Abstract
Most traffic accidents may be attributed to driver impairment as a consequence of factors such as inattention, fatigue, intoxication, etc. It is now technically feasible to monitor and diagnose driver behaviour with respect to impairment with the aid of a limited number of in-vehicle sensors, however, a valid framework for the evaluation of driver impairment is still lacking. In order to provide an acceptable definition of driver impairment, a method is needed to assess both absolute and relative criteria. The seemingly paradoxical goal is to develop a definition of impaired driving that is consistent, yet adaptable to inter-individual differences.