Driver-Related Delay in Emergency Braking Response to a Laterally Incurring Hazard

Abstract

Collision analysis often assumes emergency deceleration begins immediately upon completion of the vehicle’s mechanical brake lag. The goal of this study is to determine the driver-related delay from initial brake application to various degrees of deceleration in a simulated emergency and to test variables contributing to the modulation of driver braking. Using the data of Mazzae et al (2003), in which drivers respond to a lateral vehicle incursion, we have assessed the contribution of Time-to-Intersection (TTI), road condition, gender and crash outcome on driver emergency brake response. In the first 0.3 second phase after initial brake application, vehicle behavior was similar across all variables as drivers reached only moderate levels of deceleration. In the second phase, drivers often took more than one second to reach emergency decelerations, especially with a longer TTI. Pavement condition, gender and crash outcome were not significant factors. We discuss the consequences of driver braking behavior in the context of driver feedback and accident reconstruction analyses.