Design of on-road test routes: validity issues for assessment of functionall impaired drivers

Licensing authorities are faced with the challenge of designing on-road assessment procedures that are both valid and reliable. In the case of drivers with diagnosed medical conditions or disabilities, requirements for valid assessment need to be considered in relation to the kinds of functional impairments that might reduce driving competence and increase crash risk; an important determinant of assessment validity is the kind of test route used. This paper describes the characteristics of routes, including associated driving manoeuvres and traffic conditions, which are currently being used in Victoria by specialist occupational therapy driver assessors (OTDAs).
Data were obtained by in-depth interviews of 22 OTDAs, representing 50% of the total group active in Victoria at the time of this study; seven were based in rural or regional locations. All OTDAs reported using a standard test route for clients seeking an open (i.e. not geographically restricted) licence. Compliance with professional guidelines was very high for items designated as compulsory, but was more variable for those categorized as desirable. As well as variation between routes in numbers of each main type of driving manoeuvre, differences between rural versus urban routes were noted, with those in rural areas being less cognitively demanding. Implications for more detailed specifications of standard route requirements for such assessments are discussed, focusing particularly on requirements to achieve greater validity.