5.1.1 Effects of musculoskeletal conditions on driving
A motor vehicle driver must be able to execute and coordinate many complex muscular movements in order to control the vehicle (refer to Figure 12). They must have an adequate range of movement, sensation, coordination and power of the upper and lower limbs. Generally speaking, the upper extremities are needed to steer, shift gears and operate secondary vehicle controls (e.g. the indicators and horn). The lower extremities are required to operate the clutch, brake and accelerator pedals. The ability to rotate the head is particularly important to permit scanning of the environment including when reversing.
Chronic impairment of the musculoskeletal system may arise from numerous disorders and trauma (e.g. amputations, arthritis, ankylosis, deformities and chronic lower back pain) resulting in limited range of movement or reduced sensation, balance, coordination or power. Issues related to muscle tone, spasm, sitting tolerance and endurance, as well as the effects of medications such as long-term opioid- based analgesics, may also need to be considered (refer to Part A section 2.2.8 Drugs and driving).
It is possible to drive safely with quite severe impairment; however, driver insight into functional limitations, stability of the condition and compensatory body movements or vehicle devices to overcome deficits are usually required. Adaptive equipment can be installed in many vehicles (e.g. hand-operated brake and accelerator, automatic transmission and height-adjustable seats) that enable many drivers with impairments to operate vehicles safely (refer to Table 6).
It should be noted that vehicles, especially commercial vehicles, vary considerably in terms of cabin design, vehicle controls and ergonomics. The needs of motorcyclists also differ due to the type of controls and the overall driving task, as well as requirements for balance and agility. Given this variability in requirements, the medical standards are based on functionality with respect to the particular vehicle and driving task rather than specific requirements in terms of range of movement.