The Study On Variable Speed Limit Management System For Highway Under Adverse Weather Condition

The weather is an important factor of which could affect road traffic safety and efficiency. The adverse weather causes more accidents and road-closed, which is a serious threat to people’s lives and property. Based on consulting a large number of papers about the meteorology of the traffic and freeway management at home and abroad, a new variable speed limits (VSL) management system which is based on real-time weather information around the freeways was designed in this paper.This paper first analyzed the impact of bad weather to road traffic. The study found that under the influence of adverse weather, the reducing of effective the range of visibility and road friction make traffic safety performance down. And then, the fully safe speed and anti-rear-end safe speed computational model were designed. The model used the number of visibility range and road friction as the main parameters. According to this model, the VSL rule that would be adopted in the adverse weather conditions were designed. The simulation results showed that when the road traffic conditions change, implementing high-quality VSL management can smooth traffic flow, reduce the incidence of accidents and mitigate congestion. In order to get better affection when implementing VSL management, a new vehicle mounted device was developed. With the ZigBee and GPS, the device could receive the real-time weather information from the automatic weather stations sited along the freeway, and according to these messages automaticly set a reasonable limit which is suitable for the current environment. Meanwhile, the device can guide and monitor drivers’action. Once the vehicle speeding, it could record the violation action. Finally, according to the functions of the vehicle mounted device, the VSL management information system was developed. With this management information system, staff can search the vehicle running information stored in the vehicle mounted device, and know about the status of vehicle on the way. Thus, it could strengthen the management to the behavior of the vehicles, and improve the management effectiveness of VSL.The freeway variable speed limits management systems designed in this paper react more flexible and accurate in the adverse weather. It could improve and supplement the existing freeway meteorological disaster warning system, and have a positive effect on keeping freeway traffic safety and smooth.