Abstract: In this paper, the modeling and control design for the link-layer intelligent transport system control is presented. Link-layer control systems address the traffic coordination problem on a stretch of highway, and serve as the intermediate link between traditional Advanced Traffic Management Systems (ATMS) and Advanced Vehicle Control Systems (AVCS). A receding horizon optimal control algorithm is presented in this paper. The control algorithm is verified on a microscopic model which keeps track of the motions of each individual vehicle. Simulation results under three perturbed conditions are presented.
Abstract: In this work, the merits of freeway mainline metering as a means of better managing freeway traffic congestion are explored. Freeway mainline metering involves controlling the amount of traffic entering a freeway segment to provide improved travel downstream of the control area. To date, mainline metering has not been applied to a typical urban freeway system, although the concept has been applied successfully to bridges and tunnels. Experiences at these bridges and tunnels indicate that in the presence of a bottleneck, regulating the number of vehicles through the bottleneck will result in improved freeway operations. This study investigates whether regulating mainline vehicle movements can also improve freeway operations without the presence of a bottleneck. Also addressed in this work is whether mainline metering can provide additional benefits over and above typical ramp metering. To evaluate the above hypotheses, the INTRAS simulation model was used to replicate freeway traffic operations. The mainline metering evaluation was based on a variety of mainline volume and on-ramp control conditions. The results indicate that mainline metering can improve freeway operations downstream of the mainline meter. Most importantly, this can be accomplished without increasing the overall delay for vehicles originating upstream of the metering location. In addition, vehicles accessing the freeway from metered on-ramps downstream of the mainline meter are no longer entering a congested freeway mainline, thus reducing overall travel time. These findings appear to indicate that mainline metering is an appropriate freeway management tool.
Abstract: The purpose of this project was to calibrate a freeway simulation model to emulate traffic operating conditions on the Borman Expressway in Northwest Indiana. To replicate Borman operating conditions, the project adopted Integrated Traffic Simulation (INTRAS), a microscopic, stochastic freeway simulation model. Appropriate input data were developed on geometric, traffic and driver behavior information, based on physical measurements and other available data. The model was calibrated and statistical analysis was conducted to validate the accuracy of the results.
Abstract: The purpose of this study was to evaluate the suitability of the TRAF family freeway simulation model FRESIM (Version 4.5) (1) for a simple freeway lane closure by comparing simulated behavior to the observed behavior of a study site. No published studies exist that have validated the use of FRESIM for work zone simulation applications. The study site was a two-lane southbound Interstate 95 (I-95) segment in Cumberland County, North Carolina. The contractor was conducting a four-mile long asphalt milling and paving operation during the evaluation. FRESIM is attractive for work zone modeling due to advanced features including freeway incidents with lane blockage (recommended by the user manual for work zone simulation), lane additions and lane drops, and detector simulation (FRESIM's point processing features) FRESIM does not model reduced lane widths, physical lane tapers, or time of day (night versus daylight conditions).
Abstract: Freeway incident management has become an important issue in departments of transportation nationwide. With many of the nation's roadways operating very close to capacity under the best of conditions, the need to reduce the impact of incident-related congestion has become critical. One way to achieve this reduction is to improve the management of traffic after an incident has occurred, including the use of traffic diversion strategies. Very often, however, diversion strategies are employed without proper consideration given to the effect of such a strategy on the alternate route, which in many cases is congested prior to the addition of diverted traffic. Careful analysis of diversion strategies, which includes examinations of the operational characteristics of both the freeway and alternate routes, can lead to much more efficient and effective strategies. This project establishes a methodology for analyzing diversion strategies using CORSIM, a microscopic simulation model developed by the Federal Highway Administration capable of simultaneously analyzing freeway and arterial roadways. The model process for incident specification and simulation was tested and applied to several case studies. The results of the study show that the model is a valuable tool in analyzing diversion strategies; the critical freeway volume at which diversion becomes advantageous can be determined, as can bottleneck locations on the alternate routes. Signal timing adjustments can be tested and fine-tuned to achieve the ideal maximum flow along the diversion route.
