Taxonomy of Older Driver Behaviors and Crash Risk: Appendix C

This project’s objectives were to identify risky behaviors, driving habits, and exposure patterns that have been shown to increase the likelihood of crash involvement among older drivers; and to classify these crash-contributing factors according to a set of underlying functional deficits specific to, or more prevalent among, the older driver population. Such deficits may result from normal aging, age-related medical conditions, or medication use. A further goal was to identify and critically examine behavioral countermeasures with the potential to mitigate functional loss and/or diminish the occurrence of risky behaviors—and thus ameliorate crashes among older drivers. The first task was an analysis of older driver injuries and fatalities using national databases (FARS, GES), to identify driving patterns, driving tasks, and contributing factors associated with crashes by older drivers; more details are available in a separate document, Report No. DOT HS 811 093, “Identifying Behaviors and Situations Associated With Increased Crash Risk for Older Drivers.” Additional project tasks included a review of the literature describing age-related functional changes, and evaluations of existing behavioral countermeasures to reduce older drivers’ crash risk; an expert panel meeting to supplement the information from the database analyses and literature review; and unstructured interviews with older drivers who have had crashes within the previous three years, and an age-matched group who have not had crashes within that period, to determine whether these groups differ in factors such as exposure or use of countermeasures. The outcomes of these project activities were used to develop and refine a taxonomy table that captures critical relationships between topics and subtopics highlighted in the literature review and crash database analyses. This table identifies critical performance errors that underlie crash types where older drivers are most strongly overrepresented; the functional deficits that are implicated in causing such performance errors; and the countermeasure strategies that presently appear to hold the greatest promise to ameliorate or to accommodate those (age-related) deficits. The taxonomy table is a resource that provides at-a-glance, state-of-the-knowledge information to assist researchers, health care practitioners, and others concerned about older driver safety to identify particular risk factors, and what can be done to reduce the risk. A hard copy version and an expanded, electronic version of this resource were developed.