WSLH Toxicology: Alcohol Intoxication

Alcohol is a central nervous system depressant. It acts upon the brain where it depresses nerve transmission and impedes the coordination between nerve centers in the brain. The effect of this depressant action is to impair normal mental and physical faculties. Although the effects of alcohol are widely known to the public, its effects on driving are often misconstrued. Driving is a complex, divided-attention task. Drivers must maintain a safe speed, safe spacing between vehicles on the road, lane control, and so forth while being alert for unexpected hazards.

Much research on the effects of alcohol on driving ability has been conducted over the years. The studies fall into three major categories:

• Alcohol effect on driving-related tasks.
• Alcohol effect measured using driving simulators and closed-course driving.
• Epidemiological studies of the incidence of alcohol involvement in motor vehicle crashes.

Alcohol has been found to affect the following driving-related areas:

• Judgement, risk assessment and self-evaluation
• Reaction time, especially in divided attention tasks
• Muscular coordination
• Vision and visual acuity

The effect of alcohol on the above mental and physical faculties combines to cause impairment of driving skills.

The consensus in the scientific community upon review of these studies is that alcohol causes measurable impairment of driving and driving-related skills at virtually any alcohol concentration that can be detected. All drivers are impaired at alcohol concentrations* of 0.08 and above. Some drivers are significantly impaired at alcohol concentrations below 0.08.

*Alcohol concentrations in this paper are in g/100 mL for blood or g/210 L for breath.