Abstract: This paper describes the project for evaluating strategies for coordinated ramp-metering to be carried out on part of the A10 ring road around Amsterdam. In particular the simulation studies, design of the communications network and the assessment study are considered. The project forms part of the DRIVE II project, EUROCOR. The findings of simulation studies using SATURN and FLEXSYT are briefly outlined. The requirements of the communications network and its development are discussed. The assessment study will focus on the impacts of ramp-metering in general and the impact of different ramp-metering control strategies. The ramp-metering strategies, different situations and effects to be assessed are outlined.
Abstract: No abstract provided.
Abstract: This paper concerns evaluation of the system operating strategies developed for the coordinated operation of ramp metering and adjacent traffic signal systems, in order to improve the operational performance of corridors consisting of freeways, parallel arterials, and perpendicular arterials within a given area. For an integration system capable of interfacing with both freeway ramp control and arterial traffic signal control systems, four operating strategies and several control tactics were identified to be used as integration system functions. Using the INTRAS simulation model and real-world data from a potential selected site, computer simulations were performed to investigate the benefits of developed strategies. Simulation results revealed that various levels of coordination between the ramp metering system and the traffic signal system would improve traffic performance of the corridor.
Abstract: An integrated optimal control model has been formulated to address the dynamic freeway diversion control process. An effective and efficient approach is developed for simultaneously solving diversion control measures, including on-ramp metering rates, off-ramp diversion rates, and green/Cycle ratios for traffic signals on a real-time basis. By approximating the flow-density relation with a two segment linear function, the nonlinear optimal control problem can be simplified into a set of piecewise linear programming models and solved with the proposed successive linear programming algorithm. Consequently, an effective on-line feedback approach has been developed for integrated real-time corridor control. Preliminary simulation results with INTRAS for a sample network have demonstrated the merits of the proposed model and algorithm.
Abstract: The long term traffic and transport policy of the Netherlands has been laid down in the Second Transport Structure Plan (SVV-II). In this plan a new policy theme has been introduced: Traffic control, which purpose is to guarantee optimal use of the existing infrastructure. A set of potential so called "utilisation measures" has been drawn up, but there is hardly any insight in the effectiveness of some of the measures. A study has been done on the effectiveness of two utilisation measures with the help of the microscopic simulation model called FOSIM (Freeway Operations SIMualation). The two utilisation measures are: (1) prohibition for trucks to overtakeon motorways; and (2) exclusion of trucks during congestion on motorways.The main conclusions based on the simulation with FOSIM can be summarizedas follows: The prohibition for trucks to overtake has hardly any effect on the free-flow capacity, and the exclusion of trucks during congestion has a substantial positive effect on the queue discharge capacity (expressed in veh/hr).
Abstract: The level of service on a freeway network is determined by traffic flow on freeway sections with low capacity. These bottlenecks usually consist of sections in which there is some form of discontinuity such as a ramp, a weaving section or a lane drop. For estimation of the capacity near a discontinuity, engineers in the Netherlands use guidelines for freeway design that are in large part based on the Highway Capacity Manual. In most cases the capacity predicted by the HCM is different from empirical data collected on several sites on the freeway network in the Netherlands. At the Transportation Research Laboratory (TRL) of the faculty of Civil Engineering at Delft University of Technology, a study has been done on the traffic operation near discontinuities. In this paper, three types of discontinuities will be discussed: two types of weaving sections (2+1 and 3+1 lanes) and a single lane on-ramp on a 6-lane freeway. To evaluate the capacity, a microscopic simulation model called FOSIM has been used.
