Abstract: The Virginia Department of Transportation's (VDOT's) current policy is to use and accept from others the 1994 Highway Capacity Manual (HCM) as the basis for capacity analysis on Virginia's streets and highways. VDOT uses the latest version of the Highway Capacity Software (HCS). Software programs replicating the 1994 HCM may be used by others submitting work to VDOT for review; however, all input data and assumptions must be provided, and VDOT may use the HCS to check the submitted analysis. The analysis may be rejected if different results are obtained. To recommend appropriate revisions to this policy, this study evaluated computer software other than HCS that can be used in the analysis of signalized intersections, determining which programs provide acceptable results. The study then evaluated the results from simulation models to determine when and how to use this output in the analysis of signalized intersections. The study recommended that, in addition to HCS, VDOT use and accept from others SIGNAL94 and HCM/Cinema, or TRAF/NETSIM for capacity analysis at isolated intersections. CINCH, however, should not be used or accepted. For congested, oversaturated intersections, TRAF/NETSIM should be the preferred analysis type. Estimates of queue length at isolated signalized intersections should be derived from SIGNAL94, HCM/Cinema, or TRAF/NETSIM. For non-isolated intersections where queuing and spillback are a potential problem, simulation analysis with TRAF/NETSIM should be used instead of capacity analysis to determine the operational characteristics of the corridor.
Abstract: The objective of this study is to analyze the behavior of offsets between traffic signal subnetworks. If different cycle lengths are used for adjacent subnetworks, the relative timing between the subnetworks will deviate from the original setup. A generalized mathematical model is developed, which demonstrates the cyclic timing patterns of the offsets between subnetworks with different cycle lengths. The offset cycle time is equal to the Least Common Multiple (LCM) of the cycle lengths of the adjacent subnetworks. A TRAF-NETSIM model is used to examine how the cyclic behavior of offsets should be considering in timing the subnetworks, and in reconciling different offset requirements between more than two subnetworks.
Abstract: In this paper, an approach to real-time control of a network of signalized intersections is proposed based on a discrete time, stationary, Markov control model. The approach incorporates microscopic simulation of actuated controller output signals in response to probabilistic forecasts. An artificial neural network representation of vehicle delay estimations is proposed and tested for approximate real-time evaluation of potential traffic signal transitions.
Abstract: The road traffic simulation program SIMNET combines an event-orientated individual vehicle queueing model with a microscopic car-following-theory traffic flow model. Traffic demand is fully time dependent, and a large variety of traffic control measures is included in the model. Late developments include means for synchronization of the simulation with another parallel process. One of the latest model extensions and applications is the simulaiton of individual infrastructure-based dynamic route guidance (DRG), including the guidance network as it is known by the DRG central site (DRGCS), the communication between equipped vehicles and the DRGCS, and a set of travel time forecast and routing algorithms. Performance tests show clear benefits for DRG users at a penetration rate between 5% and 20%.
Abstract: This paper presents a case study of benefits, drawbacks and public reaction to installing traffic signals as neighborhood traffic control devices in Madison, Wisconsin. The study focused on a four lane undivided collector street which serves adjacent neighborhoods and is also a major route to the downtown area. Seven alternative traffic signal scenarios were evaluated with respect to progression, vehicle platoons, speed control, pedestrian crossing safety and gaps at unsignalized intersections. TRAF-NETSIM animation was used to illustrate the alternatives to the public. Traffic control diverters were studied and compared to traffic signals. In addition, guidelines for public presentation of traffic signals as a neighborhood traffic control device are discussed.
Abstract: A great need exists for lower-cost design strategies to reduce congestion on major suburban arterials on which conventional techniques have been exhausted. This study examines the possible gains in travel efficiency from three unconventional strategies: the median U-turn, in which left turns are made using crossovers on the arterial approximately 180 m from the main intersection; continuous green T-intersection (CGT), in which one or two lanes at the top of the "T" receive a constant green indication; and the North Carolina State University (NCSU) Bowtie, developed during the project, in which left-turning traffic uses roundabouts on the side street approximately 180 m from the main intersection. The study used Traf-Netsim 4.0 to simulate the unconventional configurations and a conventional intersection for comparison in three factorial experiments. The experiments showed that the unconventional alternatives have the potential to provide for more efficient travel. The CGT configurations reduced travel time and stops substantially at three-legged intersections for through volumes of more than 400 vehicles per hour per lane. The median U-turn became more efficient than the CGTs at higher through volumes. An experiment with a four-legged intersection showed that the NCSU Bowtie reduced travel time and stops from the conventional configuration at about 900 or more critical through vehicles per hour. Questions remain about the unconventional strategies, but that they potentially provide for more efficient travel is clear.
