Theoretical Calculation of the Maximum Speed Limit Value on Freeway in Adverse Weather

In order to increase driving safety level on freeway, the paper analyzed the affecting mechanism of rainy day, snowy day and foggy day on road traffic safety. Considering that the sum of running distance and braking distance is less than visible distance, theoretical calculation formula of maximum speed limit value on freeway in adverse weather was presented based on the safe distance. Suggestions values of corresponding speed limit were given according to different visible distance, road fiction coefficient and grade.