Influences of Longitudinal Gradient on Traffic Accident Rate Considering Length of Downgrade

Abstract

In order to study the effect of gradient and length of long and steep downgrade on the traffic accidents, the data of 1276 traffic accidents which occurred in 5 different typical downgrades (76.68 km in total length) were collected. According to the distribution of accident amount on the distance between the starting points of the downgrades and accidents spots, the following conclusions can be dawn that (1) the traffic accidents concentrate on the latter half section of the downgrades; (2) the amount of accidents increases with the distance increases. Regressions to the accident rate with the gradient of downgrade of the spots and the average gradient of given downgrade were made using linear and exponential functions separately, and the results of regressions and the coefficient of determination (