Crash Prediction Model and Its Prevention Method for Consecutive Downgrade Section

This paper attempts to examine the relationship between crash occurrence and the geometric characteristics of consecutive downgrade section in China. A sample of 13 km of a consecutive downgrade section was selected in this paper. A total of 325 crashes were collected for the 2 years period. Two section divided method were adopted, which produced one km fixed-length segment and the longitudinal grade consistent segment. Three general form of crash frequency prediction models were constructed, which are crash frequency hourly prediction model, crash frequency weekly prediction model and crash frequency monthly prediction model. Four kinds of prevention schemes were put forward, and three crash prevention models were used to re-estimate the crash frequency under the condition of four kinds of prevention schemes. A before-and-after study was carried out to analyze the prevention effect of four kinds of prevention schemes under the condition of both with and without prevention scheme. The results indicate that the fixed-length segment divided method is appropriate for complex alignment section. The economic benefit of scheme 1 and 2 are not significant, but the economic benefit of scheme 3 and 4 are significant. It was interesting that cost-benefit ratio increased gradually with the increase of input cost, and the cost-benefit ratio began to decline while input cost went up to a certain extent.