Signal Coordination Plans Research Articles

Traffic signal coordination control for arterials with dedicated CAV lanes

Purpose This study aims to make full use of the advantages of connected and autonomous vehicles (CAVs) and dedicated CAV lanes to ensure all CAVs can pass intersections without stopping. Design/methodology/approach The authors developed a signal coordination model for arteries with dedicated CAV lanes by using mixed integer linear programming. CAV non-stop constraints are proposed to adapt to the characteristics of CAVs. As it is a continuous problem, various situations that CAVs arrive at intersections are analyzed. The rules are discovered to simplify the problem by discretization method. Findings A case study is conducted via SUMO traffic simulation program. The results show that the efficiency of CAVs can be improved significantly both in high-volume scenario and medium-volume scenario with the plan optimized by the model proposed in this paper. At the same time, the progression efficiency of regular vehicles is not affected significantly. It is indicated that full-scale benefits of dedicated CAV lanes can only be achieved with signal coordination plans considering CAV characteristics. Originality/value To the best of the authors’ knowledge, this is the first research that develops a signal coordination model for arteries with dedicated CAV lanes.

Traffic Signal Retiming to Improve Corridor Performance

AbstractTraffic signal retiming involves periodically updating existing signal coordination plans of signalized corridors. Nevertheless, there are still several limitations with the current signal ...

Connected Vehicle-Based Traffic Signal Coordination

Abstract This study presents a connected vehicles (CVs)-based traffic signal optimization framework for a coordinated arterial corridor. The signal optimization and coordination problem are first formulated in a centralized scheme as a mixed-integer nonlinear program (MINLP). The optimal phase durations and offsets are solved together by minimizing fuel consumption and travel time considering an individual vehicle’s trajectories. Due to the complexity of the model, we decompose the problem into two levels: an intersection level to optimize phase durations using dynamic programming (DP), and a corridor level to optimize the offsets of all intersections. In order to solve the two-level model, a prediction-based solution technique is developed. The proposed models are tested using traffic simulation under various scenarios. Compared with the traditional actuated signal timing and coordination plan, the signal timing plans generated by solving the MINLP and the two-level model can reasonably improve the signal control performance. When considering varies vehicle types under high demand levels, the proposed two-level model reduced the total system cost by 3.8% comparing to baseline actuated plan. MINLP reduced the system cost by 5.9%. It also suggested that coordination scheme was beneficial to corridors with relatively high demand levels. For intersections with major and minor street, coordination conducted for major street had little impacts on the vehicles at the minor street.

Feasibility of using a single traffic signal controller to accommodate adjacent intersections

Abstract The operation cost of signalized intersections is usually higher than unsignalized intersections, not only because of the expenses on hardware devices but also due to the device maintenance as well as software upgrading. Moreover, at a signalized corridor, the coordination between signals is also considered to be necessary, which requires additional labor and maintenance costs. With these considerations, this paper aimed to investigate the feasibility of using a single signal controller to control two or multiple adjacent intersections. This study developed a procedure to decide when to use one-controller strategy and evaluated the operation of two real-world cases in Reno, Nevada, where the previous two-controller strategy has just replaced by a one-controller strategy. Based on microsimulation study, it was concluded that the Level-of-Service (LOS), delay, and the average number of stops under one-controller strategy maintained a similar condition in comparison with the previous two-controller strategy, indicating that the proposed one-controller strategy would be a feasible alternative to reduce the operation costs of adjacent intersections. It is expected that reducing the number of signal controllers will not only reduce the infrastructure cost, but also lead to notable operation benefits, such as it facilitates the development of signal coordination plans, and the implementation of future adaptive signal control in a connected vehicle environment, since it reduced the number of communication nodes within the arterial system.

Concurrent Progression of Through and Turning Movements for Arterials Experiencing Heavy Turning Flows and Bay-Length Constraints

Contending with congestion on major urban arterials by providing progression bands has long been a priority task for the traffic community. However, on an arterial experiencing heavy left-turn volumes at major intersections, the left-turn queue may spill back rapidly and further degrade the effectiveness of the through progression band if the left-turn volume and the limited bay length have not been accounted for in the optimization of signal coordination plan. Such negative impact from left-turn queues also justifies the need to take into account the concurrent progression of through and left-turn flows on major arterials. To address these two issues, this paper presents a three-staged signal optimization model that can circumvent or minimize the impact of left-turn spillback to the through movements and concurrently minimize the delay of left-turn flows. The proposed model firstly obtains an initial maximized bandwidth from an existing state-of-the-art method and then maximizes the portion of through bandwidth not impeded by the left-turn overflows. The delay of left-turn flows at each intersection will also be minimized under the obtained effective through bandwidth. The results from the numerical analyses have confirmed the benefits and need of including the left-turn volume and its bay length in the design of dual progression for through and left-turn movements. The simulation experiments further show a reduction in the average delay and the number of stops, by 6.4% and 5.5%, respectively, for vehicles traversing an arterial segment of six intersections, compared with the state-of-the-art model, MULTIBAND.

