Constrained dynamic control of traffic junctions

Excessive traffic in our urban environments has detrimental effects on our health, economy and standard of living. To mitigate this problem, an adaptive traffic lights signalling scheme is developed and tested in this paper. This scheme is based on a state space representation of traffic dynamics, controlled via a dynamic programme. To minimise implementation costs, only one loop detector is assumed at each link. The comparative advantages of the proposed system over optimal fixed time control are highlighted through an example. Results will demonstrate the flexibility of the system when applied to different junctions. Monte Carlo runs of the developed scheme highlight the consistency and repeatability of these results.peer-reviewe

17-11 Evaluation of Transit Priority Treatments in Tennessee

Many big cities are progressively implementing transit friendly corridors especially in urban areas where traffic may be increasing at an alarming rate. Over the years, Transit Signal Priority (TSP) has proven to be very effective in creating transit friendly corridors with its ability to improve transit vehicle travel time, serviceability and reliability. TSP as part of Transit Oriented Development (TOD) is associated with great benefits to community liveability including less environmental impacts, reduced traffic congestions, fewer vehicular accidents and shorter travel times among others.This research have therefore analysed the impact of TSP on bus travel times, late bus recovery at bus stop level, delay (on mainline and side street) and Level of Service (LOS) at intersection level on selected corridors and intersections in Nashville Tennessee; to solve the problem of transit vehicle delay as a result of high traffic congestion in Nashville metropolitan areas. This study also developed a flow-delay model to predict delay per vehicle for a lane group under interrupted flow conditions and compared some measure of effectiveness (MOE) before and after TSP. Unconditional green extension and red truncation active priority strategies were developed via Vehicle Actuated Programming (VAP) language which was tied to VISSIM signal controller to execute priority for transit vehicles approaching the traffic signal at 75m away from the stop line. The findings from this study indicated that TSP will recover bus lateness at bus stops 25.21% to 43.1% on the average, improve bus travel time by 5.1% to 10%, increase side street delay by 15.9%, and favour other vehicles using the priority approach by 5.8% and 11.6% in travel time and delay reduction respectively. Findings also indicated that TSP may not affect LOS under low to medium traffic condition but LOS may increase under high traffic condition

Store-and-forward based methods for the signal control problem in large-scale congested urban road networks

The problem of designing network-wide traffic signal control strategies for large-scale congested urban road networks is considered. One known and two novel methodologies, all based on the store-and-forward modeling paradigm, are presented and compared. The known methodology is a linear multivariable feedback regulator derived through the formulation of a linear-quadratic optimal control problem. An alternative, novel methodology consists of an open-loop constrained quadratic optimal control problem, whose numerical solution is achieved via quadratic programming. Yet a different formulation leads to an open-loop constrained nonlinear optimal control problem, whose numerical solution is achieved by use of a feasible-direction algorithm. A preliminary simulation-based investigation of the signal control problem for a large-scale urban road network using these methodologies demonstrates the comparative efficiency and real-time feasibility of the developed signal control methods

GRAPHICAL PERFORMANCE MEASURES FOR PRACTITIONERS TO IDENTIFY SPLIT FAILURES

Detector occupancy is commonly used to measure traffic signal performance. Despite improvements in controller computational power, there have been relatively few innovations in occupancy-based performance measures or integration with other data. This thesis introduces and demonstrates the use of graphical performance measures based on detector occupancy ratios to verify potential split failures and other signal timing shortcomings reported to practitioners by the public. The proposed performance measures combine detector occupancy during the green interval, detector occupancy during the first five seconds of the red interval, and phase termination cause (gap out or force off). These are summarized by time of day to indicate whether the phase is undersaturated, nearly saturated, or oversaturated. These graphical performance measures and related quantitative summaries provide a first-level screening and triaging tool for practitioners to assess user concerns regarding whether sufficient green times are being provided to avoid split failures. In addition, they can provide insight about whether a split adjustment would be an appropriate course of action, and they can provide outcome-based feedback to staff after making split adjustments to determine whether operation improved or worsened. This thesis also includes two case studies that demonstrate how the performance measures can be used to identify phases experiencing several oversaturated splits and compare the number of oversaturated splits before and after reallocating green time to mitigate the oversaturation. Oversaturation was reduced at the intersection of US-31 and 126 th St. north of Indianapolis and at the intersection of River Rd. and the US-231 bypass of West Lafayette