Abstract: Computer simulation has become an important tool for evaluating transportation strategies quickly and efficiently. Simulation is especially critical in assessing the potential of innovative traffic control alternatives. The calibration and validation of simulation models characterized by unconventional design and operation strategies is presented. This effort was part of a project to investigate unconventional traffic control alternatives for the North Carolina Department of Transportation. Three alternatives were selected for in-depth investigation: the Florida continuous green T-intersection, an application of the modern roundabout, and the Michigan median U-turn intersection. These strategies were examined using Traf-Netsim 4.0 and the macroscopic analysis package SIDRA 4.07. Models for each of the three alternatives were developed and efforts were made to calibrate and, in two cases, validate them with field data collected in Florida, Maryland, and Michigan. The highlights of the calibration included (a) updated critical gap distributions for the six-lane median U-turn and the roundabout, (b) a larger saturation flow rate for the median U-turn, (c) an average roundabout speed, and (d) a distribution of traffic into the free flow lane(s) for the continuous green T-intersection. The validation effort showed that the Traf-Netsim and SIDRA results compared reasonably well to field measurements.
Abstract: Computerized traffic signal design is composed of several steps: road network survey, traffic survey, control area determination, signal grouping, signal phasing design, signal timing generation, and signal performance evaluation. In the past years, most of the research efforts were focused on the topic of signal timing design. Little attention has been paid to those steps prior to the step of signal timing design, although they also have great effects on the optimization of computerized traffic signal design. The objective of this research is to develop a methodology for signal grouping. Factors affecting signal grouping are sorted out and examined. Relationships between the affecting factors and signal grouping are investigated. The qualitative guideline or quantitative threshold of each affecting factor is established. TRAF-NETSIM and TRANSYT-7F are used in a case study of urban street network to show the performance of a traffic control system with different ways of signal grouping. The effectiveness of the proposed methodology is evaluated and a computer-aided system has also been designed for the practical application of traffic engineers.
Abstract: With the emergence of Intelligent Transportation System (ITS) technologies, there has been a renewed interest in the bus priority signal (BPS). However, at present there is no model capable of simulating various BPS strategies and then restoring the original signal settings after bus preemption is awarded. The effect of providing the BPS treatment on the Washtenaw Avenue Corridor in Ann Arbor, Michigan was studied. The NETSIM graphic animation feature was used to detect the bus arrival, award preemption, and the signal timing plan was restored to the original setting manually. The model was calibrated using field data and the sensitivity of the model to several variables was tested. It was found that signal preemption disrupts traffic progression, and thus increases overall network vehicle and person delay. The bus travel time and delay were reduced when the optimal BPS plan was used. The BPS was tested under different network traffic volumes, different main to cross street traffic ratios for an isolated intersection, and signal preemption for carpools. It was found that maintaining progression is most critical under heavy traffic conditions. The traffic volume criteria that warrant signal preemption were established. There appears to be advantages to providing carpools with preemption capability up to between 5 and 10% of the main traffic volume.
Abstract: The principal goal of this study is to provide Texas Department of Transportation (TxDOT) engineers and officials with information and approaches that would assist in: 1) determining the potential of road pricing for urban congestion control, air quality enhancement, and revenue generation in Texas; and 2) developing a strategy for possible implementation of road pricing in Texas. Previous experience with congestion pricing in the U.S. and overseas is reviewed, revealing successful aspects as well as areas of concern. An integrated methodology for the evaluation of the networkwide traffic and air quality impacts of particular pricing schemes is developed. It is based on the DYNASMART dynamic simulation-assignment framework, expanded to incorporate specific user responses to pricing. An extensive stated preference survey of residents of Dallas, Houston, El Paso, and San Antonio is also conducted, indicating generally negative public attitudes towards pricing.
Abstract: This is the third paper in a series about the DRIVE II project PRIMAVERA, and presents the results from the Dewsbury Road trial site in Leeds, England. PRIMAVERA is concerned with developing and evaluating strategies which integrate Advanced Transport Telematics (ATT) components for queue management, public transport priority, and traffic calming on urban arterial roads. A trial was conducted on a 3km section of the A653, the Dewsbury Road, one of the main radial routes into Leeds, carrying about 23,000 vehicles per day, including many buses. Six queue management strategy components and two bus priority strategy components were investigated for this site. Three of the queue components were incorporated into the SPOT system, five into the SCOOT system, and two into both systems. SPOT-based and SCOOT-based simulation results were obtained, using the NEMIS microsimulation package. Based on the expected changes indicated by the simulations, field trials were designed, to enable the measurement of statistically significant values of changes for a wide variety of effects. Surveys were conducted, and trial results were obtained, for: (1) car and bus flows and speeds; (2) journey times; (3) pedestrian delays; (4) conflicts; and (5) queues.
Abstract: This paper presents the use of a microscopic computer simulation model, SCATSIM, to demonstrate the benefits of SCATS (Sydney Coordinated Adaptive Traffic System) adaptive traffic control under sudden changes of traffic flow conditions during peak flow periods. Quantitative comparisons of traffic control performance under SCATS and fixed-time traffic control techniques show the flexibility of SCATS adaptive control technique and its benefits over fixed-time control in reducing vehicle stops, traffic delays, fuel consumption, and improving air quality.
Abstract: This discussion presents the SAPPORO project which deals with the research and development of a knowledge-based urban road traffic modeling and management system. SAPPORO aims at a homogenous representation of knowledge through the design, modeling, simulation and control process by relying on four basic paradigms: objects, rules, qualitative reasoning, and Actors. The prototype system has been tested using a standard microscopic traffic simulator MISSION. This paper describes the concepts of the prototype system, the graphical user interface, and the accuracy of the qualitative traffic model.
