Research On The Spacing Of Signalized Intersections Of Urban Arterial Roads

With the development of urban traffic problems, the space optimization of traffic facilities of urban arterial roads gets attention. As an important part of the optimization, reasonable spacing of signalized intersections of arterial roads could help to ease traffic congestion and heighten safety level as well as make advantageous effects on modifying road traffic facilities, managing arterial intersections, saving energy and protecting environment. Currently, single signal control has considerable difficulties to ease city traffic pressure. The popularization and reasonable application of signalized coordination and control system for arteries is the inevitable trend of signalized urban roads. But there is no systematic criterion and research achievement regarding the setting of signalized intersections of urban arteries in our country which leads to the common phenomenons such as high density and random setting of signalized intersections, etc. It not only hinders the coordinating and controlling functions of arteries, but also generates potential safety hazards. The paper tries to bring forward a way to determine the spacing of signalized intersections of arterial roads on the basis of the degree of routes correlation of intersections.To start with, the paper presents theoretical analysis of traffic safety and efficiency of cross signalized intersections of urban arterial roads. It expounds on the safety of the intersections by analyzing traffic flow patterns, driving behavior and vehicular traffic of intersections. The paper continues to expound the traffic efficiency of signalized intersections of urban arterial roads by analyzing the controlling method of traffic signals, controlling parameters and coordinating parameters for operating efficiency.Then according to the analysis of driving behaviors including perception, response, braking and queuing, it puts forward the length model for upstream functional area of signalized intersections. Meanwhile stopping sight distance is selected as the calculating model for the length of downstream functional area. Through the analysis of the lane-changing driving behaviors between the neighboring functional areas of intersections and the studies of safe sight distance, minimum safe spacing calculating model for single signalized intersections is brought forward.After analyzing the implementing conditions of artery coordinating and controlling system, the distribution of traffic flow, the maximal spacing, the saturation state and the signal period, it pointed out the relationship between correlation of intersections and artery-coordinated control. Degree of routes correlation was regarded as the criteria for priority level in artery-coordinated controlling. Loop iteration method is applied in calculating the spacing of intersections.Finally, the paper targets arteries constituted by actual intersections as studying objects and conducts deduction and simulation to the actually-measured data, hence proving the validity of the spacing calculating method mentioned above. It also compares the efficiency in light of travel time and delay, then offers objective evaluation to the models.After simulating the intersections spacing models of arterial roads proposed by the paper, the travel time is reduced and delay decreases with the improvement of spacing. The studies results show that, the logical spacing is helpful in improving the operating efficiency of urban arterial intersections and heightening the rationality of traffic facilities settings. The models prove to have value in popularization and application as well as further research.