The Lane-changing Research And Safe Operation Of The Ramp Exit On Expressway

With the rapid development of the social economy,the expressway has been an important role of in China’s transportation network and become increasingly prominent in passenger and freight transportation.Since the traffic demand increase quickly in the current society,the traffic problems on the expressway have attracted the attentions of many scholars.As an essential part of the expressway,ramp has been considered as central node to control the traffic flow on the expressway.The stable traffic flow is always influenced by the cars that would exit the ramp and finally causing certain delays in whole traffic system,especially when some drivers change their lane by force.Therefore,it is of great practical significance to study the lane-changing laws of the ramp location,which will improve the traffic safety and operating efficiency of the expressway,and reduce the impact of the forced lane-changing behavior at the ramp on traffic flow of the expressway.The aim of this paper is to study the law of forced lane-change law at ramp on the expressway,so at the first step,some previous studies the lane-change model and Cellular Automata(CA)were analyzed and some research gap was pointed out.Then,the key rules of the model establishment were concluded,including update rules,boundary conditions and lane-changing requirement.Traditional lane-changing traffic models,such as the NS model and STCA model(STCA-Ⅰ and STCA-Ⅱ aimed at expressway)were introduced.Since the main disadvantage of these models was overlook of the human factors,the introduce of the fuzzy controller in to the model can help to simulate the decision process of the lane-changing.Next,the U.S.Federal Highway Administration(NGSIM)vehicle trajectory data for I-80 and US-101 highways was used to fit the probability function of the lane-changing frequency.The results was further used to establish the relational function between compulsory lane-changing distance and pressure,and the function relationship was confirmed by an expressway data from China.This function was added into the fuzzy lane-changing model,that is,the new compulsory lane-change model,and then compared with the STCA model and fuzzy lane-changing model in the Cellular Automata.The simulated process was composed of the following function,the lane-changing function,the boundary condition function and the front and rear distance function.The finding showed that the new model proposed in this study get the most realistic results.Cellular Automata has the characteristics of time space discretization,which is widely used to solve the traffic flow problem and becomes an important tool to study the operation mechanism of road traffic flow.In this paper,the fuzzy lane-changing model is improved by introducing the studying the lane-changing pressure function which studied by traffic flow characteristics of the freeway ramp exit section.The validity of the improved model is verified by the CA simulation process.The results of the model can provide some reference for the lane-changing research and safe operation of the ramp exit on expressway.