Effects of vehicle interior geometry and anthropometric variables on automobile driving posture.

The effects of vehicle package, seat, and anthropometric variables on posture were studied in a laboratory vehicle mockup. Participants (68 men and women) selected their preferred driving postures in 18 combinations of seat height, fore-aft steering wheel position, and seat cushion angle. Two seats differing in stiffness and seat back contour were used in testing. Driving postures were recorded using a sonic digitizer to measure the 3D locations of body landmarks. All test variables had significant independent effects on driving posture. Drivers were found to adapt to changes in the vehicle geometry primarily by changes in limb posture, whereas torso posture remained relatively constant. Stature accounts for most of the anthropometrically related variability in driving posture, and gender differences appear to be explained by body size variation. Large intersubject differences in torso posture, which are fairly stable across different seat and package conditions, are not closely related to standard anthropometric measures. The findings can be used to predict the effects of changes in vehicle and seat design on driving postures for populations with a wide range of anthropometric characteristics.

Crashes and violations among drivers with Alzheimer disease.

BACKGROUND: Several small studies have found a high automobile crash rate for drivers with Alzheimer disease (AD) compared with unaffected elderly drivers, prompting the suggestion that the diagnosis of AD mandate cessation of driving. OBJECTIVES: To compare automobile crash and violation rates of a large number of patients with AD with appropriately matched elderly subjects. To determine if neuropsychological test scores predict these adverse driving events. To determine if intervention by physicians or family members influences driving cessation. DESIGN: Review of crashes and violations from 1986 to 1993 in police-filed Michigan State driving records of 143 licensed patients with AD and 715 licensed comparison subjects matched 5 to 1 in age (+/- 6 years), sex, and county of residence. We correlated crashes and violations with neuropsychological test scores. A questionnaire-based inquiry on the influence of physician, family, and state interventions on driving cessation was administered. RESULTS: The crash and violation rates of patients with AD were not significantly different from those of comparison subjects. However, patients with AD probably drove fewer kilometers than did comparison subjects. Neuropsychological test scores did not predict future crashes or violations. CONCLUSIONS: This study, the largest to our knowledge involving state driving records of patients with AD, does not confirm the previously reported excessive crash rate among drivers with AD relative to an appropriate comparison population. Reduced driving exposure of patients with AD probably kept their crash adverse equal to that of comparison subjects. Intervention by physicians and family members was major factor in reducing driving exposure. These findings affirm that the mere diagnosis of AD does not justify license revocation.