Research On Phase Overlap Control Method Of Roundabout

No signal roundabout has good adaptability with low saturation flow of traffic. However, with rapid growth of vehicle ownership in our country, the saturation of domestic traffic flow is increasing. The traffic jam of no signal roundabout is becoming more and more common. The contents proposed in this paper, such as the transformation timing and conditions of no signal roundabout, the adaptability and improvement of existing control methods and putting forward new signal control methods, are important to alleviate the problem of traffic jam.Based on the traffic survey of parts of the roundabouts in Harbin, Changchun and Xiamen, this paper analyzed the conflict characteristics and traffic characteristics of no signal roundabout, and held that the conflict characteristics of no signal roundabout was that passive conflicts had the priority. Besides, on the basis of this analysis, the paper analyzed the traffic characteristics of crossing pedestrian and vehicles in entrance lane and weaving section of no signal roundabout, and provided support to the running evaluation of no signal roundabout.In addition to the analysis of running characteristics, the paper used the capacity of weaving section calculated by the provisional formula of the UK Department of the Environment as the basic indicator of evaluating the running state of no signal roundabout. The VISSIM was applied to simulate the traffic flow characteristics of roundabout. The paper calibrated the linear regression model of maximum vehicle capacity of the entrances of roundabout which has three entrance lanes and three circular vehicle lanes. By simulating the weaving sections of no signal roundabout under different saturation conditions, the paper obtained the evaluation indicators of running state of no signal roundabout and applied the SPSS to make cluster analysis of them. At the same time, combined with the perception of the simulation process, the paper divided the running state of roundabout into four grades, and given the quantitative division indicators.The paper analyzed the control strategies, timing methods and channelization of secondary signal control mode and single control mode of left turn, and two-phase signal control mode of cross roundabout. Combined with the VISSIM simulation analysis of the running characteristics of different signal control methods of roundabout, the paper also analyzed the adaptability of different signal control methods in the perspectives of geometric and traffic conditions.Considering the limitation of applicable conditions of secondary signal control mode, the paper proposed a improved secondary signal control mode, built timing optimization model of the improved secondary signal control mode, and made studies on its applicable conditions and channelization. The roundabout of LIFANWU Garden was taken as a simulation case. The simulation results show the improved secondary signal control mode can effectively improve the operating efficiency of roundabout.In accordance with the limit applicable conditions of existing signal control methods of roundabout, the paper put forward a phase overlap control method of roundabout: each phase for an entrance. The timing optimization model was built and its applicable conditions and channelization were studied. The roundabout of BOWUGUAN was taken as a simulation case. The simulation results show the phase overlap control method can effectively alleviate the traffic congestion and improve the capacity of roundabout.