Abstract: The high probability that Intelligent Cruise Control (ICC) affects traffic flow by intervening in the driving process motivated traffic research. The latest study involved the actual ICC controller software in the traffic flow simulator AS (Autobahn Simulator). Traffic was simulated for four actual sections of the German motorway (Autobahn) network, each of them with three traffic volumes. The variation of the rate of equipped vehicles gave the effects of ICC. The results of traffic and system evaluation showed increased comfort and safety for equipped vehicles while overall traffic flow was hardly affected at least for less than or equal to 10% equipped vehicles.
Abstract: This paper outlines the simulation and evaluation of the PROMETHEUS system "Intelligent Cruise Control" (ICC). The system has been assessed in terms of traffic safety, transport efficiency and environmental pollution, based on microscopic traffic simulations. The assessment results show considerable safety benefits, whereas the decrease in transport efficiency is negligible.
Abstract: Determination of the achievable capacity of an intelligent vehicle highway system (IVHS) was undertaken. The IVHS architecture proposed by earlier researchers in which vehicles coordinate their behavior to form short-headway platoons on an automated lane was examined. Although many estimates of potential capacity of such an IVHS have been derived, they assume that steady-state flow already has been reached. In such an IVHS, entrance and egress of vehicles are the primary causes of traffic stream disturbance, ultimately dictating the flow rates that can be sustained reliably. Therefore the focus of the investigation was on entrance and egress strategies. A detailed simulator, SmartPath, models the passage of individual intelligent vehicles along the highway and was used to examine transient behavior of the traffic stream under various conditions. Three different strategies were examined for allowing vehicles to enter and leave automated lanes and measuring the corresponding maximum flow rates that are attained. The length of time it takes vehicles to enter an automated lane and therefore to build up high flows was also measured. Finally the effects on flow of vehicles leaving an automated lane were measured, thus indicating that this would be the major source of traffic stream disturbance. It was concluded that, although maximum theoretical capacity cannot be attained, through prudent design of entrance and egress strategies, extremely high throughput can be sustained.
Abstract: Recurrent congestion on the UK motorway network can be a major cause of delay. One approach to eliminating or reducing the effects of congestion which has proved successful, both in the UK and abroad, is ramp metering. This uses traffic signals on entry slip roads to regulate the flow of traffic joining the main carriageway, with the aim of reducing disturbance to the mainstream traffic. There is a range of different approaches to ramp metering, including standard fixed time signals, traffic responsive schemes and coordinated systems, in which the signals on a number of adjacent merges are linked. This study details a comparative study of several different strategies using SISTM (Simulation of Strategies for Traffic on Motorways), a microscopic motorway simulation program which was developed at TRL. The results from this study suggest that, under certain high flow conditions, traffic responsive ramp metering could have some effect in reducing congestion. However, under other conditions, implementation of ramp metering might result overall in increased delays to traffic. When coordinated ramp metering was investigated, no discernable benefits emerged.
Abstract: Describes an area-oriented simulation model used in a loop-detector data collection system. In this simulation model, a "two-time-point measurement model" incorporated with a "back calculation processor" has been developed, in which vehicle length, detector length and lane changing on the detector were taken into consideration.
Abstract: A comparative study was made between the computer simulation programs Freq10 and Flexsyt-I concerning the simulation of "Lanes for Specific Target Groups" (SDG lanes). The reason for this study was an investigation conducted into utilization measures on the motorway between the cities of Gouda and The Hague (situated in the western part of the Netherlands). It was found that the simulation of a SDG lane using Freq10 caused some problems. The question to be answered is whether the program Flexsyt-I will provide a valuable alternative. In order to give an answer to this question, both computer programs are judged on their possibilities regarding the simulation of the traffic operation on motorways. Both programs are considered to be useful for this. In comparing both programs, three models were set up: the basic model with only an access and exit road, the second model with an access and exit road and a SDG lane on the right side of the motorway, and the third model with an access and exit road and a SDG lane on the left side of the motorway. The results are as follows: (1) Using Freq10 and Flexsyt-I, the simulations for the basic model appear to correspondent reasonably well to each other; (2) The simulations for the second model can only be done by making use of the program Flexsyt-I, because it is not possible to use Freq10 to model a SDG lane on the right side of the motorway; (3) Great similarities are found in the results of the simulations for the third model. It appears from this that there is no difference between the traffic operation on a SDG lane located on the left side and on the right side, in case of a low intensity/capacity ratio. The traffic operation on the SDG lane on the left side will become worse than such a lane on the right side, when the intensity/capacity ratios are higher. It is concluded that the simulation of the traffic operation on motorways using FLEXSYT-I is quite possible.
