Research On The Basis Of Setting Left-turn-only Phases Based On Trffic Conflict Theory

The results of sampling statistics show that in 2022,the proportion of traffic accidents occurring at intersections in urban traffic accidents in China reached as high as 30%.Intersections have always been the hardest hit areas for urban traffic accidents,due to the large flow of motor vehicles at intersections,unreasonable phase design,and other reasons that cause traffic conflicts when motor vehicles pass through intersections.Especially at two phase signal controlled intersections,due to the absence of a dedicated left turn phase,traffic conflicts between left turn and opposing straight motor vehicles have become the main factor affecting the overall delay and safety of motor vehicle traffic at the intersection.Therefore,it is necessary to study the conflict between left turn and opposing motor vehicles at two phase signal intersections,and based on this,propose a more suitable left turn dedicated phase setting basis for modern urban two phase signal controlled intersections,which has significant theoretical significance for optimizing intersection signal timing schemes.First,the paper analyzes and summarizes the traffic conflict theory and the research status of left turn dedicated phase at home and abroad,and takes the left turn dedicated phase at two-phase intersections as the research object to determine the main research content of the paper.Secondly,the concept of signal phase is elaborated,as well as the discrimination and influencing factors of the number of conflicts between left turn and opposing straight motor vehicles at two phase intersections.A typical two phase signal controlled intersection in Changchun City is selected for traffic investigation.Based on actual survey data,a model for the number of conflicts between left turn and opposing straight motor vehicles at two phase signal controlled intersections is established.Compared with the actual number of conflicts,the error is less than 10%,which meets the accuracy requirements.At the same time,considering signal control delay and conflict additional delay,a comprehensive delay model was established.Through practical verification,the error was below 5%,proving the reliability of the model.Once again,based on the comprehensive delay model,calculate the average delay of vehicles at two phase and four phase signal controlled intersections,establish a quantitative relationship between delay and conflict number,and then determine the conflict number interval for setting left turn dedicated phases.Through actual data analysis,the results indicate that the conflict number range for setting a dedicated left turn phase is 20-25 times per cycle.Finally,select the left turn traffic volume as the basis for setting the left turn dedicated phase,and compare and analyze it with the number of conflicts.Using VISSIM simulation software and based on actual data,simulate the delay situation of motor vehicles before and after setting the dedicated left turn phase.The results show that the delay increases by nearly 50% after setting the dedicated left turn phase.And this intersection does not need to set a left turn dedicated phase based on the number of conflicts,indicating that using the number of conflicts as the basis for setting a left turn dedicated phase is more conducive to controlling the intersection with two phase signals.