Driver’s perception-reaction time (PRT) is critical when drivers need to excute evasive manuevers to avoid a crash. Driver’s PRT refers to the time drivers need to perceive stimulus, decide what to do, and react to this stimulus. PRT include (1) mental processing time, (2) movement time, and (3) device response time, where mental processing time can be futher decomposed into (a) sensation: to detect an object in the roadway; (b) perception: to recognize the meaning of the sensation; and (c) response selection and programming: to decide which response to make and to mentally program the movement. Many research has shown the significant effects of PRT on crash occurrence.

Past research have identified many factors associated with PRT, but little research has being done to quantify the effects of these factors on PRT, let alone their effects during real-world driving. Green (2000) reviewed extensive research on PRT and concluded that one of the most critical variable in terms of PRT is “driver expectation.” Also, many research reported that impairment and distraction (e.g. cellphone usage) would increase PRT. While driver expectancy, impairement, and distraction are prevelant in real-world driving, their effects varied across different driving environment. The naturalistic driving study (NDS) data provides an unprecedented opportunity to look into PRT prior to the occurrence of safety-related events (crashes and near crashes). This study seeks utilize the SHRP2 NDS data to shed more light what factors would affect driver’s PRT during real-world driving and quantify their effects on increasing or reducing PRT.