predictions at the diverge area are in close agreement with field data and the density is underestimated by 7% on the average. The HCM weaving analysis methodology underestimated the weaving section capacity especially for high weaving volumes, and overestimated the section density by 17% on the average.Abstract
The paper presents the findings to date of operational analyses at freeway off-ramps with emphasis on analysis procedures on recurrent off-ramp bottleneck locations at the [...]- 0
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- R. AkcelikCollection of Transportation Research Procedia (2017).
Abstract
This paper compares two analytical approaches for modelling signalised intersection networks in relation to the assessment of signal coordination quality as a fundamental element of network performance analysis. These are (i) the traditional model based on using “lane groups” or “links” through aggregation of individual lane conditions, and (ii) a new “lane-based” model of upstream departure and downstream arrival patterns as well as midblock lane changes between upstream and downstream intersections, and the resulting proportions of traffic arriving during the green period at an individual lane level. The latter is part of a lane-based network model that involves blockage of upstream intersection lanes by downstream queues (queue spillback) and capacity constraint applied to oversaturated upstream intersections. The differences between the two models are expected to be particularly important in evaluating closely-spaced intersections with high demand flows where vehicles have limited opportunities for lane changes between intersections. The lane-based model can make use of “special movement classes” (e.g. through movements at external approaches which become turning movements at downstream internal approaches, and the dogleg movements at staggered T intersections) to enhance the modelling of signal platoon patterns. This allows assignment of specific movements to separate lanes and separate signal phases, and tracking of their second-by-second platoon patterns through the network separately. The method also allows better estimation of unequal lane use cases at closely-spaced (paired) intersection systems, a factor which also affects signal platoon patterns. The paper presents a staggered T network example to demonstrate important aspects of modelling signal platoon patterns by approach lane use and movement class, and to compare the resulting traffic performance measures (delay, back of queue, level of service) with those estimated using the traditional method based on lane groups or links.Abstract
This paper compares two analytical approaches for modelling signalised intersection networks in relation to the assessment of signal coordination quality as a fundamental [...]- 0
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- A. Keegan, E. GonzalesCollection of Transportation Research Procedia (2017).
Abstract
Freight deliveries on signalized urban streets are known to cause lane blockages during delivery. Traffic congestion associated with urban freight deliveries has gained increasing attention recently as traffic engineers and planners are tasked with finding solutions to manage increasing demand more sustainably with limited road capacity. The goal of this research is to evaluate two models for quantifying the capacity and delay effects of a lane blocking freight delivery on a signalized urban street. The two methods are: an all-or-nothing model similar to methodology used in the Highway Capacity Manual 2010 (HCM2010) and a detailed analytical model consistent with kinematic wave theory. The purpose is to provide insight on the use of these tools for analysis of urban freight delivery policy. The results of the two models are compared with each. A simulation of 8th Avenue in New York has been calibrated to observed freight deliveries from a six-hour period, and the simulated results confirm effect of delivery location on capacity and delay. The results show that the methods from the HCM2010 to account for the effects of buses stopping for passengers provide only a coarse representation of the capacity and delay effects of urban freight deliveries. The more detailed approach that accounts for the dynamics of queuing provide closed form analytical formulas for delay and capacity that can account for varying locations of deliveries, long delivery durations, and different impacts on different lane groups.Abstract
Freight deliveries on signalized urban streets are known to cause lane blockages during delivery. Traffic congestion associated with urban freight deliveries has gained increasing [...]- 0
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