Impact of Slip Lanes on Pedestrian Safety at Roundabouts Considering Autonomous Vehicles

The emergence of autonomous vehicles (AVs) presents significant transformative potential for modern transportation systems, particularly concerning pedestrian safety at roundabouts with heterogeneous traffic conditions and slip lanes. Slip lanes influence the dynamics of right-turning traffic by increasing vehicle speeds, reducing driver visibility of pedestrians, and altering merging behaviors, thereby elevating pedestrian conflict risks. (Note: This study applies to road systems where vehicles drive on the right-hand side.) This study investigates how different slip lane designs affect pedestrian safety, utilizing simulation modeling calibrated with field trajectory data. The findings indicate that vehicles in slip lanes typically maintain higher speeds than those in approach lanes, enhancing risk at entry and exit points. Notably, the presence of AVs significantly reduces pedestrian conflicts; with AV penetration at 75%, conflicts decrease by 34.62%, highlighting AVs’ potential to improve pedestrian safety. Moreover, the study provides targeted recommendations for slip lane configurations based on pedestrian activity levels: free-flow lanes are advised in areas with low pedestrian traffic to minimize delays while maintaining safety; yield-controlled lanes are preferred in medium-traffic areas for balancing flow and safety; and traditional roundabout designs are recommended for high pedestrian volumes because of their effectiveness in reducing pedestrian-vehicle conflicts. The study also emphasizes the importance of prioritizing safety enhancements, such as adjusting slip lane curvature and optimizing crosswalk positioning, particularly at entry sections of the slip lane where pedestrian exposure is highest.