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The Role of Driver Distraction in Traffic Crashes

Driver distraction is a major contributor in traffic crashes

Driver inattention is a major contributor to highway crashes. The National Highway Traffic Safety Administration estimates that at least 25% of police-reported crashes involve some form of driver inattention.

Driver inattention is a major contributor to highway crashes. The National Highway Traffic Safety Administration (NHTSA) estimates that approximately 25% of police-reported crashes involve some form of driver inattention – the driver is distracted, asleep or fatigued, or otherwise “lost in thought” (Wang, Knipling and Goodman, 1996; Ranney, Mazzae, Garrott and Goodman, 2000). Estimates from other sources are as high as 35-50% (Sussman, Bishop, Madnick and Walter, 1995; NHTSA, 1997).

The AAA Foundation for Traffic Safety (AAAFTS) is committed to educating the public about issues affecting safety on the roadway. A contract was awarded to the University of North Carolina Highway Safety Research Center to conduct research on “The Role of Driver Distraction in Traffic Crashes.” The goal of the project is to identify the major sources of distraction to drivers and the relative importance of different types of distractions in causing crashes. The project involves a number of distinct yet interrelated tasks, including: analysis of crash data from the NASS Crashworthiness Data System (CDS) data file; analysis of narrative data from CDS and North Carolina crash reports; and collection and analysis of field data to determine the prevalence and implications of selected driving distractions in real-world driving.

This report documents the work carried out to date on the project, focusing on the CDS and North Carolina data analyses. AAAFTS has chosen to focus its efforts specifically on driver distraction, rather than the broader category of driver inattention. It defines distraction as “when a driver is delayed in the recognition of information needed to safely accomplish the driving task because some event, activity, object, or person within or outside the vehicle compelled or tended to induce the driver’s shifting attention away from the driving task.” The presence of a triggering event distinguishes a distracted driver from one who is simply inattentive or “lost in thought.”

Safety problems related to driver inattention and distraction are expected to escalate in the future as more technologies become available for use in personal vehicles. During the summer of 2000, NHTSAhosted an Internet Forum on the safety implications of driver distraction when using in-vehicle technologies including cell phones, in-vehicle navigation systems, night vision systems, and wireless Internet (Llaneras, 2000). The Forum attracted broad international participation from both the public and private sectors. While cellular telephones and other in-vehicle technologies have been the focus of considerable research within the highway safety community, much less attention has been given to identifying other, non-technological, distractions within the vehicle and their potential role in causing crashes. The last in-depth crash causation research was sponsored by NHTSA and conducted at Indiana University during the mid-1970s (Treat, Tumbas, McDonald et al., 1979). This study, frequently referred to as the Indiana Tri- Level Study because of the three levels of crash investigation employed, examined the human, environmental, and vehicular factors in traffic crashes.

Study results identified human factors as probable causes in 93% of the investigated crashes, environmental factors as probable causes in 34%, and vehicular factors as probable causes in 13%. Internal distraction was cited as a causal factor in 9% of the crashes and driver inattention in an additional 15%. No information was reported on the frequency of external distractions.