Safety factors of exit slip roads on China's urban motorways

Abstract

The number of crashes occurring on motorway exit slip roads is approximately double that occurring on entrance slip roads. A crash on an exit slip road usually causes a decrease in its capacity, leading to queues forming on the main carriageway. The aim of this paper is to evaluate the safety factors for exit slip roads on urban motorways in China. Seventy exit slip roads on motorways in Shanghai were selected for statistical and regression analyses. Negative binomial models were established to identify the influencing factors. The regression results indicate that the slope of the exit slip road, the length of deceleration lane, the length from the slip road terminal to stop line, the exit slip road type and the average annual daily traffic are significant factors with respect to the safety performance of exit slip roads. Compared with previous studies, urban motorway exit slip roads in China have complex and specific influencing factors. With the exception of the geometric design of exit slip roads, the slip road–street intersection serves an important role in slip road safety.