Signal coordination models for long arterials and grid networks

This paper proposes two models to tackle traffic signal coordination problems for long arterials and grid networks. Both models, denoted as MaxBandLA and MaxBandGN, are built based on Little’s bandwidth maximization model, and the resulting formulations are both small-sized mixed-integer linear programs. Model MaxBandLA can optimize arterial partition plan and signal coordination plans of all the subsystems simultaneously. Model MaxBandGN directly optimizes the offsets for all the signals in a grid network, and as such, no ’cycle constraints’ need to be constructed. Numerical tests are presented to show that both models have the potential to produce coordination plans that are comparable to signal plans optimized by Synchro.

AM-Band: An Asymmetrical Multi-Band model for arterial traffic signal coordination

MAXBAND and MULTIBAND are two well-recognized methods for arterial signal control. In this paper, an Asymmetrical Multi-BAND (AM-BAND) model is developed by relaxing the symmetrical progression band requirement in MULTIBAND. Such a relaxation allows the AM-BAND model to better utilize the available green times in each direction and to provide additional opportunities for vehicular progression. Similar to MULTIBAND, the proposed AM-BAND model is formulated as a mixed-integer linear program. However, in AM-BAND the green bands in each directional section of the arterials do not have to be symmetrical with respect to the progression line. The performance of the AM-BAND model is evaluated for two arterial network data using the AIMSUN microscopic traffic simulation tool. The optimal signal coordination plans are computed by the IBM CPLEX Optimization Studio and compared with signal timing plans generated by AM-BAND, MULTIBAND, and MAXBAND. Simulation results indicate that the traffic signal coordination plans generated by AM-BAND can provide significant benefits compared to those generated by MAXBAND and MULTIBAND.

Incident Management and Network Performance

This paper describes an investigation into the scope for reducing trip time variability associated with incidents (e.g. accidents), through better incident management. The investigation involved using micro-simulation (S-Paramics) to model incident detection and response in a part of the Auckland (New Zealand) network, which includes a motorway and adjacent parallel arterial roads. The effect of blockages on the motorway or an adjacent arterial road, with and without mitigation (e.g. modifying the SCATS arterial road signal coordination plan, using variable message signing and allowing motorway traffic to use the hard-shoulder), were assessed. It was found that the reductions in the variability of trip times, as a result of implementing mitigation options, were much larger than the reductions in mean trip times.

Effect of Arterial Signal Coordination on Safety

Traffic signals are coordinated to improve traffic mobility, but the impact of coordination, particularly specific coordination solutions, on safety is not well known. Engineers who set coordinated signals can use several tools to improve traffic mobility but have no tool with which to account for safety. A study was done on the impact of arterial signal coordination on the frequency and severity of rear-end and right-angle collisions—the two types of crashes that are both prevalent at signalized intersections and likely affected by signal coordination. Multinomial logit models were developed to estimate crash likelihood in short time intervals on arterial intersection approaches, as well as the severity of crash outcome. The obtained models were used to investigate the safety impact of signal coordination and other road and traffic variables. The following results were determined: (a) signal coordination can significantly affect crash likelihood and severity; the concentration of vehicle arrivals in the second half of a green phase is associated with significantly lower crash likelihood and severity; (b) certain components of the traffic flow are most susceptible to crashes; (c) short distances between intersections and short cycle lengths are associated with a lower risk of crash; and (d) the presence of a right-turn bay is associated with a considerable improvement in safety manifested by a lower risk of rear-end and right-angle collisions. The developed models can be used as a tool for evaluating alternative signal coordination plans for safety.

Microscopic Simulation Approach to Effectiveness Analysis of Transit Signal Priority for Bus Rapid Transit

Transit signal priority (TSP) is one of the critical components of bus rapid transit (BRT) and a key technology in enhancing its operational efficacy. It not only provides priority to the BRT vehicle but also manages the trade-off between the delay of buses at an intersection and the impacts on other traffic. This paper focuses on the design and evaluation of a simulation of signal priority for BRT under mixed traffic flow conditions. Taking the Southern Axis BRT Line 1 in Beijing as a case study, different signal priority strategies, including green extension, red truncation, and special phase insertion, are developed for the signalized intersection along the BRT route. A signal coordination plan is designed for the section composed of four intersections in the BRT system. The study uses the VISSIM microscopic traffic simulation model to analyze the impacts of traffic parameters, especially those of nonmotorized traffic, on the effectiveness of TSP along the corridor. Simulation results indicated that the BRT vehicles would typically benefit from transit priority with travel times savings and delay reduction, as well as greater schedule adherence, and suggest that these benefits may be obtained with little negative impacts to the overall system. The results also indicated that the volume of nonmotorized traffic is one of the most important factors that influence the effectiveness of TSP implementation in a mixed traffic flow.

