Research And Implementation On Variable Speed Limit Control System For Freeway Under Rain Weather

With the rapid increase of highway mileage and vehicle amount， trafficaccidents occur frequently， and speeding is the main cause of traffic accidents. Atpresent， our country highway mainly using fixed speed limit to ensure the safety oftraffic which cannot be dynamically adjusted according to the traffic situation ormeteorological environment， is bound to affect the highway traffic safety. Rainfall isone of the most common weather phenomena in China， especially in the summer，thunderstorms， heavy rain and other kinds of rainfall are very common.Rain insome parts of the road section can easily lead to highway traffic bottleneck.Therefore， it is essential to adopt the appropriate highway speed limit controlmeasures local to rainfall parts of the road section.Based on the summary of the existing research on realizable speed control,combined with the effects of rainfall on expressway traffic flow parameters, fullyconsidered the rainfall changes in time and space, this paper establishes the highwayrealizable speed control model and control methods under variable rainy environment.And, this paper completes evaluation and analysis of control model and controlmethods by using traffic simulation software VISSIM for real-time online simulation.Last，the design and Realization of the system software by using traffic simulationsoftware VISSIM as a network server, the COM interface of simulation softwareVISSIM as the data transmission channel, and using VB.NET programming languagewriting control algorithm under Visual Studio2008environment. The main contentsare as follows:（1） The overall design of the VSL systemAccording to different user needs, design the equipment laying of systematicfield, analyze the functional requirements of the system, divide the function modules.According to the functional requirements, design the data logic structure of system.From the perspective of software design divide module of software design. Then,according to the key contents of this paper, establishes the software architecture of the system, introduces the design method of database, and describes the design scheme ofthe system broadly.（2）Research on traffic flow model under the rainy environmentStudy the relationship between highway traffic flow parameters, analyze thevarious traffic flow model of expressway, chose the cell transmission model as thebasic variable speed limit model combined with the need of this study. Then, based onthe analysis of the highway cell transmission model under sunny conditions,introduces the variation of rainfall influence on model, establishes the celltransmission model under rainy environment. Finally, introduce the effect of variablespeed limit control on the model, establish the model of highway variable speedcontrol under rainy environment.（3）Research on variable speed control methodPut forward the basic strategy of variable speed control on rainy day, studyvariable speed control method based on Model Predictive Control, establish theoptimization objective function of the system, and a detailed description of the wholecontrol process of Model Predictive Control.（4）Policy experiment and software design of the systemBased on traffic simulation software VISSIM, COM interfaces technology ofVISSIM, using VB.NET programming language to achieve online simulation controlmodel and control algorithm, complete the verification of the system model, andcompletes the system software according to the overall scheme of the system.