Abstract: No abstract provided.
Abstract: Two popular arterial highway cross-section designs--two-way left-turn lanes (TWLTLs) and nontraversable medians (NTMs, raised or depressed) on four-lane roads--are compared for operational efficiency under identical traffic and development situations. Two broad measures of operational effectiveness, delay and fuel consumption, are obtained through simulation performed using the TRAF-NETSIM model. A three-way factorial design is used to compare and contrast the variables of interest. The results suggest that driveway density, traffic volume on the arterial, and type of design (TWLTL or NTM) have a significant effect on the performance measures such as total delay, fuel consumption, and delay to left-turning traffic and through traffic on the arterial. At low driveway density and low traffic volume, the difference in total delay between the two designs is not found to be significant. At higher driveway densities, no significant difference in delay to left-turning traffic on the arterial can be expected between TWLTL and NTM. However, TWLTL design is found to cause less delay to through traffic and be more fuel efficient at all levels of driveway density and traffic volume.
Abstract: The effect of various levels of ramp metering on traffic flow in a 7-mi-long urban corridor consisting of a freeway, two parallel surface arterials, and seven perpendicular connecting surface arterials was evaluated. The study was conducted both with and without traffic diversion from on-ramps to surface streets using the INTRAS freeway corridor simulation model. Three levels of ramp metering were analyzed to determine how much each would reduce the effects on traffic of an incident on the freeway. For each level of metering, several traffic diversion schemes were introduced in an incremental manner. The diversion of vehicles was implemented for each level of ramp metering until the remaining number of vehicles behind the meters was the same for each level and was less than the storage capacity of the ramp behind the meter. The main conclusion is that, whereas ramp metering improves the traffic flow on the freeway, it adversely affects the total system because of the overflow queues behind the meters, which spill back onto the surface streets. The only metering level that does not do this (in the absence of diversion) is one in which the metering rates are adjusted so that the overflow queues do not occur (equivalent to a queue detector at the upstream end of a ramp overriding the meter when a queue is detected). This level of metering, however, is rarely sufficient to overcome the capacity reduction resulting from an incident. To minimize the adverse effects of ramp metering, an appropriate traffic diversion plan for the implemented ramp metering strategy is required. The impacts on the total system under the optimum ramp metering and the best diversion plan consist of only a 4.1% increase in speed and a 10.5% decrease in delay.
Abstract: This final report describes the key findings of a Washington State Department of Transportation (WSDOT) and Federal Highway Administration (FHWA) project. The research was undertaken during the 1988-1989 time period using mainframe computer versions of the programs. Using Corridor Flow (CORFLO), the investigators modeled the traffic impacts on local and regional roadways that would be caused by the reconstruction of I-405 through the City of Renton, Washington, which is in the Seattle metropolitan area. Using Freeway Simulation (FRESIM), the investigators also modeled I-405 on the northeast side of Renton, where the high occupancy vehicle (HOV) lane, when completed, will transition from the inside to the outside of the freeway (across general purpose traffic). Traffic volume data, traffic signal parameters, and roadway geometric data were obtained and used as needed in each of the computer traffic modeling programs. The CORFLO model could not be adequately calibrated to represent existing traffic flow. The researchers could not determine whether the difficulties in calibrating the model were related to weaknesses in the model itself or to weaknesses in the input data. Use of the CORFLO mainframe computer programs for construction traffic simulation by WSDOT is not recommended at this time. The program requires extensive, detailed data, which is usually unavailable and too costly to acquire given the resources normally available for this type of project. Modifying the CORFLO program to run on personal computers is suggested, and was released by McTrans in September 1992. While the FRESIM model appeared to be able to handle the proposed HOV lane crossover, this could not be verified because the FRESIM output was so complex that it was unreadable. A graphic display of the FRESIM output as a supplement to the existing tabular output is recommended.
