Off-road driving evaluations for persons with cerebral injury: a factor analytic study of predriver and simulator testing.

OBJECTIVES Off-road evaluations composed of psychometric testing and simulator driving are commonly used in rehabilitation settings to assess a person's fitness to resume driving after a cerebral injury. Although the results of these evaluation methods separately provide information about ability to drive, there is no clear understanding about what is measured in comprehensive off-road evaluations as a whole. This study explored the interrelationship of perceptual, cognitive, behavioral, and operational variables that form the basis for off-road evaluations in order to determine whether there are basic dimensions underlying performance in these evaluations and to derive a small set of variables that could help in refining methods for evaluating persons with cerebral injuries. METHODS One-hundred six persons with cerebral damage due to brain injury or cerebrovascular accident were administered a predriver evaluation that consisted of selected neuropsychometric tests. Subjects were also evaluated in a driving simulator that measured their operational responses to filmed driving situations and assessed their behaviors. Principal component analysis was used to identify manifest and latent variables contributing to the results of the evaluations. RESULTS The analysis produced a model with five independent (orthogonal) eigenvectors, or factors, for this population: Higher Order Visuospatial Abilities, Basic Visual Recognition and Responding, Anticipatory Braking, Defensive Steering, and Behavioral Manifestations of Complex Attention. These factors accounted for 66.14% of the total variance in the subjects' responses to comprehensive off-road evaluations. CONCLUSION These factors were useful in understanding driving performance and the role of predriver and simulator testing in driver evaluations.