Documents published in Scipedia

• Traffic Flow at a Freeway Work Zone with Reversible Median Lane

  H. Waleczek, J. Geistefeldt, D. Cindric-Middendorf, G. Riegelhuth

  Collection 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 [...]

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• Capacity and Behaviour on One-way Cycle Tracks of Different Widths

  P. Greibe, T. Buch

  Collection 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 [...]

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• An Analysis of Express Lanes in Utah

  G. Schultz, S. Mineer, C. Hamblin

  Collection 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 [...]

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• Assessment of Basic Freeway Segments in the German Highway Capacity Manual HBS 2015 and Beyond

  J. Geistefeldt

  Collection 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 [...]

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• Evaluation of Driver Compliance to Displayed Variable Advisory Speed Limit Systems: Comparison between Germany and the U.S.

  G. Riggins, R. Bertini, W. Ackaah, M. Margreiter

  Collection 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 [...]

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• Evaluating the Service Quality in Multi-modal Transport Networks

  M. Friedrich

  Collection 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 [...]

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• Spatio-Temporal Congestion Patterns in Urban Traffic Networks

  F. Rempe, G. Huber, K. Bogenberger

  Collection 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 [...]

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• Investigation of Automated Vehicle Effects on Drivers Behavior and Traffic Performance

  E. Aria, J. Olstam, C. Schwietering

  Collection 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 [...]

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• Evaluating Driver Distraction Factors in Urban Motorways. A Naturalistic Study Conducted in Attica Tollway, Greece

  E. Misokefalou, F. Papadimitriou, P. Kopelias, N. Eliou

  Collection 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 [...]

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• Data Fusion for ITS: Techniques and Research Needs

  N. Faouzi, L. Klein

  Collection 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 [...]

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