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Conventional forensic analyses of collision avoidance behaviours involve assigning a perception and response time (PRT) interval to a driver which precedes the onset of evasive action. This approach relies on the investigator identifying a ‘time zero’ for when to begin the PRT interval, which nominally aligns with the first moment of hazard detection. However, depending on the incident circumstances, identifying the initial moment of hazard detection poses challenges. Recent research has shown the potential of an alternative method of forensic analysis that is based on the relationship between response onset and the projected time-to-impact (TTI). Accordingly, the aim of this research is to further investigate this relationship. Twenty subjects viewed driver-perspective recordings of a simulated vehicle travelling down a major roadway past several two-way stop-controlled minor roads. At various intersections, intruding vehicles entered from the left or right.

Immediate collision hazards pose obvious threats to approaching drivers and therefore provoke emergency evasive responses. When the hazard is a vehicle intruding into the lane ahead, how its movement characteristics influence an approaching driver’s response is not well understood. This study examined the relationship between intruding vehicle motion and hazard perception. Seventeen subjects viewed first-person perspective recordings of a simulated vehicle travelling down a two-lane roadway containing several intersections with stop-controlled minor roads. Stopped vehicles were located at approximately half of the minor road intersections. Throughout the study, some vehicles (termed ‘intruders’) accelerated into the subject’s lane of travel at 1 of 6 pre-determined acceleration rates. Subjects were instructed to ‘brake’ their vehicle by pressing the space bar on a keyboard as soon as they perceived that a collision was imminent.