The influence of functional health on seniors' driving risk

Driving safety is important for the growing population of seniors, as driving remains their primary mode of travel in the U.S., and declines in functional health are often associated with driving cessation. As some seniors may have limited or inaccurate insight into their own driving capabilities, a set of objectively measured functional health assessments is needed that could help them and other stakeholders to determine fitness-to-drive. The purpose of the current study was to examine the relationships between senior drivers' functional health and crash risk. This analysis used data from 723 senior drivers enrolled in the Second Strategic Highway Research Program (SHOP 2) Naturalistic Driving Study (NDS). Participants' functional health capabilities were measured using 58 metrics encompassing cognitive, perceptual, physical, psychomotor, and psychological abilities as well as driving knowledge. The mileage driven and crashes were identified from objective NDS data. Twenty-two of the metrics were statistically significantly associated with crash risk. Deteriorated functional health was uniformally associated with increased crash rate. These findings provide key information to support the development of a battery of functional assessments for senior drivers who may need to have fitness-to-drive screening.