Arterial Signal Coordination with Uneven Double Cycling

In arterial coordination, high traffic volume at large intersections often requires a long cycle length to achieve good two-way progression. This long cycle length, however, often causes excessive delay at some minor intersections where the traffic volume is low on cross streets. This research proposed mathematical optimization models to enable uneven double cycling (UDC) in arterial signal coordination to address this issue. The study first developed a basic UDC model to maximize two-way bandwidths and minimize average delay of cross streets at UDC intersection. The concept of nominal red was introduced to describe bandwidth geometry at UDC intersections. Disjunctive programming technique was used to convert a mixed integer nonlinear programming problem into a mixed integer quadratic programming problem for computation efficiency. The study further improved the basic UDC model to consider pedestrian needs and enhanced the modeling through multicriterion optimization. The additional objectives included minimal arterial average delay and minimal arterial number stops at UDC intersections, maximal variable bandwidth, and maximal secondary bandwidth. With all the mathematical models ready, numerical experiments in the study explored factors affecting the applicability of the UDC control scheme. Results of the numerical experiments provided thresholds of parameters for determining UDC applicability. A rule of thumb was that when the green time of an intersection in the peak direction is longer than that at the critical intersection by at least the sum of minimum green time and per phase lost time, UDC control might be beneficial at this intersection. The research then conducted a case study to evaluate the performance of various models on the field data of an arterial with four intersections. Comparing with conventional SC control under fixed timing, the UDC models significantly reduced delay at UDC intersections for both through and left turn movements, and reduced number stops at SC intersections. UDC control under actuated operation overcame the shortcoming of increasing arterial number of stops compared with fixed timing. Finally, the advantages and disadvantages of UDC control were summarized, and preliminary guidelines were provided for UDC implementation. Future study topics were also recommended

SIGNAL SETTINGS SYNCHRONIZATION AND DYNAMIC TRAFFIC MODELLING

The object of the paper is to investigate the effect of signal synchronization on the traffic flow patterns on the network and validate results of synchronization problem in signal setting design. A platoon based traffic model is applied to solve both one-way and two-way synchronization problems in under-saturated conditions. Assessment of results through dynamic traffic assignment model shows that solution found is rather robust and, if more traffic is attracted by the improved arterial performance, larger benefits can be achieved on the whole network. A specific analysis has been conducted to point out the representation of queue propagation and the gridlock phenomenon

A General Maximum Progression Model to Concurrently Synchronize Left-Turn and through Traffic Flows on an Arterial

In the existing bandwidth-based methods, through traffic flows are considered as the coordination objects and offered progression bands accordingly. However, at certain times or nodes in the road network, when the left-turn traffic flows have a higher priority than the through traffic flows, it would be inappropriate to still provide the progression bands to the through traffic flows; the left-turn traffic flows should instead be considered as the coordination objects to potentially achieve better control. Considering this, a general maximum progression model to concurrently synchronize left-turn and through traffic flows is established by using a time-space diagram. The general model can deal with all the patterns of the left-turn phases by introducing two new binary variables into the constraints; that is, these variables allow all the patterns of the left-turn phases to deal with a single formulation. By using the measures of effectiveness (average delay time, average vehicle stops, and average travel time) acquired by a traffic simulation software, VISSIM, the validity of the general model is verified. The results show that, compared with the MULTIBAND, the proposed general model can effectively reduce the delay time, vehicle stops, and travel time and, thus, achieve better traffic control

Robust Optimization Model for Bus Priority under Arterial Progression

The purpose of this study is to design a real-time robust arterial signal control system that gives priority to buses while simultaneously maximizing progression bandwidths and optimizing signal timing plans at each intersection along the arterial. The system architecture is divided into three levels. At the progression control level bandwidths are maximized. Existing progression strategies do not use real-time traffic data or use simple mathematical models to estimate traffic evolution. The proposed model eliminates this drawback by using real-time data to develop a neural network model for predicting traffic flows. Rather than using pre-specified values, queue clearance and minimum green times are computed as functions of the predicted queues. To eliminate uncertainty in the prediction due to the long time horizon, robust discrete optimization technique is used to determine the progression bands. At the intersection control level, signal timing plans are optimized subject to bandwidth constraints to allow for uninterrupted arterial flow, and minimum green constraints for driver safety and to discharge average waiting queues. At the bus priority control level, whenever a bus is detected and is a candidate for priority it is granted priority based on a performance index that is a function of bus schedule delay, automobile and bus passenger delays, and vehicle delays, subject to bandwidth and minimum green constraints. Minimum green constraints ensure that other traffic users are not unduly penalized. Bandwidth constraints allow for uninterrupted arterial flow despite a preferential treatment of buses. The performance of the proposed system is evaluated through a case study conducted in a laboratory environment using CORSIM. Results show that the models developed at the three levels are superior to the signal control implemented in the field, and the alternatives that use the off-line MULTIBAND model for progression for all traffic scenarios. Robust optimization was highly effective in reducing control delays, stop times, queues, and bus delays, and increasing throughput and speeds, when traffic volumes were high. The model that integrated bus priority with robust arterial signal control produced the most reductions in bus delays while not causing significant delays to automobiles

Measuring the Quality of Arterial Traffic Signal Timing – A Trajectory-based Methodology

