On Left-turn Traffic Organizations At Signalized Intersections

Left-turn traffic control is one of the most complex problems of the research on signalized intersection in urban road. Thus, this paper studies behavior characteristics of left-turn traffic at signalized intersection, and discusses the qualification and method of install the dedicated signal phase for left-turn, and analyzes its impact on signalized intersection and its capacity.In the beginning, the paper gives out the characteristic and the organization patterns of the left-turn traffic. The left-turn traffic at intersections should be organized properly. If permitted, the intersection traffic capacity can be improved by restricting left-turn and allowing one-way traffic only.Secondly, the paper reviews the theories of signal designing and the capacity at signalized intersections inside and outside the nation, and introduces an approach to developing transitional threshold from permissive to protected left-turn phase at signalized intersection.Thirdly, to analyze the left-turn traffic's impact on the intersection, Chegongzhuang Street and Zhanlanguan Road Intersection is chosen to be observed in the field. The actual vehicle amount passes through the intersection and the signal control datum are collected. Then, the microcosmic traffic simulation software, VISSIM, is used to further validate the impact of install the dedicated signal lights for left-turn traffic at signalized intersection. It designs two simulation cases for the intersection, and chooses the evaluation criterion: travel time, mean delay, queue length. The criteria identify how the dedicated signal lights for left-turn has impact on the intersection's capacity.All in all, under the condition of two phase signal control, with the increase of left-turn traffic, the capacity and efficiency of intersection reduce. To improve the instance, it is important to arrange the left-turn traffic properly.