Abstract: Der Tagungsband enthaelt die Beitraege eines Kolloquiums, wobei in 5 Beitraegen jeweils die Produkte/Verfahren und ihre Eigenarten beziehungsweise ihr Leistungsvermoegen von den Herstellern/Entwicklern vorgestellt werden, waehrend in weiteren 5 Beitraegen von Anwendern ueber deren Anforderungen an die Signalsteuerung und die mit den vorgestellen Verfahren gewonnenen Erfahrungen berichtet wird. Auf diese Weise informieren die Beitraege relativ umfassend ueber das Standardsteuerungsverfahren VS-PLUS, das Simulationsmodell VISSIM, mit dem Steuerungsverfahren unter beliebigen verkehrlichen Randbedingungen beurteilt werden koennen, das Software-System TRELAN/TRENDS, mit dem die einzelnen Arbeitsschritte bei der Konzipierung einer Signalanlage rechnergestuetzt interaktiv bewaeltigt werden koennen und das Programmsystem FLUSS, das den Verkehrsingenieur bei Entwurf, Planung, Test und Bewertung von verkehrsabhaengigen Algorithmen unterstuetzt.
Abstract: The singalized intersection chapter of The Highway Capacity (HCM) Manual although widely used, describes a methodology that merely assess the operation at a signalized intersection and assigns a level of service (LOS). The deficiencies and limitations of this chapter can be overcome by using the data from the HCM in conjunction with the TRAF-NETSIM simulation model. This is achieved by using the HCM/CINEMA. This leads to the automation of the procedures for the analysis of signalized intersections using the methodology in the HCM. This article describes a case study, network analysis, the analysis of the results, and the implementation, as well as the results of the mitigation.
Abstract: To alleviate traffic congestion via better traffic flow, the authors propose the use of continuous flow intersections (CFI). The CFI design allows left-turning vehicles to load a left-turn bay that is placed to the left of oncoming traffic and that is accessed by the creation of a midblock, signalized intersection. This article reports on a study to evaluate the effectiveness of the CFI concept using the TRAF-NETSIM microscopic simulation model. Performance of traffic at CFI designs were compared to the performance of traffic at intersections of conventional design. The performance of traffic was quantified by executing the validated TRAF-NETSIM simulation model for both intersection designs over a range of traffic conditions. Results suggest that CFIs offer many advantages; although, the cost of constructing CFIs is two to three times that of conventional intersections. New York City Department of Transportation has evaluated CFIs and is implementing a CFI in the borough of Staten Island. Detailed analysis of the Staten Island model will follow.
Abstract: This project evaluated various intersection control strategies in a simulated environment and also helped establish a live laboratory for use in future testing of new control strategies. The report reviews major intersection control strategies, including the state-of-the-art strategies with adaptive and on-line timing generation features. In addition, it details simulation results for the OPAC control strategy. The NETSIM simulator created the simulation environment for a test network that included part of downtown Minneapolis. Comparison results indicate that OPAC performs best with low-traffic demands, and pretimed control was the most effective during peak periods when traffic demand reached capacity. In conjunction with this project, Minneapolis city traffic engineers installed a machine-vision video detection system at a live intersection laboratory. Located at Franklin and Lyndale Avenues, the test site will help researchers evaluate new control strategies before full-scale implementation in later phases of this research.
Abstract: This project evaluates various intersection control strategies in a simulated environment and also helped establish a live laboratory for use in future testing of new strategies. The report reviews major intersection control strategies with adaptive and on-line timing generation features. In addition, it details simulation result for the OPAC control strategy. The NETSIM simulator created the simulation environment for a test network that included part of downtown Minneapolis. Comparison results indicate that OPAC performs best with low-traffic demands, and pretimed control was the most effective during peak periods when traffic demand reached capacity.
Abstract: An account is given of the use of the HUTSIM simulation model developed to compare and evaluate traffic control systems using a visual representation of traffic conditions. The structure of the model is described and vehicle dynamics considered. The SPOT system for coordinating and optimising signals and handling public transport priorities and the SOS-11 system developed for isolated intersections are described. Using HUTSIM first approximations of delays can be observed with more specific information obtained from output files. Other calculations possible are emissions levels and fuel consumption. The results of comparing an existing traffic control system in Gothenburg with one using SPOT are discussed.
Abstract: The rule-based system CLAIRE was designed to enhance the ability of existing urban traffic control systems to cope with congested situations. This paper reports how a preliminary assessment of this capability was undertaken. It was considered essential for the evaluation environment to be controllable and repeatable. To achieve this, the graphical micro-simulation package AIMSUN was used to model vehicle behaviour through a set of signalised junctions, with simulated detectors providing information to CLAIRE. The model was based on part of the city of Leicester, operating under the SCOOT traffic control system, and it was calibrated using data obtained from on-street surveys. The evaluation environment was in near real-time, and consisted of two interconnected VAX work-stations, with interfacing modules to translate between CLAIRE, AIMSUN and TRANSYT. Five evaluation runs were carried out; two compared CLAIRE's effect with that achieved by re-optimising with TRANSYT, and three compared it with an approximation to SCOOT control. The evaluation showed that CLAIRE could improve upon poor fixed-time plans; whilst improvements with respect to SCOOT were only slight, this is thought to be due to the relatively low level of congestion in Leicester. The paper concludes with recommendations for further trials.
