1.5 Development and evidence base
A key input in terms of evidence for the licensing criteria remains the Monash University Accident Research Centre (MUARC) report Influence of chronic illness on crash involvement of motor vehicle drivers, 2nd edition.1 This is an update of the original 2004 report and provides a comprehensive review of published studies involving domestic drivers in Western countries between May 2003 and June 2009. It investigates the influence of chronic illness and impairments on driving performance and crash involvement, including condition prevalence, evidence of crash involvement and other measures of driver risk.
In compiling this report, MUARC sought the best available evidence but acknowledges the quality of evidence is variable. In interpreting the research, there is therefore a need to consider a number of sources of potential bias including:
- 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 ‘exposure metric’ (i.e. kilometres travelled) is often not controlled for, yet is crucial for determining the risk of a crash.
- The definition of a ‘medical condition’ is by self-report in some studies and may not be accurate.
- Sample sizes may be small and not representative of the population of drivers.
- The control group may not be properly matched by age and sex.
- Comorbidities may not be adjusted for, for example, 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.
While the current review has not involved a further systematic review of the literature, input has been secured for the current edition of Assessing Fitness to Drive through the involvement of several expert groups and through the review of coronial cases. Where recent evidence has become available to inform refinement of licensing criteria, this has been included in the revised chapters.
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.
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.