Abstract: A general description is given of traffic metering at entrance ramps of motorways and at the border of residential areas. Special attention is paid to traffic metering at the border of a residential area in combination 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. Flexsyt is used to simulate different kinds of strategies of traffic metering. The results are used to determine the design and the restrictions.
Abstract: The efficiency of five alternatives for an intersection between four-lane arterials was investigated through use of a factorial experiment with the TRAF-NETSIM traffic simulation model. A jughandle intersection, three types of median U-turn intersections, and a standard intersection with dual left turn lanes and protected left turn signals were modelled for a range of relatively high to relatively low left turn and through volumes of traffic. The measures of effectiveness (MOEs) investigated included vehicle miles travelled, travel times, and stops per vehicle. Based on current practice in states using jughandles and median U-turns and on the sparse prior literature, the jughandle and median U-turn intersections were expected to reduce travel times because fewer signal phases are required. The experiment results generally showed that one of the median U-turn alternatives, the intersection with four median U-turn roads controlled by "STOP" signs, was very promising with the lowest travel times for most volumes tested and the fewest stops for some volumes. However, the other two median U-turn alternatives tested fared poorly for travel time and stops, and all three median caused the most miles driven. The jughandle intersection was usually the second best of the five intersections for any MOE. Finally, the standard intersection always had the lowest miles driven, and had the fewest stops for some volumes. While many questions remain, the limited test conducted in this research showed the promise of the alternatives and should be followed by more extensive testing.
Abstract: An investigation is presented of entrances with a small curve radius and an acceleration length shorter than 200 m, defined as `short entrance lane'. The merging speeds are often low and these entrances can become bottlenecks during the peak hours. The extent of disturbance is investigated at the short entrance Bunnik during the evening peak. After analysis of the data it was necessary to define various merging types. For each merging type a gap acceptance function has been produced. The Freeway Operation SIMulation model 'FOSIM' is calibrated with the analysed data collected at Bunnik. With different freeway volumes and ramp volumes a first attempt has been made to produce a graph, which indicates the free flow area, the transitional area and the congested area.
Abstract: In the Netherlands the American Highway Capacity Manual (HCM) is commonly used for traffic engineering purposes. Because of the differences in traffic legislation and driver behaviour between the Netherlands and the USA, the HCM cannot be used for the design of weaving sections on Dutch freeways. To create a new set of standards for weaving sections, the micro simulation model FOSIM is used. FOSIM is developed in the USA for simulation of traffic flow on multi-lane freeways and is fully revised for use in the Netherlands. The paper presents the results of calibration and validation of FOSIM for weaving sections on Dutch freeways. Moreover, it describes a method of using FOSIM as a tool to create up to date standards for all sorts of freeway sections.
Abstract: Trucks and buses in The Netherlands are often speeding. In case of calamities on a road, this leads to more lethal accidents, than when speed limits are not being exceeded. Application of speed limiters on trucks and buses must lead to a drastic reduction of speeding. In this study the effects of application of speed limiters on freeway traffic flow are analysed. To obtain sufficient data, a number of simulations were done by means of a microscopic computer model, under development at Delft University.
Abstract: Urban interchanges are a means of facilitating traffic movements between arterial streets and freeway ramps. The single point diamond interchange (SPDI) and the conventional diamond interchange are two specific interchange designs. Essentially, both designs can be treated as signalized intersections. Deviation from the standard signalized intersection operation can be attributed to factors such as longer clearance interval, larger turning radii, different phasing schemes, and different signal offsets between adjacent intersections. Available computer software was reviewed to determine its ability to simulate the operation of the urban diamond interchanges. Data collected at two sites in the Phoenix metropolitan area were used. Five programs were chosen: PASSER II-87, PASSER III-88, TRANSYT-7F, TRAF-NETSIM, and TEXAS. An assessment of each program was conducted to determine its ability to simulate both the SPDI and the conventional diamond interchange. It was concluded that the PASSER III-88 and the TEXAS models simulated the SPDI fairly well. All models except the TEXAS model were able to simulate the conventional diamond design.