Abstract: Essai D' Emploi De Logiciels Dans L' Analyse De La Circulation Dans Les Rues De Varsovie. Emploi Du "Paquet" Informatique Soap 84, Maxlink, TRAF-NETSIM. Enquete De Donnees. Evaluation De L' Etat Actuel. Optimisation De La Signalisation Sur Les Carrefours Isoles. Coordination De La Signalisation. Comparaison Des Resultats Des Simulations.
Abstract: The HCM/CINEMA computer program is currently used to link the results from analyses using Highway Capacity Methodology with the results from analyses using the TRAF-NETSIM traffic simulation model in various studies conducted by the New York City Department of Transportation. It is described how the program was used in a real case study to evaluate traffic conditions prior to implementing any changes to the local street system. The program has been a valuable tool for the implementation of detour alternatives and also recommending the appropriate modifications in the traffic signal cycle lengths, sequences and splits.
Abstract: A traffic planning feasibility analysis was made of the expected operational characteristics and traffic impacts related to the proposed conversion of a major arterial in downtown Minneapolis, Minnesota, from an existing 1-way to a 2-way arterial. The study evaluated the application and reliability of several computer software programs in the conduct of the feasibility analysis, including TRANPLAN, SIGNAL85, PRETRANSYT, TRANSYT-7F and TRAF-NETSIM. The details of the study are described, and the results are discussed. It is noted that TRAF-NETSIM is useful for modeling very congested, urbanized arterials with high bus volumes, pedestrians, on-street parking and multiple signal locations.
Abstract: Transportation system management (TSM) activities have now been integrated into the overall transportation planning process, and are required as a prerequisite prior to initiating major capacity expansion type of capital works. Although TSM activities are a response to congestion concerns, there is a lack of efficient tools that are capable of estimating delay corresponding to TSM endeavours. All existing delay models are data intensive and require highly specialized human and machine types of resources. In this research, multi-link streets and networks were synthesized and their performance in delay terms was estimated through the use of a microscopic simulation program, NETSIM. The output of NETSIM, in conjunction with physical and traffic characteristics of networks were used to develop the multiple regression type of macro-simulation models of delay. The regrsession models developed are capable of estimating vehicle delay for urban streets. Field data collected by using the video tape technology and maps were utilized to validate the models.
Abstract: The TRAF-NETSIM model is applied to the estimation of the expected traffic impacts associated with a proposed hotel expansion in the urban resort district in Waikiki, Honolulu, Hawaii. The model was used in addition to a traditional analysis based on the Highway Capacity Manual in order to explicitly address persisting concerns raised by the surrounding residential community. Among concerns were the impact of city buses, tour buses unrelated to the proposed project, and tour bus operations serving the hotel complex. The advantages of using an area-wide simulation model to address such concerns when preparing environmental impact statements is illustrated, and the way conditions not directly supportable by TRAF-NETSIM were supported, is described.
Abstract: This is a documentation of work performed in the Puget Sound region in developing a region-wide signal priority treatment. The focus of the effort was to provide priority to buses at signalized intersections by altering the timing at traffic signals to favor such vehicles. That paper describes national experience, local application of signal priority systems, signal priority control strategies, and the results of computer simulation of signalized intersections using TRAF-NETSIM. The cost effectiveness of signal priority treatments is discussed.
Abstract: The main research objective of this study is to improve the limitations of arterial traffic simulation models TRAF-NETSIM and TRANSYT-7F so that they can be used to overcome HOV lane planning deficiencies. For instance, after integrating the improved traffic operation models, the evaluation methods can be more adequate for consideration of complex variables associated with arterial HOV lanes. The traffic impacts of HOV lanes can be analyzed from these improved traffic models; therefore, the relationship between traffic impacts and mode shift behavior can be modeled more accurately. Finally, the guidelines to install a successful HOV lane can be derived according to the results of HOV lane evaluation. In brief, the objectives of this study are to: (1) Modify the logic of TRAF-NETSIM turning movements for simulating arterial HOV lanes realistically; (2) Modify the calculation algorithms of TRAF-NETSIM link statistics to provide the travel time of each vehicle type for HOV lane evaluation; (3) Develop the smoothing factor analytical method for TRANSYT traffic platoon dispersion model so that this model can be enhanced and applied appropriately in mixed-flow and priority lane traffic analysis; and (4) Develop two iteration algorithms for TRANSYT traffic platoon prediction so that this model can simulate congested flow accurately. The scope of this study is limited to focus on the planning process of arterial concurrent flow HOV lanes using traffic simulation models TRAF-NETSIM and TRANSYT-7F.
