Dangerous sections such as curves, long slopes, tunnel entrances and exits are prone to serious traffic accidents under severe weather conditions such as fog, rain and snow. The research shows that no matter what the climate and road conditions, the core cause of the accident is that the driver can't understand the road information in advance, is negligent in consciousness, and drives improperly (such as driving too fast). In the past, the prevention of traffic accidents in dangerous sections mainly relied on static facilities such as reflective road signs, guidance signs and warning signs, with limited effect. In view of the impact of low visibility weather such as fog, rain and snow on vehicle traffic, safe driving in fog area and anti fog guidance intelligent system ensure driving safety. The company puts forward the advanced safety concept of "prevention first, protection combination, active guidance and passive protection", and develops the "intelligent guidance and collision avoidance system in fog area", which makes up for the shortcomings of the traditional safety guidance system, and can meet the requirements of vehicle driving speed limit and safety distance limit under severe weather conditions such as heavy fog, and reduce the impact of low visibility weather on fog The impact of vehicle traffic, improve road traffic safety. 1.2 safe driving risk in high-speed fog area. If the condition of road vehicles can be detected automatically, the driver can be warned in time when the front vehicle is too close to the rear vehicle, and the driver can be urged to slow down to avoid the rear end event as much as possible. 1.2.2 it is not easy for vehicles to recognize the road outline in the fog area. From the road point of view, the visibility is low in the fog weather, the lane line is fuzzy, and the driver can not see the road outline, markings and various traffic sign signs in front, so it is easy to drive out of the road boundary, especially at the road section where the road turns. 1.2.3 once a traffic accident occurs in the secondary accident fog area which is prone to continuous rear end collision, the accident vehicle stopped in the middle of the road has become a dangerous obstacle. If the rear vehicle cannot be warned in time, it is very easy to cause the rear end collision of two vehicles, so the continuous rear end collision in the fog area is often encountered. 1.3 the intelligent guidance and collision avoidance system in fog area of expressway is an intelligent all-weather unattended system, which integrates meteorological monitoring, intelligent lights, sound and light alarm, traffic information display screen and other equipment. It is often used in dangerous road sections (especially in fog area), and can effectively solve the traffic safety problems of dangerous roads.