Driving instructor interventions during on-road tests of functionally impaired drivers: implications for test criteria

Licensing authorities world-wide are facing the challenge of how best to assess the performance of drivers who are functionally impaired; of particular concern are those with cognitive decrements that have been associated with the elevated crash risk of older drivers.  This study examines the types of driving errors associated with driving instructor interventions (DIIs) to maintain safety during tests conducted by specialist Occupational Therapists (OT) of drivers with diagnoses likely to be associated with cognitive impairment.  DIIs have been found to be critical determinants of test outcome, so understanding the error patterns associated with them is an important pre-requisite to improving the validity and sensitivity of driver evaluation criteria in such tests.

OT reports to a licensing authority of all on-road assessments of drivers with possible cognitive impairment during a specified period were randomly sampled. A total of 256 report files were reviewed; average driver age was 60 years, 64% were male and the most common diagnoses were CVA, dementia and behavioural disorders. In most cases (86%) the tests had used a standardised route and procedure, rather than being ?local area? tests. The most frequently reported driving errors were associated with intersection negotiation, lane changing/diverging and position on the road, and at least one DII was recorded for 27% of the sample. Errors associated with DIIs were highly predictive of membership of the fail group ? a relationship supported by other researchers. The error patterns displayed by this group are similar to those identified in groups of older drivers ? a finding consistent with previous research.

Results will be presented in relation to international research and the authors? previous findings concerning driving errors reported during older driver ?review tests? by a licensing authority. The potential role of DIIs in evaluating the performance of older and/or impaired drivers will be discussed.