Abstract: An enhanced delay estimation model for the popular traffic signal optimization model PASSER II-90 is described. Although the results from this model focus on enhancements to PASSER II-90, the findings presented should be useful to the future formulation of the "Highway Capacity Manual" (HCM) methodology for arterial streets. Development of the enhanced delay model primarily involved a four-step arrival rate model instead of the current two-step arrival rate model. Total delay was calculated on the basis of whether the traffic arrivals were early or late. Specifically, delay was estimated using the length and the time of arrival of the traffic platoon at the downstream intersection. TRANSYT-7F was used to investigate the effectiveness of the current PASSER II model and the enhanced PASSER II model. The enhanced PASSER II delay model resulted in large reductions in deviations of the delay values from TRANSYT-7F. Delay-offset trends in enhanced PASSER II-90 now closely follow the TRANSYT-7F delay-offset curves. Delays were also observed to closely follow the NETSIM curves in some regions. It was also observed that in the optimization mode, there was no significant difference in the calculated delay values between the old and the new estimation models. The new delay estimation model in PASSER II-90 also demonstrated that the platoon dispersion modeling in PASSER II compares favorably with TRANSYT's platoon dispersion factor of 0.30 to 0.35. Conclusively, the new model in PASSER II-90 has substantially improved delay estimation over all possible offsets for through traffic.
Abstract: The development and adaption are described of ramp metering strategies for use in signalized networks. The strategies were developed using the micro-simulation model NEMIS. The paper describes the adaptation of the strategies for signalized arterials, producing real time control strategies which can deal with the problems of over-saturation and blocking-back. The strategies will be tested as part of the DRIVE II project PRIMAVERA, which is evaluating integrated strategies involving queue management, public transport priority and traffic calming measures in Leeds, England and Turin, Italy. The addition of strategies to the existing traffic control systems SCOOT and SPOT are discussed, as well as the application of the strategies to over-saturated grid networks.
Abstract: The goal of the work described in this paper is to minimize the total travel time of guided vehicles in a road network. To achieve this, a model based on the "travel time-flow" relationship is developed. Flows can be obtained by using two estimation methods which assume the existence of roadside sensors. The routes are optimized by a static optimisation algorithm. The efficiency of the real time control strategy is tested with a microscopic traffic simulator.
Abstract: A brief description of the SIMNET model is given and the modelling of PROMETHEUS components outlined. The modelling of dynamic route guidance and its application to the central business district of West Berlin are described. The use of data from dynamic route guidance for traffic responsive signal control is examined. The use of congestion time and travel time as parameters were compared. It was found possible to achieve a reduction in delay of 60% of the maximum achievable. The automation of distance control at the approach to traffic signals is then considered. The effectiveness of the system increased with the number of equipped vehicles and needed to be functional for a distance beyond the junction. The possibiity of shortening the green period was also considered.
Abstract: This report deals with the following structures of control: (1) SGDE ("Signal Group Controlled Dynamical"); (2) VOS ("Four Orders Structure"); and (3) "Basic Structure". Until now it has not been determined by investigation which structure has to be applied in which situation in order to come to a traffic flow as favourable as possible. For the three above mentioned structures, traffic situations have been simulated with a different supply of traffic. This has been done by making use of FLEXSYT, a computer program for traffic simulation. The supply differs qua intensity from high-speed traffic on the main direction as well as on the crossing directions, further from slow traffic and public transport. The study is limited to a T junction and a crossing. The comparison between the three structures took place on basis of the criteria loss of time and stops. This study resulted in schemes for slow and high-speed traffic separately in which it has been presented which structure of control seems to be the best, regarding the criteria "average loss of time" and "percentage stops".
Abstract: This research report documents the development models for control of signalized diamond interchanges during oversaturated traffic conditions. Oversaturated traffic conditions occur when the average traffic demand exceeds the capacity of the signal system. The dynamic optimization model proposed is the principal product of this research. The control objective of the dynamic model is to provide maximum system productivity as well as minimum delay for a selected roadway system. A special feature predetermined upper limits. The dynamic model was developed for conventional diamond interchanges and three-level diamond interchanges. The model takes the form of mixed integer linear programming. The effectiveness of the control strategies generated by the dynamic model was compared to those derived from conventional signal timing models, using the TRAF-NETSIM microscopic simulation model. It was found that the dynamic models produced optimal signal timing plans for the oversaturated signalized interchanges. The dynamic model consistently outperformed conventional models with respect to system productivity. This conclusion was drawn from the TRAF-NETSIM simulation. The dynamic model solutions significantly reduced total system delay for most test cases, while slightly increasing the delay for a few test cases.
Abstract: This paper describes an application of the microcomputer version of TRAF-NETSIM, a microscopic interval-scanning traffic simulation model, to determine the expected traffic impacts associated with a proposed hotel expansion in the urban-resort district of Waikiki in Honolulu, Hawaii. The paper illustrates the advantages of using an area-wide simulation versus the traditional HCM techniques. It also describes how certain conditions not directly supportable by TRAF-NETSIM were treated. TRAF-NETSIM is capable of generating graphics files that can be displayed in the form of computer animation. The availability of ANETG, the computer animation routine, greatly enhanced the debugging of the program and the interpretation of the simulation results.
