Research On Traffic Flow Simulation Under The Traffic Accident Condition

With the continuous development of our social economy,people's living standards continue to improve,the national car ownership sharply increased year by year and the traffic demand increase further.Meanwhile,as the aorta of urban road traffic system,expressway is the main channel for the connection between the urban areas,the suburbs,the satellite towns and the external highways.It needs to provide quickly transportation services for the long distance transportation,the external transportation and the transit traffic.As the expressway happen the traffic accident(such as rear-end collision,collide and falling objects,et al.),it is very difficult to remove in a short time.This will be a waste of normal traffic resources and lead to traffic hidden trouble,makes the expressway "fast but not fast".In this paper,the basic section of expressway under traffic accident is studied.Firstly,analyzed the definition and causes of traffic accidents.Furthermore,the paper discusses the interference of traffic accidents to the normal traffic flow from three aspects: the basic parameters of traffic flow,traffic safety and road smooth.Secondly,the paper defines the basic section of expressway under the condition of traffic accident.Based on the analysis of the driver behavior and vehicle behavior,the VISSIM simulation software is used to simulate the traffic accident.Furthermore,explore the parameters of driving behavior and its changes in traffic accidents before and after.In a one-way three lane expressway basic section as an example,analyzed the change of long capacity in different lane,lane length and number of accidents and then the capacity reduction coefficient under different traffic accidents is obtained.The results show that the capacity reduction coefficient is about 48.8% when only one lane is occupied,when occupying two lanes,the remaining capacity of the accident section is less than the original 1/4.Meanwhile,along with the increase of length and traffic accident duration,road capacity loss of more serious.When the accident is 5-20 min long,the actual capacity of the accident bottleneck road is sharply reduced,when the traffic accident time is 20 min,the maximum actual capacity is only 58.31% of 5min.At the same time,the actual capacity of the accident bottleneck roadwill change with the complexity of the vehicle when the equivalent traffic volume of the upstream vehicle is unchanged.Finally,based on the definition of the expressway basic section under the condition of traffic accident,assuming that there is an invisible warning line,by using the cellular automata model,the one-way two lane and three lane expressway basic sections are modeled respectively.The traffic capacity before and after traffic accidents is studied and the traffic flow under the speed limit is further studied.The results show that the residual capacity of the single lane and one-way three lane expressway is one of the first and the second when the traffic accident takes up a lane,which is designed to be 100km/h,which only has the original capacity of 34.33% and 49.84%.At the same time,the speed limit has no obvious effect on the capacity,but the speed limit value has a significant influence on the traffic capacity,when the speed is set to half of the original 50km/h,significantly improved traffic capacity.