Documents published in Scipedia

• A Methodology for Signal Timing Estimation Based on Low Frequency Floating Car Data: Analysis of Needed Sample Sizes and Influencing Factors

  S. Axer, B. Friedrich

  Collection 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 [...]

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• Traffic Flow Quality from the Users Perspective

  S. Hohmann, J. Geistefeldt

  Collection 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 [...]

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• The Development and Practice of China Highway Capacity Research

  R. Zhou, L. Zhong, N. Zhao, J. Fang, H. Chai, J. Zhou, W. Li, B. Li

  Collection 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” [...]

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• Managing Motorways and Urban Arterials in Australia: Country Report for Australia

  R. Troutbeck, D. Walsh, M. Blogg

  Collection 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 [...]

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• Preparing a Roadmap for Connected Vehicle/Cooperative Systems Deployment Scenarios: Case Study of the State of Oregon, USA

  R. Bertini, H. Wang, T. Knudson, K. Carstens

  Collection 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 [...]

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• Development of a Mobility-Based Service Measure for Freeway Facilities

  R. Margiotta, D. McLeod, T. Scorsone

  Collection 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 [...]

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• Performance Benefits of Connected Vehicles for Implementing Speed Harmonization

  R. Dowling, B. Nevers, A. Jia, A. Skabardonis, C. Krause, M. Vasudevan

  Collection 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 [...]

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• The Influence of General Purpose Lane Traffic on Managed Lane Speeds: An Operational Study in Houston, Texas

  R. Avelar, K. Fitzpatrick, K. Dixon, T. Lindheimer

  Collection 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 [...]

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• Life Cycle Emissions and Cost Study of Light Duty Vehicles

  P. Prevedouros, L. Mitropoulos

  Collection 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 [...]

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• Expressway Traffic Demand Forecasts in the Volatile Economic Environment of Greece

  P. Prevedouros, B. Halkias

  Collection 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. [...]

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