Research On Signal Control Method For Intersections Under The Oversaturated State

With the development of society and improvement of living standards,car ownership rate is gradually increasing.Due to the construction speed of urban roads is slow,the traffic congestion is becoming more and more serious.Traffic saturation is larger and sustained to increase the traffic pressure.How to effectively implement signal control for city intersections in oversaturated state to improve the traffic efficiency has become an important requirements of the society.In view of the current situation of road congestion,this paper takes into account the defects of existing oversaturated traffic problem researches,and evaluates the traffic states of urban roads based on the analysis of oversaturated traffic phenomena.Combining with the evaluation results,this dissertation has researched in the following areas,including signal control method researches for single intersection,arterial and intersection group in oversaturated state.The specific research contents this dissertation include as follows.Based on the analysis of oversaturated state,traffic phenomena can be given,such as the increasing delay time?vehicle queue accumulation and high green time usage efficiency.Considering the characteristic of vehicle queuing under the oversaturated state,this chapter proposed the evaluation method of oversaturation based on the residual queuing model.In order to quantitatively determine urban road traffic state,the degree of oversaturated state is calculated by introducing two oversaturated severity indexes.The effectiveness of proposed evaluation method is verified through the comparisons evaluation results and the actual traffic states of intersections in the simulation.Considering the single objective control method cannot improve the efficiency,the control strategies for isolated intersection are presented based on the multi-objective control model.Combining multi-objective theory,the control functions are derived with three efficiency evaluation indexes(delay,vehicle queue length,and capacity).Using the weight method that change with traffic flow ratio,these control functions can be integrated smoothly to obtain the multi-objective control model.Considering that random selection of the genetic algorithm operation could lead to the problem of non-optimal values,the modified genetic algorithm is proposed with two-layer selection to add the accuracy of the algorithm.Comparing with the signal control effect under fixed-timing,original genetic algorithm and modified algorithm,it is obviously verified that proposed control method can effectively improve control efficiency of isolated intersection.Most existing coordination control models always neglect the queue discharging time in the calculation process of offset,residual queue calculation model is designed to calculate the queue discharging time.Then the two-direction arterial coordination control model with the improved offset can be presented.In addition to discharge the residual queue under real-time disturbances,an adaptive adjustable parameter method is innovatively designed to adjust green time and optimize the phase sequences in the arterial coordination control.The actual arterial model is constructed by the software VISSIM and the effectiveness of proposed control model and method are verified in the simulation experiments.To improve the overall control effect of road network,the chapter proposes a control strategy for the intersection group based on the improved relevance model.For intersection group,an improved relevance model is presented with two influence factors(residual queue and phase sequence)considered on the basis of Whitson model.Combining with the relevance results,the hierarchical clustering method is applied to intersection group sub-area division.In the process of signal timing,capacity and residual queue ratio are chosen as control objectives.NSGA-? algorithm is adopt to solve the control function for the whole intersection group.In the simulation,the comparisons between there kinds of control effect under no sub-area division?Whitson model and improved model are shown and the effectiveness of control method can be verified.The paper uses the evaluation method of oversaturation to identify the traffic states of urban roads.The signal control for single intersection,arterial and intersection group in oversaturated state is implemented to ease road congestion.In the meantime,the experimental date are collected from real intersection system to improve the effectiveness and the applicability of control strategies in this article.