Driver response times to turn-in-path events from real world responses in SHRP-2 data

This study analyses of driver behavior in Turn-In-Path (TIP) scenarios using the Second Strategic Highway Research Program (SHRP2) naturalistic driving dataset. A total of 259 real-world incidents, including both crashes and near-crashes, were examined to evaluate human driver perception-response times (PRT) and avoidance behaviors when another vehicle (the principal other vehicle, or POV) turns into the path of a straight-moving subject vehicle (SV). The combined analysis includes TIP events involving POVs turning from intersecting roads to either cross or merge into the SV’s lane. Each event was reviewed to identify the triggering threshold that prompted an emergency response, with measurements taken from video and telematics data. Response time was measured across two different starting points. Key variables included time to conflict, POV behavior (e.g., stopped vs. rolling), SV driver engagement in secondary tasks, and environmental factors such as lighting and roadway geometry. Across both datasets, shorter time to contact was consistently associated with quicker driver responses. In contrast, driver age and gender were not found to significantly affect PRT. This combined study expands the understanding of real-world driver response behavior in TIP scenarios and provides an empirical foundation for refining crash avoidance systems and modeling human performance in traffic conflict situations.