A new visibility pre-warning system for the expressway

One of the most important factors that contribute to traffic accidents on the expressway is the low visibility, which may be caused by local or regional weather status such as agglomerate fog, rain, snow and sandstorm. A pre-warning system would be great help to prevent traffic accidents due to low visibility. Considering some problems of the existing system, such as the limited monitoring area and expensive cost, etc., a new kind of visibility pre-warning system is presented in this paper. The pre-warning system is made up of measuring nodes and communications bus. At the measuring node there is a long-distance photoelectric sensor, which is placed by means of cascade at the middle isolation strip along the expressway. Using the long-distance sensors makes it possible to monitor the visibility status of the whole expressway. CAN bus is used in this system as the communication bus to transmit information about visibility along the expressway. In virtue of the advantages of the CAN bus, a long distance network is constructed to meet the needs of the system, such as real time, reliability and low cost. With this new visibility pre-warning system, the visibility status of the whole expressway can be monitored in time and all day. In this paper, the architectural structure of the system is introduced, and also the detailed designs of the measuring node and hardware connection of the CAN bus communications is described.