Studying on variable speed limit for expressway based on meteorological monitoring

This paper analyzed the traffic accident which offen happened in bad weather conditions and put forward measures. The vehicle´s speed limit value is calculated according to the auto brake mathematical model, the weather visibility and the variation of surface adhesion coefficient. In order to realize the vehicles safe driving in different sections according to different speed limit requirements, a vehicle speed limit alarm device is designed and automatic weather stations are improvely designed. The automatic weather stations in different sections are regared as web coordinator and the vehicle speed limit alarm device is treated as network terminal node in this paper, realizing wireless communication between automatic weather stations and vehicles using ZIGBEE wireless networks. The web coordinators send different speed limit value associated with the meteorological information to nodes timely, and so realizing the vehicle speed change safe driving.