Signal Control Parameters Research Articles

Integrated Adaptive-Signal Dynamic-Speed Control of Signalized Arterials

This paper demonstrates the feasibility of an advanced concept of traffic control for congested urban arterials in an intelligent transportation system (ITS) setting. The core idea of the new concept is to integrate the capability of dynamic adaptive signals with dynamically optimized time-dependent variable speed. Under such control, speeds would be automatically optimized and set by a central computer in parallel with the other signal control parameters. Speed and signal control parameters would change between links and over time, in response to changing traffic conditions. Drivers would follow the optimized speed as they enter a link. Once an optimal speed has been set for a link, it remains constant until the control cycle ends. Link speeds would be updated only at the end of every control cycle. The control cycle may change in length as system conditions evolve. The new control concept was tested on a congested arterial with multiple links. The arterial system was modeled as a discrete event time var...

Adaptive traffic signal control for the fluctuations of the flow using a genetic algorithm

This paper describes adaptive traflic signal control for the fluctuations of flow using a genetic algorithm (GA). The target of signal control parameters for this study is offset that is difficult to optimize because of its variety of combinations. Offset optimization using GAs has been investigated in previous studies. Most of them however, focused on signal control in a condition where the traf%c flow was fixed. In a practical scene, the rate of flow changes as time passes, so that offset-optimization considering these fluctuations of flow is required. As a case study, an urban traflic route in a city of the Chubu region in Japan, with twenty-one signalized intersections, was tested. To perform offset-optimization by a GA, offset values were represented in a chromosome having the same number of genes as the signals. Two different conditions of traffic flow, slow monotonous and rapid increase, were chosen for the simulation. The results show that the offset optimization technique used in this study was a valuable one for efficient signal control.

Design and evaluation of dynamic traffic management strategies for congested conditions

This paper presents a procedure for dynamic design and evaluation of traffic management strategies in oversaturated conditions. The method combines a dynamic control algorithm and a disutility function. The dynamic algorithm designs signal control parameters to manage formation and dissipation of queues on system links with explicit consideration of current and projected queue lengths and demands. The disutility function measures the relative performance of the dynamic control algorithm based on preset system performance goals. The user may statically select the management strategy, or alternatively the system may be instructed to set off different management schemes based on predefined performance thresholds. The problem was formulated as one of output maximization subject to state, control, and traffic management strategy choices. Solutions were obtained using genetic algorithms. Four traffic management plans were tested to show the capabilities of the new procedure. The results show that the procedure is able to generate suitable signal control schemes that are favorable to attaining the desired traffic management goals. The results showed that multiple, or hybrids of single measures of effectiveness may need to be examined in order to correctly assess system performance. The procedure has potential for real-time implementation in an intelligent transportation system setting.

Optimization of Signal Control Parameters for Two-Way Traffic Arterials

This paper studies a signal control method which controls congestion lengths on two-way traffic arterials systematically. The signal control system of the congestion length is described by a nonlinear time-varying discrete dynamic system and synthesized by using the feedback control. A balance control algorithm in which the three signal control parameters consisting of the cycle length, green split and offset are searched systematically so as to minimize the sum of congestion lengths on the arterial is presented. From the comparison between measurement values and simulation values, it is confirmed that the balance control algorithm works effectively to reduce the congestion lengths on the arterial

Simultaneous Determination of Control Parameters in Traffic Signal Control Systems

The coordinated traffic signal control parameters are characterized by cycle length, split and offset. These parameters should be carefully calibrated so that the total performance index is optimized. Our scope of opitimization is called sun-area, which is defined by a series of intersections. The conventional methods may be deficient in that each parameter is calculated individually and the overall traffic index is not considered. This paper describes a new method of determining coordinated control parameters simultaneously. Since it is difficult to express the delay time as a function of the offset parameter, the procedure is divided into two parts. In the first step, the cycle length and the split are obtained by minimizing the total traffic delay. The optimal offset is calculated so as to maximize the bandwidth, which is the fraction of time during which vehicles may pass through all the intersections without stopping in the sub-area. In the second step, we estimate the total queue length in the sub-area by using a microscopic traffic flow simulator. By integrating these two steps, several control planes are obtained, and the best solution is chosen among them.

