The purpose of this study was to quantify naturalistic driver behaviour during real-world rear-end collisions. Rear-end collisions from the 100-car naturalistic driving database were reviewed and behaviour of drivers in the struck vehicles (i.e., lead vehicles) were analyzed. Results indicate that rear-ended drivers disengage their foot from the brake pedal and then reapply within average perception and response intervals (0.90 seconds; 0.15 SD) and braking intensities (0.50 g; 0.27 SD) consistent with visual detection of immediate collision hazards, despite the added complexity of a multi-sensory collision experience. Together with previous research, these data suggest that perception and response durations and braking intensities are scaled to the severity of the detected hazard. This research has applications to forensic investigations of collisions in which the inclusion of driver behaviour data is a requisite to quantifying impact dynamics and the analysis of collision avoidance potential in real-world conditions.