Design And Optimization Of Direction Signal For Left-turning In Intersection

Most of the Chinese urban road intersections with heavy traffic were controlled by using of traffic signals. Signal intersection, as an important component of the urban road, played a pivotal role. The main problem of traffic jam in signal intersection was the conflict of traffic flow, so how to manage the intersection scientifically, in particular signal intersection, find the existing potential, and improve road safety and traffic capacity has become a work of less investment, quick returns and great significance. Widening inflow junction road, setting the left and right turn lanes, setting parking point, building pedestrian over-bridge and underpasses and other measures could play more significant role in the intersection with a small proportion of vehicles to turn left, but the effect was not significant in the intersection with larger proportion of vehicles to turn left. As a result of the impact of vehicles which turned left, the delays increased and capacity reduced efficiency. Therefore, studying on operation rules of left-turn vehicles in planar intersection, and making different response recording to the actual situation was necessary. Various types of vehicles turning in planar intersection aggravated traffic congestion and traffic delays. Turning traffic not only affects the level of traffic capacity, but also greatly increased the vehicular and pedestrian traffic conflicts with vehicles, causing traffic chaos. The left-turn traffic was the linchpin of problems that impacting traffic operations and increasing the number of traffic conflicts. And if we could eliminate or restrict the left-turn traffic flow, the traffic capacity might be greatly enhanced, and congestion and delays might be reduced. Therefore, how to organize and control left-turn traffic was the core issue of traffic order management.The signal timing is one of traffic control measures which was the most direct and the most effective one. Rational design and optimization of left- turn signal helps to ensure the safety and smooth flow.In this paper, based on a large number of documents, a comprehensive analysis of the domestic and overseas traffic flow characteristics and intersection signal timing study were conducted. According to actual traffic survey data, arrival characteristics of motor vehicles flow in intersection was analyzed, and the interaction between left-turn and other traffic laws was studied. At last the left-turn signal was designed and optimized by simulation. The main research and results included as the following:1. Make a summary of the domestic and overseas study, and identify the starting point.Based on checking a large number of literatures, a comprehensive analysis of the domestic and overseas traffic flow characteristics and intersection signal timing study, especially the left-turn traffic study, were made. 2. In light of the actual research, analyze the left-turn traffic characteristics in signal intersection.Traffic flow characteristics analysis was the basis of relevant research, through practical observation and data research, we concluded that traffic flow in signalized intersection was pulsed, and left-turn vehicle met Poisson distribution through the statistical analysis and hypothesis testing. The three operation modes of left-turn vehicles and its impact of the opposite straight vehicle were deeply analyzed. A survey of left-turn lane and straight lane headway were conducted, and histograms of headway were made based on the survey. the effects on saturation flow rate made by the left-turn vehicle were described by comparing headway data.3. According to left-turn traffic characteristics, give the left-turn signal-setting method, and introduce the widely used methods of signal timing.Based on the left-turn traffic characteristics analysis, the setting conditions and principle of left-turn phase were given, the impact of the left-turn line areas, diversion areas and the design of lane were analyzed. At the same time, widely used signal timing methods, including the stop line method, conflict point method, TRRL method and ARRB law, were introduced in order to select the appropriate method when timing signals.4. Select a typical intersection to design and optimist left-turn phase setting and signal timing.Selecting the intersection of Renmin street and Ziyou street in Changchun as study object, a new signal timing programs was made using of Webster method. And evaluation was made using of simulation software VISSIM. The results showed that the left-turn delay and intersection delay were all reduced using the new program.