Safety Characteristics of Exit Section of Multi-lane Expressway

This paper investigated the relationship between traffic safety and the factors of exit opening length and traffic flow rate on the multi-lane expressway. Three different opening lengths were designed for two types of expressway exits and three different traffic flow conditions. 18 driving simulation scenarios were designed and the experiment was performed with 30 subjects for driving simulations. The driving behavior parameters that collected in the experiment included driving trajectory, deceleration, lane change gap, and other driving behaviors of the expressway exit. Then, a comprehensive evaluation of the driving risks was performed for different traffic sign design schemes. The results indicate that the exit opening length has a significant impact on the choice of lane changing points on the opening section under two cross- sectional scenarios. The opening length of 1500 meters would meet the lane changing needs of most drivers. The most common choice of lane changing gap ranging from 5 to 6 seconds. The length of the opening under the separated section has a significant impact on the frequency of the lane changing gap below the critical gap. The flow rate and opening length have no significant influence on the maximum deceleration, the minimum TTC and the distribution position, but the maximum deceleration rate and minimum TTC of the separated section are smaller than those of the monolithic section. In addition, the driving risk of the inner three lanes in the monolithic section is lower than the driving risk of the inner three lanes in the separated section; while the driving risk of the outer lane in the separated section is lower than that of the monolithic section.