Abstract: A computer program called "The Wizard of Helpful Intersection Control Hints" (WHICH) was developed to satisfy the requirement for an integrated intersection traffic control methodology. The program has been designed to promote future expansion. Three useful features are included: (1) A group of design and analysis programs referred to as the "component programs". Collectively, the component programs offer all of the computations required for intersection control selection. Some are part of the accepted methodology in this field and are already widely used as "stand-alone" programs (e.g., SOAP, SIDRA, HCS, SIGNAL85 and TRAF-NETSIM). Others were developed to fill a specific void. An "executive" program performs the data entry/edit functions and the menu control functions to integrate the component programs. (2) An expert system shell (EXSYS) which provides the inductive capabilities for interpretation of the outputs of some of the component programs. A set of knowledge bases was developed for this purpose. (3) A simple report writer which creates and maintains a text file during the course of the design and analysis process. Selected tables from component program outputs may be added to the report along with brief text passages which describe the tables. These three elements are combined to produce the capability for executing any of the component programs from a common data set, viewing the results, transferring information from one program to another via the WHICH data, and developing a report that documents all of the design and analysis activities. A series of peripheral productivity features are included to make this process as easy as possible for the user.
Abstract: This article presents route guidance strategies for high penetration scenarios. The proposed strategy is conceived for an on-line closed-loop implementation. The basic algorithm is presented first, followed by methods for improving it. These include: a) a method for propagating backward the information on the impedance at a higher speed; and b) the use of a derivative control action. The results of a simulation of the proposed strategy using the NEMIS urban traffic microsimulator are presented and discussed. An architectural solution for implementing the strategy is presented.
Abstract: This report gives a description of traffic metering, especially traffic metering at the border of residential areas. Special attention is paid to traffic metering at the border of a residential area in combination with a reduction of lanes to reduce or even prevent through traffic in order to improve the quality of the environment. For three different sites in the village of Abcoude traffic metering, in combination with a reduction of lanes, is being designed. The principle of traffic metering is translated to a model. Two models have been worked out. The first strategy is based on not letting through any traffic above a specific flow-level until a maximum queue length is reached. In the second strategy the queue length is related to the ratio between the incoming flow and the required flow-level. FLEXSYT is used to simulate the different strategies of traffic metering. Both strategies can be used, but the strategy based on not letting through any traffic above a specific flow-level is preferred, because of a larger application area. On basis of the preferred model an traffic metering design is made.
Abstract: The effectiveness of a left-turn bypass lane on a two-lane rural T-intersection shown by delay data was examined in this research. The bypass lane was a 12-ft-wide marked lane that through traffic may use to move around a vehicle that has stopped to make a left turn onto the minor road of the T. Delay data were generated by the TRAF-NETSIM traffic simulation program sponsored by the FHWA. Delay can be converted into driver cost, which can be compared with the cost of constructing the lane, to provide a good indication of the point at which the extra lane would be warranted. Seven factors that may affect the need for the extra lane were tested: the opposing through volume, the opposing right-turn volume, the through volume, the left-turn volume, vehicle speed, and the distance to the nearest upstream and downstream signal. The presence of a bypass lane was also tested to allow comparison between situations with and without left-turn bypass lanes. Sixty-four simulations were run to test the factors and the interaction among factors. The results indicated that the presence of a bypass lane was a significant factor in delay, especially when higher levels of opposing and left-turn volumes were present. Significant delay and percent stops savings can be realized by including a left-turn bypass lane in certain situations.
Abstract: The purpose of this study was to examine the existing state of the art with regard to the selection of a roadway cross-section for a suburban arterial road. The goal was to develop guidelines to choose between alternative treatments in different situations with respect to land use, traffic volume, travel speed, etc. The primary focus of this research was on arterial highways in developing suburban areas, and two alternative treatments -- nontraversable medians and two-way left-turn lanes (TWLTLs). Several mathematical models were examined, but were found to be not universally applicable. The following investigations were performed to gain additional information: (1) a survey of highway design engineers of different state departments of transportation to identify their experience and preference; (2) an analysis of accidents on Tennessee highways with TWLTLs and medians, respectively; and (3) an analysis of traffic delay on road segments with a TWLTL and a median, respectively, using the simulation model known as NETSIM.
Abstract: A strategy has been defined and is under evaluation, where it is assumed that each intersection of a "guidance network" is equipped with local controllers responsible for computing and distributing route suggestions to individual vehicles. The strategy is characterised by "short term" and "local" adaptations due to both local disturbances and accidents. The assumption is made that a nominal "assignment" of traffic volumes is known to all these controllers in term of flows and percentage of vehicles having destination D to be routed from the ingoing link i to the outgoing link j. Based on the observation of downstream links state variables and their deviation from nominal values as coming from nominal assignment (e.g. system equilibrium assignment) the strategy has been defined so as to adapt the splitting rates at each node to these variations in real-time context. The second part of the paper deals with a first analysis of the results: two different scenarios have been considered with different penetration rates. In the first scenario a medium sized grid network of 117 nodes with a high junction per square km density is modelled. The beacon density is assumed to be high (one per intersection) and the traffic light control is assumed to be fixed time. The average network speed was between 20 and 30 km/hr. In the second scenario the effects of the strategy are assessed in those cases where accidents induce a severe loss of capacity on some links. The accuracy of the results and the indications coming from simulations (by using NEMIS network microsimulator) indicate that the implemented control strategy is really effective.
