Research On The Variable Speed Limit Method Of The Topical Rainfall Segment On Freeway

With the extending of the highway and the increasing number of vehicles, the traffic accidents ofen happen. According to the statisties data from Ministry of Publie Security Traffic Management Burean, Speeding is the main reasen to the traffic accidents, however,we adopt the constant speed limit currently which cannot adjust the speed limit dynamicly on the basis of the traffic state and the weather condion. As we know, the rainfall is one of the most common weather phenomenon espacially the rainstorm or thundershowers which offen happens on the topical segements of the highway in the summer.Generally this rainfall on the topical segements oftend lead to form a bottleneck which will affect the safety as well as efficency of the highway. So we must adopt suitable speed limit strategies given the rainfall on the topical segements.In this article, the macro dynamic traffic flow model is stdudied on the basis of deep research that how the traffic flow characterastics such as velocity、flow rate and capacity is effected by a certain intensity of rainfall. We then establish a variable speed limit model of the topical segment on the highway considering the effect that a cetain intensity of rainfall has on the velocity of vehicles and the capacity of the segement.Finally a simulation experiment of the model is given,and the result of the simulation show that the speed limit model has certain practicability.The content of this article is presneted as follows:(1) Acorrding the field measurements of the traffic flow, we firstly compare the charecteristic paremetes such as velocity and flow rate under the rain day with that on the norman day. A traffic flow model about the rain fall is presnted on the basis of the degree that cetain intensity of rainfall Impact on the traffic flow.(2) We extend the famous macro dynamic traffic flow model METANET to present a variable speed limit model of the topical segment on the highway on the baisi of the reserch on how the rainfall impact the charecteristic paremeters. we then establish the objective function which aims to minimum the totle time spent on the upstream segments of the topical rainfall sgement subjected to the max operating velocity and the capacity of the rainfall segement and the speed variance between the adjecent road segments and the adjecent time segments. Finally this paper establish a optimal control variable speed limit model of the topical rainfall segment on freeway adopting a sliding windows technique.(3) This paper presents a simulation experiment to verify the effectiveness of the a optimal control variable speed limit model of the topical rainfall segment on the highway through editing a program on the Matalab7.0The result of the simulation show that the speed limit model has certain practicability to improve the oprerating efficiency and the safety of the topical rainfall segment on freeway.