What are the most common reasons why drivers have impaired judgment?

Alcohol and fatigue are the most common reasons why drivers have impaired judgment.

Alcohol

At least 15,000 car journeys per day are made by drivers under the influence of alcohol, and about 20-30% of all drivers killed in traffic accidents have alcohol in their blood.

Fatigue

Research shows that as many as 20% of all traffic accidents are caused by fatigue (tiredness). The most common type of traffic accidents due to fatigue are single-car accidents. 40% of all single-car accidents happen in darkness or at dawn, and many of these are likely due to fatigue.