Abstract: This paper describes the development of a real time control strategy to reduce blocking back during traffic oversaturation periods using the microsimulation model NEMIS. NEMIS is a time increment model capable of tracing the movement of every vehicle step by step, through a network defined by the user. The vehicles are moved along lanes within links according to a car following law, which also holds across a junction. The aim of the control strategy is to reduce the effects of blocking back during oversaturated periods by responding to the traffic conditions and metering the traffic back upstream. The Turin road network was modelled using NEMIS first of all. The network has a main flow towards a critical intersection, and associated blocking back problems. It has 4 lanes on the main links and relatively short links. It does not have large crossflows. Next, the control strategy used in London was programmed into the model and tested on a network with a similar demand profile. The strategy was developed to take account of link lengths, as the links in the Turin network were considerably shorter than the London network, and called the MX strategy. The principle of the MX strategy was to relate the green time on an inbound link to the percentage space left on the next downstream link at the end of red. The first tests of the MX strategy were performed using values of Xc (critical space, or time at which the green time should be reduced) equal to 40% of the link length. Details of the tests and their results are provided.
Abstract: No abstract provided.
Abstract: This report describes work carried out in Turin in collaboration with MIZAR AUTOMAZIONE as part of the DRIVE V1011 CAR-GOES project to develop further the control strategies developed by the author for part of the A41 Finchley Road in London. The aim of the control strategy is to reduce the effects of blocking back during oversaturated periods by responding to traffic conditions and metering the traffic back upstream. Deficiencies in the original TRAFFICQ model are outlined and the use of NEMIS described. A road network in Turin similar to that studied in London which had been modelled using NEMIS was used and the control strategy used in London programmed into it. Initial results showed that blocking back had been reduced but it was necessary to demonstrate the benefits to the system. A series of tests are described which aimed to quantify the efficiency of the control mechanism. Tests were carried out with a critical space of 40% on the downstream link, with varying offsets and either uni- or bi-directional control. Results are discussed and recommendations made for implementing the control strategy and offsets.
Abstract: This report develops a modelling scheme within an urban traffic control (UTC) system so that its performance can be monitored on-line as part of its daily traffic operation. A review is given of the modelling techniques employed for off-line signal optimisation, on-line adaptive traffic control, and on-line performance monitoring. It suggests that a fruitful approach to on-line performance monitoring wou ld be to estimate platoon delays with a TRANSYT-like model within the framework of a control system such as SCATS. The accuracy of TRANSYT was then assessed by validation with floating-car survey data, and by a comparative study with the microscopic model NETSIM. The assessment confirms that TRANSYT modelling techniques would be appropriate for system monitoring. A scheme that makes use of the traffic flow profiles retrievable estimation, and a queue length/delay estimation procedure. This procedure models queue formation and dissipation at a stop line from the predicted arrival profile and the actual stop line departure profiles. The scheme was tested with simulated data, and with SCATS data collected in a field study. Both the queue lengths at the start of a green period, and the maximum back-of-queue that was formed as the head of a platoon joined the stationary queue at a stop line, were recorded. The results confirm the validity of the proposed scheme. The stop line flow profiles were also successfully utilized for automatic incident detection. Lane-by-lane queue length estimation was also found to be feasible. It is recommended that the scheme be employed in a control system for performance monitoring. A scenario of the future of adaptive UTC in the context of dynamic traffic management is also provided.
Abstract: This paper explores the possibility of using vehicle detector data for the purpose of detecting incidents in an urban road network. An Urban Traffic Control (UTC) system, such as SCOOT, which continuously monitors the movement of vehicles over detectors, provides a wealth of information which is yet to be fully exploited. Data obtained from SCOOT installations in Middlesbrough and London are analysed, together with simulated data from the MULTSIM microscopic traffic simulation model.
Abstract: In the evaluation of traffic control by traffic signals the average journey time lost is important. The journey time lost is caused by the slowing down, waiting and accelerating of a vehicle before a bottleneck. Existing methods to measure this lost journey time are often difficult to use and not cheap. In this report a study is presented to develop measuring methods which can fulfill requirements. The working of these measuring methods is discussed and after simulation (by the FLEXSYT program) their reliability is tested. The first method works with a counting detector just before the stop line. Testing on the street shows that the average journey time lost is reproduced in a reliable way. The second method works with the red and green times as input data. This method was not tested on the street but compared with the first method. The second method did not provide reliable figures for journey time lost, but does give an accurate enough impression of it.
Abstract:. The development and testing of a traffic control scheme for the high Density sectors of the Manhattan Central Business District (CBD) is described. the proposed control scheme is based on "spillback avoidance" approach rather Than the conventional "progressive movement" approach. This plan is Characterized by signal splits which reflect the need to service the growing East-West cross street demands in the direction of travel, yet provide near Optimal offsets and splits to the North-South arterial traffic. Under this Scheme, the signal offsets for the cross streets exhibit a "backward Progression" which is optimal (or near optimal) for streets with long queues And slow discharge headways. NETSIM was executed to simulate traffic operations With the existing and proposed signal timing patterns on one of the test Networks. Comparison of the results indicated that the number and duration of Spillback blockages were markedly decreased, with a concommitant reduction in Vehicle travel time and number of stops, coupled with an increase in vehicle Trips serviced. A before-and-after field study yielded similar results, with The new control scheme providing a 20% reduction in overall travel time.