Optimization for Pedestrian and Vehicular Delay in a Signal Network

The efficiency of an arterial network can be enhanced by optimizing the user costs incurred because of delays and other socioeconomic factors. Until recently, research mostly focused on minimizing vehicular delay to optimize user costs. Currently, no signal coordination tool exists to balance delays to both vehicles and pedestrians. A methodology that uses known techniques and available tools to identify an optimal signal coordination plan is developed. Pedestrian delay patterns are obtained from previous research. Delay data for vehicles are based on the modeling of peak-hour traffic conditions in urbanized areas of a hypothetical city. The signal optimization software Synchro (Version 3.2) was used to investigate the variations in vehicle delay with different signal coordination plans and offsets. The results reveal that the best offsets for vehicles and pedestrians are not necessarily the same. Consequently, a signal coordination plan that would benefit both should consider the total user costs of the ...

Optimization for Pedestrian and Vehicular Delay in a Signal Network

The efficiency of an arterial network can be enhanced by optimizing the user costs incurred because of delays and other socioeconomic factors. Until recently, research mostly focused on minimizing vehicular delay to optimize user costs. Currently, no signal coordination tool exists to balance delays to both vehicles and pedestrians. A methodology that uses known techniques and available tools to identify an optimal signal coordination plan is developed. Pedestrian delay patterns are obtained from previous research. Delay data for vehicles are based on the modeling of peak-hour traffic conditions in urbanized areas of a hypothetical city. The signal optimization software Synchro (Version 3.2) was used to investigate the variations in vehicle delay with different signal coordination plans and offsets. The results reveal that the best offsets for vehicles and pedestrians are not necessarily the same. Consequently, a signal coordination plan that would benefit both should consider the total user costs of the system. The results show that the highest total pedestrian delay can spike up the user costs more than the highest total vehicular delay. The offset that generates the optimal user cost can be different from the best offset for vehicles or pedestrians. Thus, a balance between pedestrian delay and vehicular delay can be achieved to arrive at an optimal signal coordination plan.

Factors Affecting Benefits of Implementing Special Signal Timing Plans for Inclement Weather Conditions

Gridlock along arterial systems in cold climates is often the result of adverse weather conditions, which can render the normal signal coordination plans unsuitable as a result of changes in the traffic flow parameters. The current study aims at understanding the impact of different factors on the magnitude of the operational benefits to be expected from implementing special timing plans for inclement weather. The factors investigated include ( a) the characteristics of the signalized corridor, ( b) the type of the simulation model used in the evaluation, ( c) the level of traffic demand, and ( d) the duration of the inclement weather event. To achieve the study's objective, two signalized arterial corridors are selected as case studies, and several simulation experiments are conducted. The results show that signal retiming during inclement weather can result in significant operational benefits (as high as a 20% reduction in control delay in some cases). The results also show that the benefits appear to be greatest when traffic loads are close to capacity and tend to decrease when the available capacity is exceeded. Finally, a significant increase in the benefits is realized with the increase in the duration of the inclement weather event. In one experiment, retiming the signals resulted in a 36% reduction in control delay for a 2-h snow event as opposed to only 18% for a 1-h event.

Factors Affecting Benefits of Implementing Special Signal Timing Plans for Inclement Weather Conditions

Gridlock along arterial systems in cold climates is often the result of adverse weather conditions, which can render the normal signal coordination plans unsuitable as a result of changes in the traffic flow parameters. The current study aims at understanding the impact of different factors on the magnitude of the operational benefits to be expected from implementing special timing plans for inclement weather. The factors investigated include (a) the characteristics of the signalized corridor, (b) the type of the simulation model used in the evaluation, (c) the level of traffic demand, and (d) the duration of the inclement weather event. To achieve the study's objective, two signalized arterial corridors are selected as case studies, and several simulation experiments are conducted. The results show that signal retiming during inclement weather can result in significant operational benefits (as high as a 20% reduction in control delay in some cases). The results also show that the benefits appear to be gr...

Production and analysis of coordination plans using a geographic information system

The TRANSYT program is one of the most extensively used programs for the production of signal coordination plans. The impediments to the development of signal coordination plans are associated with data collection and data input. GIS offers a natural solution to these problems. This paper presents the SIGTRAF system, which uses GIS-T technology for the production of coordination plans using TRANSYT. This system is able to extract topological information from the GIS-T, thus simplifying the process of coding TRANSYT models. A case study was performed, providing insight on how the GIS-T’s thematic mapping capabilities can be used to visually compare different timing plans.

Signal Coordination Benefits for Pedestrians

The potential benefits of reducing pedestrian delay through signal coordination are examined through field data from 10 intersection approaches. The approaches had cycle lengths ranging from 60 to 90 s, walking lengths from the upstream signals ranging from 87 to 105 m, and varying levels of midblock traffic generation. Significant platooning of pedestrians, due to upstream signals, was found on the approaches. This pedestrian platooning could greatly increase or decrease pedestrian delay at the downstream signals, depending on the signal coordination plan. For low green times, the effect of pedestrian platooning on delay was found to be greater than that generally recognized for the automobile mode. Three techniques are described for determining appropriate signal offsets to benefit pedestrians. The first two techniques use average speed and would benefit pedestrians who have speeds that are equal to or greater than the average speed. The third technique determines the delay to be expected from any offset and can, therefore, be helpful in making trade-offs between pedestrian and vehicular delay.