Table of Contents

2.2.1 Conditions likely to affect driving

Given the many causal factors in motor vehicle crashes, the extent to which medical conditions contribute to vehicle crashes is difficult to assess.

There is, however, recognition of the potential for certain conditions to cause serious impairments. Examples of such conditions include:

  • blackouts
  • cardiovascular disease
  • diabetes
  • musculoskeletal conditions
  • neurological conditions such as epilepsy, dementia and cognitive impairment due to other causes
  • psychiatric conditions
  • substance misuse/dependency
  • sleep disorders
  • vision problems.

These conditions may affect sensory, cognitive or motor function, or a combination of these.

Impairments associated with medical conditions may be persistent (e.g. visual impairment) or episodic (e.g. seizure). Drivers with persistent impairments can be assessed based on observations and measures of their functional capacity. Those with episodic impairment must be assessed based on a risk analysis that takes into account the probability and consequence of the episode.

Treatments for medical conditions (including drug treatments and others) can also affect driving ability through effects on cognition and reaction time (refer to section 2.2.8 Drugs and driving).

Drivers may present to treating health professionals with a range of conditions. Some may affect driving temporarily or may affect the patient’s ability to drive at some time in the future; others might be complicated by the presence of multiple conditions. The content of this publication focuses on common conditions known to affect fitness to drive and in particular on determining the risk of a patient’s involvement in a serious vehicle crash caused by loss of control of the vehicle.