Documents published in Scipedia

• A Multi-modal Approach for Highway Assessment

  M. Mailer

  Collection 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 [...]

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• Autonomous and Connected Cars: HCM Estimates for Freeways with Various Market Penetration Rates

  L. Shi, P. Prevedouros

  Collection 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 [...]

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• A Study of Collision Risk Estimation and Users Evaluation at Merging Section of Urban Expressway in Japan

  K. Suzuki, K. Imada, Y. Matsumura

  Collection 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 [...]

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• Methodology for Timing and Impact Analysis of Signalized Intersections

  K. Bang, J. Wahlstedt, L. Linse

  Collection 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 [...]

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• Effective Installation of an Auxiliary Lane at Sag Sections to Mitigate Motorway Traffic Congestion

  J. Xing, J. Tanaka

  Collection 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 [...]

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• Intelligent Controlled Compact Parking for Modern Parking Management on German Motorways

  J. Dierke, J. Kleine, R. Lehmann

  Collection 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 [...]

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• Variability of Capacity and Traffic Performance at Urban and Rural Signalised Intersections

  J. Chodur, K. Ostrowski, M. Tracz

  Collection 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 [...]

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• A Prediction Accuracy-Practicality Tradeoff Analysis of the State-of-the-art Safety Performance Assessment Methods

  J. So, S. Hoffmann, J. Lee, F. Busch, K. Choi

  Collection 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 [...]

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• Estimation Method for Interurban Accessibility: A Highway Performance Measure Indicating Smooth and Safe Traffic Flow

  H. Kita, H. Yotsutsuji, R. Asaka, J. Tsujitani, T. Watanabe

  Collection 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 [...]

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• Recent Developments and History of the Dutch HCM

  H. Heikoop, N. Henkens

  Collection 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 [...]

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