Analyse The Problem For Freeway Speed Limitation Under Unfavorable Weather Condition

As the increasing of countrywide freeway traffic mileage, the ratio of traffic accidents increases and the problems of traffic safety stand out day by day. Unfavorable weather is the great hidden trouble of road safety on the freeway, how to assure the traffic safety under unfavorable weather have become the issue of social safety that every country values. Aiming at analyzing systematically on the measures of freeway speed-limits.(1) The paper emphatically analyzes the relationship between the speed and traffic safety, unfavorable weather and traffic safety. The influence of speed on the driver, the influence of speed on the vehicle, the influence of speed on the traffic accident are analyzed in term of the relationship between the speed and traffic safety. As the relationship between unfavorable weather and traffic safety, the paper emphatically discuss the impact of several weather to the traffic safety, such as fog, rain, snow and so on.(2) Firstly the speed scheme is classified simply, then how to choose the speed scheme is discussed,such as the factors which is needed to be considered and the steps of speed scheme, finally how to choose the speed scheme is explained briefly through the example.(3) The paper analyzes the affecting mechanism of adverse weather conditions on road traffic safety such as rain, fog et al, Using the method of mathematics formulas derivation, calculation formula of maximum speed limit value was presented based on the safe distance and the suggestions of corresponding speed limit standards were given.(4) The speed limit standard under the low visibility situation are simulated and estimated by VISSIM software.