The Guidelines

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Road Safety Audit

8.4 Dynamics

The auditor must be alert to the implications of motorcycles’ unique dynamics which are key to optimising motorcyclists’ safety. A non-motorcyclist might suppose that “motorcycles accelerate faster than cars and can avoid traffic queues.” Whilst this is true, auditors need to be aware of other serious yet subtle differences when balancing risks.  It should always be foremost in an auditor’s mind that a ‘low risk, low severity’ hazard to a twin-track driver may present ‘a low risk, high severity’ hazard to a motorcyclist.

Most of the important dynamic differences between motorcycles and other vehicles arise from the way motorcycles use the ‘laws of physics’. For example, no other motor vehicles have wheels that can, and indeed must, move significantly out of the vertical to enable manoeuvres such as cornering.  At speed, the wheels behave like two large gyroscopes, adding a further dimension to their physical properties.  A skilful rider can make good use of this gyroscopic effect. A novice may experience unexpected effects. For example, on bends, applying the front brake can cause the machine to ‘sit up’ and take a line tangential to the bend. Predictable and consistent bend geometry is therefore critical to rider safety. Those involved in providing or maintaining the road infrastructure must understand that a motorcycle is by no means a ‘fast bicycle’ or a ‘two-wheeled car’.