Effects of alcohol impairment on motorcycle riding skills

Alcohol intoxication is a significant risk factor for fatal traffic crashes; however, there is sparse research on the impairing effects of alcohol on skills involved in motorcycle control. Twenty-four male motorcycle riders between the ages of 21 and 50 were assessed on a test track with task scenarios based on the Motorcycle Safety Foundation's (MSF) training program. A balanced incomplete block design was used to remove confounding artifacts (learning effects) by randomizing four BAC levels across three test days. In general, intoxicated riders demonstrated longer response times and adopted larger tolerances leading to more task performance errors. Most of the alcohol effects were evident at the per se 0.08% alcohol level, but some of the effects were observed at the lower 0.05% alcohol level. The effects of alcohol on motorcycle control and rider behavior were modest and occurred when task demand was high (offset weave), time pressure was high (hazard avoidance for near obstacles), and tolerances were constrained (circuit track). The modest effects may be due to the study design, in which experienced riders performed highly practiced, low-speed tasks; alcohol at these levels may produce larger effects with less experienced riders in more challenging situations.