Research On Variable Approach Lane At Signalized Intersection

With the development of social economy and car ownership, traffic congestion has already become a serious problem to deal with, especially for large cities. The distinct functions undertaken by parts of cities due to continuous development result in the unbalanced distribution of traffic flow on the network in both the temporal and spatial dimensions. To adapt to the time-varying traffic at the intersection, the variable lane is proposed, which allows the dynamic change of lane function to make full use of the spatial resource of the intersection. In this paper, a simultaneous optimization model of variable approach lane and signal timing at signalized intersections is developed to reallocate the time-spatial resources in the intersection, and then the operating efficiency and safety of the variable approach lane on the signalized intersection are evaluated as well.Firstly, after the choice of the objective function and constraints, a simultaneous optimization model of variable approach lane and signal timing at signalized intersections was constructed and analyzed under different situations:3-phases signal control or NEMA ring-and-barrier structure signal control with variable lane on one approach, variable lane on two approaches, also the model adjusted for different signal phase structures. Then it was used to solve the exact problem under different intersection conditions, and the impact of variable approach lane on the operational efficiency of the intersection was obtained. Secondly, the paper studied the influence of different intersection parameters on the approach lane, such as saturation ratios, phase structure, etc. and furtherly some practical advices for the application of the variable lane were put forward. In the end, the paper analyzed safety of intersection by traffic conflicts technique and surrogate safety measure, and it compared the safety performance of intersections with the variable approach lane with those without it by using surrogate safety assessment model.Results show that installation of the variable approach lane can effectively reallocate the traffic resources of the intersection from time and spatial dimension. In addition it can also decrease the average delay per vehicle of the whole intersection and enhance the operational efficiency and the level of service of the intersection. Finally, it is proved there is no significantly difference of the safety performance of the intersection when the left-turn volume of the approach is low, but the safety performance is significantly improved when the left-turn volume of the approach increases.