What impairment rates for drivers in fatal crashes were lowest for?

Impairment rates for drivers in fatal crashes were lowest for those under the influence of alcohol compared to other substances like opioids or stimulants. While alcohol remains a significant factor in many fatal accidents, the rates of impairment linked to drugs such as marijuana and prescription medications have been increasing. Additionally, studies indicate that drivers without any detectable impairments tend to have the lowest fatal crash rates overall.