Naturalistic Studies (Driving In Traffic) continued...
In the study described by Janke (2001) and Janke and Hersch (1997), 75 subjects age 60 to 91, who were referred to the DMV from various sources for reexamination, were compared to 31 paid “volunteers” age 56 to 85, who were recruited through signs posted at study sites or word-of-mouth. Analyses were performed to determine if the MDPE could discriminate between the referral and volunteer subjects, and if it could discriminate between the cognitively impaired and cognitively unimpaired referral subjects. Results indicated significant correlations between the following driving measures and group (referral versus volunteer): unweighted errors (.460); weighted errors (.470); hazardous errors (.388); critical errors (.386); and confusion errors (.418). Test failure was not significantly correlated with group. The following variables were also significantly correlated with age: unweighted errors (.395); weighted errors (.409); and critical errors (.355).
Cognitively impaired referrals had significantly more “confusion errors” than cognitively unimpaired referrals. However, there were no significant differences between cognitively impaired referrals and cognitively unimpaired referrals on total errors, critical errors, or hazardous errors (although every driving measure showed a directional difference in favor of the cognitively unimpaired subjects). The authors emphasize the value of “confusion” errors for predicting cognitive impairment, and suggest that a standardized test for older drivers who are experienced but possibly cognitively impaired should contain a task similar to the destination-finding task in the MDPE, i.e., a task that demands more than passively following an examiner’s instructions. In future work undertaken by NHTSA to investigate drugs and driving, such a task could help identify subjects who are cognitively impaired as a consequence of taking sedating medications or medications that cause deficits in concentration, or combinations of medications that result in such cognitive deficits.
Di Stefano and Macdonald (2003) conducted a retrospective case review study using data from 533 road tests performed by drivers referred for a VicRoads ( Victoria, Australia) licensing review test to obtain detailed information about the types of driver errors most characteristic of unsafe drivers. The average age of the tested drivers was 76.1, with a range of 24 to 100; 47 percent of the drivers were older than 80. The purpose was to develop an improved procedure for occupational therapy assessments of functionally impaired and older drivers, with a focus on optimizing the performance scoring system used in the tests.
The “on-road review test” was given to drivers referred to VicRoads because of a concern about their driving competence, but who had not been identified by their physician as having “complex medical conditions or significant cognitive impairment.” It was administered by a VicRoads License Testing Officer (LTO) who specializes in older driver testing. The test was conducted in an automatic dual-control car, beginning at the driver’s home and encompassed routine travel destinations (shopping, doctor’s office, etc.). The routes were therefore not standardized. Drivers were provided with an initial familiarization period in the vehicle, and were then tested during a 30- to 45-minute period, usually in off-peak traffic conditions.
Criteria used to score driver performance included errors in each of six main categories: intersection negotiation, lane changing/diverging, speed and position on road, safety margin, car control, and low-speed maneuvers. The LTO used a scoring sheet that lists each performance category, and within each category, a list of separately scored behaviors was also scored. Behaviors were recorded as “satisfactory” or “unsatisfactory” and comments were made only to document details. If an LTO needed to intervene to maintain safety, this was recorded as “LTO intervention” in relation to the driver performance category, and the context in which the intervention was documented.