Delay-based Offset Optimization Method For Signalized Intersections

With the increase of urban traffic volume and road network density,the correlation between intersections plays a significant role in traffic signal control.Optimizing the offset between adjacent intersections to improve the efficiency of coordinated control has become an urgent issue for urban traffic control.In order to make up for the shortage of the historical literature on offset optimization,a series of research and discussion on offset optimization with delay as a PI(Performance Index)was conducted,by establishing a coordinated control delay model considering the offset,analyzing the impact of several factors on the optimal offset through simulation,and providing offset optimization algorithms for coordinated control in special traffic scenarios.The main work of this dissertation is summarized as follows:(1)Based on delay diagram,an average vehicle delay model under coordinated control is established.The independent variable of the model is offset.By analyzing the traffic characteristics under different traffic conditions,and by comparing different arrival patterns under isolated signal control and coordinated control,the functional relationship between average vehicle delay and offset is obtained.Based on this functional relationship,and with the minimum average vehicle delay as the control target,offset optimization algorithms for both one-way coordinated control and two-way coordinated control are proposed.The feasibility of the algorithm is verified through numerical and simulation examples.The results of the examples show that the offset optimization algorithms proposed in this dissertation can effectively reduce average vehicle delay.(2)Based on simulation tests,the impact of factors,including initial queuing,traffic demand,and road length on the optimal offset value and on the PI of coordinated control was qualitatively and quantitatively explored.Also,the conditions for the failure of coordinated control are qualitatively analyzed.Utilizing a large amount of simulation sampling data,the correlation analysis and significance analysis are performed between influencing factors and the optimal offset value.Through multivariate polynomial regression,a formula of optimal offset with respect to influencing factors is established.(3)The offset optimization algorithm is expanded in three special traffic scenarios.Firstly,using the traffic wave model and considering the limitation of maximum queue length,a one-way offset optimization algorithm for short links is proposed.Then,according to the difference between the phase sequence settings of symmetric release and asymmetric release,the relationship between the two-way offsets under asymmetric release is derived.Then,an offset optimization method for two-way coordination under asymmetric release is proposed.Finally,a simulation example illustrates the applicability of the two-way offset optimization algorithm when the traffic demands of the two ways do not match each other.