Assessing Fitness to Drive

The evidence that underpin the licensing criteria and guidance are sourced from medical and fitness-to-drive studies, medical guidelines and expert opinion. A reference list of important studies is provided at the end of each chapter. In addition to evidence regarding crash risk and the effects of medical conditions on driving, evidence has also been sought regarding best practice approaches to driver assessment and rehabilitation.

A key input in terms of evidence for the licensing criteria remains the Monash University Accident Research Centre report Influence of chronic illness on crash involvement of motor vehicle drivers: 3rd edition. This is an update of the second (2010) edition of the report and provides a comprehensive review of published studies involving drivers of private and commercial motor vehicles. The report investigates the influence of selected medical conditions and impairments on crash involvement, in the context of condition prevalence and quality of evidence of crash involvement.^1,2

In compiling this report, the Monash University Accident Research Centre led an international research consortium to compile, review and interpret the best available evidence on each topic. Nevertheless, for most conditions, the report acknowledges the limited evidence available and that the quality of evidence is variable. In interpreting the research, there is therefore a need to consider several sources of potential bias including the following:

• There is a ‘healthy driver’ effect whereby drivers with a medical condition may recognise that they are not able to fully control a car and may either cease driving or restrict their driving. Their opportunity to be in a crash is therefore reduced, and this contributes to a lower crash risk than may otherwise be expected.
• The definition and incidence of crashes when driving often depends on self- reporting, which may lead to over- or under- reporting in some studies.
• The definition of a ‘medical condition’ is by self-report in some studies and may not be accurate.
• The ‘exposure metric’ (i.e. kilometres travelled) is often not controlled for, yet is crucial for determining the risk of a crash.
• Sample sizes may be small and not represent the general population of drivers.
• The control group may not be properly matched by age and sex.
• Commercial drivers are rarely considered as a separate cohort, and generalisations based on evidence from private motor vehicle drivers may not be appropriate.
• Studies rarely identify whether and how drivers are treated/untreated – for example, corrected vision for those with vision impairments and hearing aids for those with hearing impairments.
• Comorbidities may not be adjusted for (e.g. alcohol dependence).

The implications are that false-negative results may occur whereby the condition appears to have no effect or minimal effect on driving safety. The authors acknowledge that care should be taken in interpreting the literature and that professional opinion plus other relevant data should be taken into account in determining the risks posed by medical conditions. The authors also note that the review focused on published peer-reviewed literature. There was no inclusion of technical reports, conference presentations or abstracts, case studies, coroner reports or studies, cohort studies (without a control group) or reviews of consensus-based medical standards for any of the medical conditions reviewed.

For the purposes of this publication the term ‘crash’ refers to a collision between two or more vehicles, or any other accident or incident involving a vehicle in which a person or animal is killed or injured, or property is damaged.

Health professionals should also keep themselves up to date with changes in medical knowledge and technology that may influence their assessment of drivers, and with legislation that may affect the duties of the health professional or the patient.