Research On The Relationship Between Speed And Safety For Freeway

Freeways are playing an important role in comprehensive transportation system in our nation. However, besides high efficiency and fleetness and conveniences, there are large numbers of accidents and casualties on freeways. Compared with the developed countries, freeway accidents are especially severe in China. Speed limit is one of the main measures to improve traffic safety level. It is significant to improve the safety level on freeways by analysing the relationship between speed and safety in time and discussing speed limit methods according as the situation of China.Firstly, safety problems that exist on freeways in China and the researches about the relationship between speed and safety both at home and abroad are summarized in the dissertation. Then the relationships between design speed, operating speed, limited speed etc. are expatiated. At the same time, analyzes the speed affected factors from the point of view of human, vehicle, road alignment, environment and management. The conception of advisory speed limit is introduced into.Secondly, theory of the relationship between speed and safety is studied including the relationship between speed and accidents, accidents severity and geometric alignments. The case of research on speed control for Sanfu freeway is seleced. Great deals of data were investigated to analyze operating speed forecast and harmonization. Models of the relationship between operating speed and alignment elements, operating speed and accident frequency, speed relevant statistics are set up by means of regression analysis using software SPSS. And then draws a conclusion that speed differential is the most important factor to affect travel safety. But the actual speed control method only considers the design speed.Finally, aiming at speed limit problems on freeways in China, series of countermeasures adapted to freeways in our country are put forward. Meanwhile, speed limit flow chart is also provided. The production of the paper can be used for reference to speed limit establishment for other freeways and supporting issue of the speed limit criterion in China.