Abstract: The paper presents a new approach to the selection of criteria for the Installation of traffic signals from the point of view of a traffic flow. The Criteria are based on parameters obtained by using the NETSIM simulation Program which enables the testing of all combinations of traffic volumes for a Whole variety of intersection types
Abstract: A mathematical model is described for estimating approach delays at pretimed, signalized, coordinated intersections. The delay models incorporate the size of and flow rate within the progression bandwidth. Platoon dispersion and secondary flows are considered via a simplified platoon-dispersion algorithm calibrated from the TRANSYT-7F model. The basic premise in this study is that traffic is assumed to arrive at the progressed approach in two average flow rates, one within the progression bandwidth, and another outside of it. This modeling concept represents a middle ground between bandwidth models that assume a constant low rate in the dispersed platoon and TRANSYT-like techniques where arrival flow rates vary in each time slice of the cycle length. The delay models are evaluated with Webster's delay formula for random arrivals and with simulated data in NETSIM; in both cases the results compare very favorably. Pending field validation of the delay estimates, an immediate application of the models is the development of progression adjustment factors, which can be readily estimated from system signal-timing parameters and flow rates derived herein.
Abstract: Many traffic control systems on urban arterials and grid networks include signals with actuated controllers. However, commonly used computer programs for signal timing cannot directly optimize the timing of coordinated signals. Users have to apply techniques designed for pretimed signals, and then "translate" the optimized pretimed settings into settings for the actuated controllers. In addition, other signal control choices, such as whether to operate a particular signal as pretimed, semi-actuated, or fully actuated, are left entirely to the user. This report describes the development of procedures for applying the MAXBAND, PASSER and TRANSYT-7F timing programs to systems with actuated controllers. The results from the testing of the procedures on 14 representative grid systems and arterials with the NETSIM simulation model are presented. The report also describes the development and testing of criteria for selecting the type of signal control at specific intersections for commonly occurring field conditions. The report is the first volume produced in this study. Volume 2 is the User's Guide for implementation of the research findings.
Abstract: Many traffic control systems on urban arterials and grid networks include signals with actuated controllers. However, commonly used computer programs for signal timing cannot directly optimize the timing of coordinated signals. Users have to apply techniques designed for pretimed signals, and then "translate" the optimized pretimed settings into settings for the actuated controllers. In addition, other signal control choices, such as whether to operate a particular signal as pretimed, semi-actuated, or fully actuated, are left entirely to the user. This report is a user's guide for applying the MAXBAND, PASSER and TRANSYT-7F timing programs to systems with actuated controllers. Guidelines on how to select the type of signal control at specific intersections for commonly occurring field conditions also are presented. The guidelines are based on operating strategies developed for 14 representative grid systems and arterials and tested through simulation, with the NETSIM program. Chapter 1 of this report describes procedures for translating pretimed timings to actuated controllers' settings for arterial systems. Chapter 2 describes such procedures for grid networks. Criteria for choosing the type of control at selected intersections in coordinated systems are presented in Chapter 3. The report is the second volume produced in this study. Volume 1, the technical report, presents the study methodology, the development of operating strategies, and the results from their application.
Abstract: The primary objective of this study is to acquire an understanding of the current state-of-the-art of traffic signal control strategies at urban street systems. Signalized intersections can be classified into three types: (1) an isolated intersection; (2) an arterial street; and (3) a network. For the analysis of isolated intersection capacity and performance, the commonly used methods include the U.S. Highway Capacity Manual (HCM); Webster's method; and the Australian method. Investigation of traffic signal upgrading strategies in the field can be expensive and time consuming. Unexpected and unnecessary congestion may result and cause negative citizen reaction. Many efforts have been directed towards the development and use of software computer models to evaluate the impacts of various strategies for upgrading traffic signals in different operating environments. The two most widely used packages that were developed to analyze and evaluate traffic operation at isolated intersections are the signal operations analysis package (SOAP) and the traffic experimental and analytical simulation package (TEXAS). For arterial streets, the methods that are commonly used in the timing design of fixed-time arterial systems include conventional methods, the maximal bandwidth method, and the delay/difference of offsets method. The two commonly used packages in the design and evaluation of signal operations at arterials are the progression analysis and signal system evaluation routine (PASSER II(80)) and the arterial analysis package (AAP). For a network that is comprised of a number of signalized intersections, the coordination of traffic signals along the route is regarded as one of the most efficient ways to improve total system performance by reducing delay, stops, fuel consumption, and vehicle emissions. Cycle length, splits, and offsets need to be evaluated and made optimum to improve total system performance. Since the manual work involved in designing the timing plans for a network is quite cumbersome and at times unmanageable, many efforts have been made to develop and use software packages that can assist traffic engineers in solving traffic and transportation management problems on grid networks. The two most widely used packages are TRANSYT and NETSIM. In response to the need to develop advanced operational control programs which would result in a marked improvement in traffic flow, extensive research and develop efforts have been directed towards traffic-responsive control strategies of urban street systems. This area represents one of the leading edges of the traffic control field. The methods that showed good promise to reach the desired goal are: the urban traffic control systems (UTCS); the splits, cycle and offset optimization technique (SCOOT); and the Toronto methods. These methods represent new concepts which could enhance the state-of-the-art in online control techniques.
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