The prevalence and nature of stopped on-the-road driving tests and the relationship with objective performance impairment

► The decision to stop a driving test is a subjective one, that depends on the awareness of performance impairment and risk perception by either the driver or the instructor. ► The decision to stop a driving test is made after both treatment with CNS-drugs and placebo. ► Tests that are stopped can have 'normal' SDLP values, while tests with higher SDLP values may be completed. ► SDLP is a poor correlate of the decision to stop a driving test.