Modeling Run-Off Risk on Interchange Ramps: A Data-Driven Analysis of Driver Behavior

Interchanges play a crucial role in ensuring uninterrupted traffic flow between multiple roadways. The construction of interchange ramps involves horizontal and vertical curvatures to facilitate high-speed and safe traffic transfer. Interchange segments tend to have higher crash rates compared to other parts of the freeway. This research investigates interchange safety by exploring the geometric factors affecting run-off crashes. To accomplish this, 83 participants were monitored using a precision-grade GPS tracker, capturing key kinematic parameters such as speed, longitudinal and lateral accelerations, heading angle, and yaw rate. Participants drove across 34 ramp connectors at six service interchanges in Hyderabad, India. The study developed a new index parameter that combines speed, lateral acceleration, and longitudinal acceleration to assess the risk of run-off on interchanges. This study presents a novel approach to assessing run-off risk on interchanges by incorporating speed, lateral acceleration, and longitudinal acceleration. Further, the study employed linear mixed-effects models to understand the impact of geometric elements on the run-off risk. The results indicate that curvature was the main contributing factor for unsafe travel on diagonal and semidirect ramps. Ramp length was the most significant factor affecting the unsafe distance traveled by drivers on loop ramps. The research findings contribute to a better understanding of the driver’s run-off risk at ramp interchanges.