Exploring the effects of critical driving situations on driver perception time (PT) using SHRP2 naturalistic driving study data

Driver PT is critical when a driver faces an imminent crash risk and needs to determine what evasive maneuvers to execute. Therefore, it is of utmost importance to study how PT varies across different critical driving situations. PT refers to the time drivers need to recognize the nature and significance of external stimuli. Driver PT is critical when he or she faces a potentially hazardous driving situation, and must determine what action(s) or evasive maneuver(s) to execute. Although past research has identified many factors associated with PT, little research has been done on the effects of critical driving situations on PT, let alone in a real-world driving environment. Naturalistic driving study (NDS) data provides an unprecedented opportunity to look into PT prior to the occurrence of safety-related events. This study seeks to shed light on how critical driving situations influence driver PT, as well as how the driving environment and driver behavior affect PT during real-world driving by utilizing the Second Strategic Highway Research Program (SHRP2) NDS data. An NDS consists of two primary features that distinguish it from retrospective approaches: vehicles are equipped with video camera technologies that observe the driver and the road ahead of the vehicle continuously while driving, and drivers are asked to drive as they normally would. To best study PT while minimizing the effects of confounding factors, this study focused on a total of 1417 rear-end crashes and near crashes. It was found that critical driving situations, the driving environment, and driver behavior are all influential factors in explaining the variation of PT among different drivers. The longest PTs are during critical driving situations where the vehicle ahead is stop-and-go, which can be as long as 2.84 s while controlling for the effects of driving environment and driver behavior factors, compared to other types of driving situations such as a vehicle ahead decelerating or lane changing.