Speed Limit Model of Expressway in Rain and Fog

In bad weather such as rain and fog, the probability of traffic accidents on expressways increases significantly. If the limit speed is set too low, although the safety will be increased, traffic efficiency will be greatly reduced. At present, speed limit models in bad weather are mainly based on qualitative classification, but lack of quantitative calculation. Based on the theory of stopping-sight-distance model, hydroplaning model and rollover&sideslip model, this paper proposes a speed limit calculation model of expressway in rain and fog scene, taking rainfall intensity, visibility, road friction coefficient and water film thickness as quantitative input parameters, and divides the speed limit value into limit speed, recommended speed and safe speed, in order to improve traffic efficiency. Finally, based on the parameters of a highway section, a variable speed limit strategy is proposed in rain and fog scenes.