Evaluating the benefits from traffic signal timing is of increasing interest to transportation policymakers, operators, and the public as integrating performance measurements with agencies’ daily signal timing management has become a top priority. This dissertation presents a trajectory-based methodology for evaluating the quality of arterial signal timing, a critical part of signal operations that promises reduced travel time and fewer vehicle stops along arterials as well as improved travelers’ perception of transportation services. The proposed methodology could significantly contribute to performance-oriented signal timing practices by addressing challenges regarding which performance measures should be selected, how performance measurements can be performed cost-effectively, and how to make performance measures accessible to people with limited knowledge of traffic engineering. A review of the current state of practice and research was conducted first, indicating an urgent research need for developing an arterial-level methodology for signal timing performance assessments as the established techniques are mostly based on by-link or by-movement metrics. The literature review also revealed deficiencies of existing performance measures pertaining to traffic signal timing. Accordingly, travel-run speed and stop characteristics, which can be extracted from vehicle GPS trajectories, were selected to measure the quality of arterial signal timing in this research.Two performance measures were then defined based on speed and stop characteristics: the attainability of ideal progression (AIP) and the attainability of user satisfaction (AUS). In order to determine AIP and AUS, a series of investigations and surveys were conducted to characterize the effects of non-signal-timing-related factors (e.g., arterial congestion level) on average travel speed as well as how stops may affect travelers’ perceived quality of signal timing. AIP was calculated considering the effects of non-signal-timing-related factors, and AUS accounted for the changes in the perceived quality of signal timing due to various stop circumstances.Based upon AIP and AUS, a grade-based performance measurement methodology was developed. The methodology included AIP scoring, AUS scoring, and two scoring adjustments. The two types of scoring adjustments further improved the performance measurement results considering factors such as cross-street delay, pedestrian delays, and arterial geometry. Furthermore, the research outlined the process for implementing the proposed methodology, including the necessary data collection and the preliminary examination of the applicable conditions. Case studies based on real-world signal re-timing projects were presented to demonstrate the effectiveness of the proposed methodology in enhancing agencies’ capabilities of cost-effectively monitoring the quality of arterial signal timing, actively addressing signal timing issues, and reporting the progress and outcomes in a concise and intuitive manner

Arterial Signal Coordination with Uneven Double Cycling

In arterial coordination, high traffic volume at large intersections often requires a long cycle length to achieve good two-way progression. This long cycle length, however, often causes excessive delay at some minor intersections where the traffic volume is low on cross streets. This research proposed mathematical optimization models to enable uneven double cycling (UDC) in arterial signal coordination to address this issue. The study first developed a basic UDC model to maximize two-way bandwidths and minimize average delay of cross streets at UDC intersection. The concept of nominal red was introduced to describe bandwidth geometry at UDC intersections. Disjunctive programming technique was used to convert a mixed integer nonlinear programming problem into a mixed integer quadratic programming problem for computation efficiency. The study further improved the basic UDC model to consider pedestrian needs and enhanced the modeling through multicriterion optimization. The additional objectives included minimal arterial average delay and minimal arterial number stops at UDC intersections, maximal variable bandwidth, and maximal secondary bandwidth. With all the mathematical models ready, numerical experiments in the study explored factors affecting the applicability of the UDC control scheme. Results of the numerical experiments provided thresholds of parameters for determining UDC applicability. A rule of thumb was that when the green time of an intersection in the peak direction is longer than that at the critical intersection by at least the sum of minimum green time and per phase lost time, UDC control might be beneficial at this intersection. The research then conducted a case study to evaluate the performance of various models on the field data of an arterial with four intersections. Comparing with conventional SC control under fixed timing, the UDC models significantly reduced delay at UDC intersections for both through and left turn movements, and reduced number stops at SC intersections. UDC control under actuated operation overcame the shortcoming of increasing arterial number of stops compared with fixed timing. Finally, the advantages and disadvantages of UDC control were summarized, and preliminary guidelines were provided for UDC implementation. Future study topics were also recommended

Investigation of tram movement indicators in general structure of traffic flow

In the work, the average operating speed of the tram is investigated on the sections with the high density of the road network. Such peculiarities are inherent to the cities where its configuration has developed historically, and trams move in the general structure of traffic flow which is predetermined by the absence of traffic capacity reserves in the old, as a rule, central part of the city. It frequently causes the reduction of the whole traffic flow speed of movement, in particular on the intersections and within public transport stops. Determination of the mutual impact of automobile movement and trams is topical because, on the one hand, trams, taking into account their dynamic and technological movement peculiarities, worsen traffic flow indicators, and on the other hand, vast traffic intensity causes downtime of the trams rolling stock in the queues before the intersection that decrease passenger transportation quality. As a result of the research reported in this paper it was managed to determine the amount of change of the average tram operating speed for different methods of traffic flow control for different times of day

Network Wide Signal Control Strategy Base on Connected Vehicle Technology

This dissertation discusses network wide signal control strategies base on connected vehicle technology. Traffic congestion on arterials has become one of the largest threats to economic competitiveness, livability, safety, and long-term environmental sustainability in the United States. In addition, arterials usually experience more blockage than freeways, specifically in terms of intersection congestion. There is no doubt that emerging technologies provide unequaled opportunities to revolutionize “retiming” and mitigate traffic congestion. Connected vehicle technology provides unparalleled safety benefits and holds promise in terms of alleviating both traffic congestion and the environmental impacts of future transportation systems. The objective of this research is to improve the mobility, safety and environmental effects at signalized arterials with connected vehicles. The proposed solution of this dissertation is to formulate traffic signal control models for signalized arterials based on connected vehicle technology. The models optimize offset, split, and cycle length to minimize total queue delay in all directions of coordinated intersections. Then, the models are implemented in a centralized system—including closed-loop systems—first, before expanding the results to distributed systems. The benefits of the models are realized at the infant stage of connected vehicle deployment when the penetration rate of connected vehicles is around 10%. Furthermore, the benefits incentivize the growth of the penetration rate for drivers. In addition, this dissertation contains a performance evaluation in traffic delay, volume throughput, fuel consumption, emission, and safety by providing a case study of coordinated signalized intersections. The case study results show the solution of this dissertation could adapt early deployment of connected vehicle technology and apply to future connected vehicle technology development