Study on lane-changing success rate and advance guide signs location for eight-lane expressways

The strategic placement of advance guide signs (AGSs) is crucial in ensuring optimal driving efficiency and safety at expressway exits. However, the extant literature contains a paucity of research on the placement distance of AGS at expressway exits. The objective of this study is to establish the optimal design for AGS at exit ramps on eight-lane expressways across varying levels of service (LOSs). The present study establishes a bidirectional eight-lane vehicle lane-changing model by integrating a selection of vehicle lane-change points (pre-lane change), minimal safe distances between preceding and following vehicles (post-lane change) and the vehicle lane-changing process. Subsequently, a method for calculating the lane-change success rate on expressways is proposed. Finally, the success rate of vehicles exiting the eight-lane expressway under four LOS conditions was calculated using conditional probability while also investigating the relationship between the AGS deployment location and the expressway exit success rate. To ensure a high driving-out success rate across various LOSs, it is recommended that AGSs be positioned at distances of 3.5 km, 2.5 km, 1.5 km and 0.9 km from the exit ramp. The research findings can supplement the existing specifications for AGS deployment on expressways.