Genetic Algorithms for Traffic Signal Control and Queue Management of Oversaturated Two-Way Arterials

The formulation and solution of a dynamic signal control and queue management algorithm for two-way oversaturated arterials are presented. The algorithm is structured to find optimal control and queue management in at least one direction: the primary direction. The other direction is optimized only subject to the fulfillment of the constraints on the primary direction. The main idea of the procedure is to manage queue formation and dissipation through proper design of signal control parameters such that queues are always contained within respective links and that spillbacks are prevented. The two-way control procedure presented accounts for all possible traffic flow regimes that may form as a result of queue management schemes. Genetic algorithms were used to solve the problem. The results show that although the algorithm provides optimal control and queue management in the primary direction, it was also able to manage queues in the secondary direction so that the occurrence of queue spillbacks is prevented. Progression was attainable only in the primary direction. However, the algorithm was able to effectively deal with evolving traffic queues in both directions. In all but one link, traffic was successfully contained in the respective links, thus preventing spillback.

Femtosecond real time probing of reactions XXII Kinetic description of probe absorption fluorescence depletion and mass spectrometry

A theoretical description of femtosecond transition-state dynamics is developed and compared with experimental results, with numerous examples. We focus on the population flow, employing a kinetic model, with the objective of studying the general trends and signal control parameters; we do not include coherence for the sake of acquiring a simplified picture with operational parameters. Different methods of detection are addressed, such as laser-induced fluorescence, depletion, absorption, and mass spectrometry. The response of the molecular system is derived for various types of dynamics with one or more rate determining processes. The significance of the relative time scales associated with the rates is explored and the effect on transients of the ratio of probing cross-sections is examined. Furthermore, the influence on the observed signal of the finite temporal width and shape of the laser pulses is quantified. Effects are discussed both in the unsaturated and saturated regimes of transition probabilities, demonstrating characteristic features of both regimes.

A Simulation Experimental Study of Traffic Signal Control by Using Genetic Algorithm.

In urban street networks, traffic flow is seriously affected by traffic signals. A traffic signal is controlled by using three parameters, cycle, split and offset and these parameters should be determined based on traffic conditions.This paper discusses on the optimal signal control in small street networks. First, we apply genetic algorithm to the optimization of signal control parameters. In this approach, we use the microscopic traffic simulation for calculating fitness value. Secondly, we analyze the optimal signal control in small networks as comparing with the results of conventional approaches and prove effectiveness of our proposed approach. Further, we propose the practical method of setting signal control parameters based on traffic conditions.

Safer signalized junction design and self‐optimizing control

AbstractThe UK Transport Research Laboratory has long had a Worldwide reputation for contributions to the field of traffic signal control, especially as originators of the TRANSYT and SCOOT signal coordination methods. This article describes some less widely known work. Accident risk at urban junctions and on road links between them is related to a wide variety of factors including: traffic and pedestrian flows, signal control parameters, geometry, and other layout features. Comprehensive studies have derived, and are continuing to derive, quantitative risk relationships for use in off‐line software. Those for individual signalized cross‐roads have already been incorporated in the TRL's program OSCADY to assist junction design. Now, an area‐wide safety model incorporating the CONTRAM traffic assignment program is being actively developed to provide a tool for evaluation of network traffic management schemes. For on‐line signal control at individual junctions, the MOVA system has been developed to provide a delay‐minimizing or capacity‐maximizing control logic as appropriate. ‘Before and after’ comparisons with the UK's previous fully vehicle‐actuated signal system are presented, including both delay and safety aspects.

AN EQUILIBRIUM METHOD FOR ESTIMATION OF TRAFFIC MANAGEMENT SCHEMES AND TRAFFIC OPERATION

To introduce traffic management schemes and traffic operation, influences on traffic flows should be estimated precisely. To this end, a traffic simulation model in urban road networks is proposed in this paper. That is an equilibrium traffic assignment model combined with estimation of junction delays. For each turning flows, junction delays are induced analytically as a function of flows and traffic signal control parameters. Traffic assignment uses an iterative procedure, and flow-delay curves are selected based on latest link flows. In this method, precise modeling of junction flows was enabled and simulation process was sharply promotea in etticiency compared with usual simulation model. Through an application to Kobe city, it was cleared that the model is useful for estimation oftraffic management schemes and traffic operation.