IIHS: Utah’s Strict Alcohol Limit Linked to Lasting Drop in Crashes

Utah’s lower legal blood alcohol concentration limit for drivers was associated with reduction in alcohol-related crashes over four years, according to a new study from the Insurance Institute for Highway Safety.

For the four years after the state lowered the limit to 0.05% Utah saw a nearly 9% reduction in alcohol-related crashes, according to an IIHS study.

Utah became the first state to lower its BAC threshold for impaired driving from 0.08% to 0.05% in 2018. It remains the only state with the lower limit.

IIHS researchers analyzed crash data from the first four years after the change and compared Utah’s alcohol-involved crash rates with those in Arizona, Colorado and Idaho.

Relative to the years before the law took effect, the share of Utah crashes involving alcohol fell further after implementation of the 0.05% limit. The percentage of injury crashes involving alcohol declined 12%, according to the study.

The share of crashes involving alcohol in Utah fell 12% to 21%, while alcohol-involvement rates increased in the comparison states, compared with Arizona, Colorado and Idaho, the study shows.

Researchers also accounted for the COVID-19 pandemic, which was accompanied by an increase in alcohol use and impaired driving nationwide. Alcohol-involved crashes in Utah rose 46% from March through May 2020, but the increase was short-lived. Over the 34-month pandemic period studied, the average monthly share of crashes involving alcohol increased 6%.

According to IIHS researchers, Utah presents some challenges for comparison because the state historically has had one of the nation’s lowest rates of alcohol-involved crashes. The law also received substantial publicity more than a year before it took effect, which researchers say may have influenced driver behavior before implementation.

The 0.08% limit became universal in 2005 after the federal government tied certain highway funding to adoption of that standard.

The National Transportation Safety Board recommended in 2013 that states lower BAC limits to 0.05%, citing impairment in depth perception and reaction time at that level.