Graphical Performance Measures for Practitioners to Triage Split Failure Trouble Calls

Detector occupancy is commonly used to measure traffic signal performance. Despite improvements in controller computational power, there have been relatively few innovations in occupancy-based performance measures or integration with other data. This paper introduces and demonstrates the use of graphical performance measures based on detector occupancy ratios to verify potential split failures and other signal timing shortcomings reported to practitioners by the public. The proposed performance measures combine detector occupancy during the green phase, detector occupancy during the first five seconds of the red phase, and phase termination cause (gap out or force off). These are summarized by time of day to indicate whether the phase is undersaturated, nearly saturated, or oversaturated. These graphical performance measures and related quantitative summaries provide a first-level screening and triaging tool for practitioners to assess user concerns regarding whether sufficient green times are being provided to avoid split failures. They can also provide outcome-based feedback to staff after making split adjustments to determine whether operation improved or worsened. The paper concludes by demonstrating how the information was used to make an operational decision to re-allocate green time that reduced the number of oversaturated cycles on minor movements from 304 to 222 during a Thursday 0900-1500 timing plan and from 240 to 180 during a Friday 0900-1500 timing plan

A Review of Traffic Signal Control.

The aim of this paper is to provide a starting point for the future research within the SERC sponsored project "Gating and Traffic Control: The Application of State Space Control Theory". It will provide an introduction to State Space Control Theory, State Space applications in transportation in general, an in-depth review of congestion control (specifically traffic signal control in congested situations), a review of theoretical works, a review of existing systems and will conclude with recommendations for the research to be undertaken within this project

Handling Traffic for Major Events: Evaluating Traffic Officer Operations

The campus of Clemson University hosts numerous planned special events every year. The largest seasonal events are the home football games played at Clemson Memorial Stadium. These football games attract crowds in excess of 80,000 fans, most of whom arrive by private vehicle. Trying to maneuver traffic for 80,000 people into one venue is a daunting task in itself. However, trying to maneuver it through a local transportation system designed for a campus with approximately 20,000 students and a city that has approximately 12,000 permanent residents can be a nightmare for state and local traffic enforcement officials. One of the major traffic issues that needs to be addressed during home games is oversaturated intersections. Traffic officers typically manage right-of-way at major intersections either entirely or through push button override of traffic signals. The primary goal of the traffic officer is to try move traffic as efficiently as possible so that queues do not back up excessively causing added congestion at upstream intersections. The change of right-of-way is based entirely on the judgment of the officer. Because the queues at some intersections can back up as much as a mile, providing necessary right-of-way to alleviate the queues can cause cycle lengths to be extremely long. Studies have shown that there are diminishing returns on capacity in intersection operations as cycle lengths grow. This research focuses on evaluating how well traffic officers optimize intersection operations in heavily oversaturated conditions. Traffic data, including volumes, queues, and right-of-way times, was collected before and after four football games during the 2014 and 2015 season. The actual count volumes were adjusted to account for queues and input into SYNCHRO along with actual right-of-way timings provided by the traffic officers. The analysis compares the field observed splits and cycle lengths with optimized splits and cycle lengths attained from SYNCHRO which tries to minimize overall delay. Push button-operated signals are also evaluated. A VISSIM model was created for both manual control and optimized control scenarios to find average delays for each approach. Both SYNCHRO and VISSIM were used for the analysis part of this research. The findings of this research are, Officers are using extremely long cycle lengths in severely oversaturated conditions, and this is resulting in increased delays. When intersections are significantly oversaturated, officers tend to misjudge how long vehicles are in a queue, which leads to some approaches receiving significantly more delay than others

Traffic signal control using queueing theory

Traffic signal control has drawn considerable attention in the literatures thanks to its ability to improve the mobility of urban networks. Queueing models are capable of capturing performance or effectiveness of a queueing system. In this report, SOCPs (second order cone program) are proposed based on different queueing models as pre-timed signal control techniques to minimize total travel delay. Stochastic programs are developed in order to handle the uncertainties in the arrival rates. In addition, the superiority of the proposed model over Webster’s model has been validated in a microscopic traffic simulation software named CORSIM.Statistic