Abstract: No abstract provided.
Abstract: This research attempted to compare an arterial roadway with a two-way left-turn lane (TWLTL) with one with a non-traversable median (NTM, raised or depressed) with respect to operational efficiency reflected through delay examined by traffic under a variety of traffic and development situations. A three-way factorial design of experiment was developed, and the microscopic NETwork SIMulation software, NETSIM, was used to generate information for the experiment. The expected differences in traffic delay and fuel consumption between TWLTL and NTM were quantified with the help of NETSIM. It was concluded that driveway density, traffic volume on the arterial, and the type of design (TWLTL or NTM) have significant effect on the performance measures such as networkwide delay, fuel consumption, and delay to left-turning traffic and through traffic on the arterial. At low driveway density and low traffic volume, the difference in networkwide delay between the two designs is not found to be significant. At higher driveway densities no significant difference in delay to left-turning traffic on the arterial can be expected between TWLTL and NTM. However, TWLTL design was found to cause less delay to through traffic and be more fuel efficient at all levels of driveway density and traffic volume. The study did not examine the safety aspects of TWLTL and an NTM, which should be considered for complete evaluation. This study developed estimates of the reduction in traffic delay and fuel consumption when a TWLTL is used instead of an NTM. These estimates would be useful for a benefit-cost analysis of alternative design features.
Abstract: This paper presents a methodology for optimizing performance of a traffic system on the basis of simulated observations of its microscopic behavior. The method integrates simulation and optimization submodels for describing traffic flow on urban freeway lane closures. The stochastic nature of traffic is accounted for in determining the true system response to traffic control variables. The simulation submodel has been validated at a series of work sites in the Chicago area expressway system. The optimization submodel optimizes a single objective function subject to a set of linear constraints. Preliminary model applications included the determination of an optimum merging strategy to be adopted by traffic entering the work zone in lanes to be closed for traffic. The model recommendation yielded the lowest average travel time in the work zone and, interestingly, did not incorporate many early merges; the latter is often viewed as a desired merging strategy. In addition, the optimum merging strategy varied with the traffic flow level entering the work zone and with the character of the objective function to be optimized.
Abstract: This paper describes the findings from the application of the INTRAS microscopic simulation model to evaluate the traffic performance at major freeway weaving sections. The work performed is part of an ongoing research project to develop improved weaving analysis procedures that are particularly applicable to California conditions. The INTRAS model was modified to predict the speeds of weaving and nonweaving vehicles and applied on eight major freeway weaving sections for a range of traffic conditions at each site. Good agreement was obtained between the measured and predicted values. Comparisons with speeds estimated from existing analytical procedures indicated that INTRAS predictions are considerably closer to the field measurements. The potential of the model to predict the capacity and level of service at weaving areas was also investigated. The model produced consistent results on the data sets tested, indicating that it may be used in conjunction with field measurements to develop improved methodologies for the design and analysis of freeway weaving sections. Future steps in this direction are discussed.
Abstract:. The purpose of this project was to develop operational guidelines to Measure the efficiency of flow on the freeway through ramp metering, which is One part of Detroit's surveillance control and driver information (SCANDI) System. The study utilizes the integrated traffic simulation (INTRAS) model, which is a microscopic freeway simulation model, to define the optimal strategy For metering flow onto the freeway. Field data including volume, speed, Vehicle mix, and volume/capacity ratio are used to calibrate and validate the INTRAS model. The results of the study indicate there are significant benefits In terms of reduced delay and increased speed on the freeway.