Examining the effects of improved signs on lane-changing behavior at expressway emergency stop area

OBJECTIVE: The emergency stop area at expressways is designed to help drivers handle emergencies. However, to enter the emergency stop area, some risky lane-changing behaviors often occur. This study evaluated drivers' lane-changing behavior under various sign schemes to identify an effective sign scheme that can improve lane-changing performance when entering the emergency stop area. METHODS: Based on the pre-position distance, disappearance distance of the signs, as well as the driver's judgment distance and action distance, different sign positions and number conditions were set. A driving simulator was used to examine drivers' lane-changing behavior when approaching the emergency stop area under various sign schemes. The lane-changing behavior was divided into the decision process and the action process. The Generalized Estimating Equations (GEE) model was used to analyze five selected behavioral variables. Besides, the entropy-weighted TOPSIS model was employed to select the recommended sign scheme. RESULTS: The results show that both the Single position improved (SPI) sign and the Two-stage improved (TSI) sign effectively advanced the drivers' lane-changing position by over 52.4%, increasing the lane-change success rate by more than 23.8% compared to the baseline sign. The TSI sign further increased the lane-changing speed and improved comfort compared to the SPI sign. The entropy-weighted TOPSIS model results identified TSI380 as the recommended sign scheme. Additionally, mature drivers performed better in lane-changing performance than novice drivers, and female drivers were more likely to follow the sign information. CONCLUSIONS: The findings provide scientific guidance for the placement of signs before emergency stop areas. It is recommended to set signs at 380 m and 230 m before the entrance of the emergency stop area to reduce risky lane-changing behavior.