Utah's 0.05% BAC limit linked to nearly 9% drop in alcohol-related crashes, IIHS study finds
Utah, the first and still only U.S. state to set a 0.05% blood alcohol limit, saw a nearly 9% reduction in alcohol-related crashes over the four years after its law took effect, a new IIHS study shows.
- 0.05%
- 0.08%
- Nearly 9%
- More than 10,000
What Happened
Utah became the first U.S. state to lower the blood alcohol concentration threshold for impaired driving to 0.05% from 0.08% when its law went into effect on Dec. 30, 2018, and it remains the only one. A new study from the Insurance Institute for Highway Safety finds the stricter limit was associated with a nearly 9% reduction in alcohol-related crashes over the next four years. The percentage of crashes involving alcohol dipped when the 0.05% per se law was passed and dropped a further 9% when it took effect, relative to the previous several years. IIHS says the long-term drop held up across several supporting analyses.
U.S. states widely adopt per se laws, initially with limits set as high as 0.15% and remaining at 0.10% in many states for quite some time.
A 0.08% BAC limit becomes universal after the Department of Transportation makes it a requirement for receiving certain federal highway funds.
The National Transportation Safety Board recommends that states lower their limits to 0.05%.
Utah's 0.05% per se law goes into effect, the first in the United States.
Alcohol-involved crashes in Utah spike 46% during the COVID-19 lockdown, a dramatic but fleeting increase.
Nearly 9%
Reduction in Utah's share of crashes involving alcohol over the four years after the 0.05% law took effect.
IIHS Senior Research Scientist Angela Eichelberger and independent researcher Scott Tippetts analyzed the first four years of crash data. Unlike an earlier study that relied on police reports of alcohol involvement, the new one also counted crashes where alcohol-positive test results were added to the report later and crashes where the driver refused a BAC test. The researchers additionally tracked single-vehicle nighttime crashes, which can serve as a proxy for alcohol involvement, and compared Utah's alcohol-involved crash rates before and after the law with rates in Arizona, Idaho and Colorado.
- Down nearly 9% after implementation
- Down 12%
- Down 12%-21%
- Utah has always had one of the lowest rates of alcohol-involved crashes in the U.S. because many residents abstain from alcohol for religious reasons — which the researchers could not account for.
- The law passed with great fanfare more than a year before it was implemented, so publicity may have changed behavior beforehand; researchers examined that gap period separately.
- The COVID-19 pandemic, which drove nationwide spikes in alcohol use and drinking and driving, occurred midway through the study period; results were checked with and without those months.
- Because Utah's baseline was relatively low, the researchers note a 0.05% law might have a smaller effect elsewhere — or an even larger one, since a low base makes the needle harder to move.
“These encouraging results from Utah should make other states take note. More than 10,000 people lose their lives in alcohol-related crashes every year in the U.S. We need to use every tool we have, including stricter BAC limits, to reduce that toll.”
Why this matters
Utah is the only U.S. state with a 0.05% BAC limit, and this four-year study addresses what an earlier one-year look left unclear: whether the lower threshold actually reduces alcohol-involved crashes. The finding matters for lawmakers in other states, which the National Transportation Safety Board urged in 2013 to drop to 0.05%, and for Utah drivers, in a country where more than 10,000 people die in alcohol-related crashes each year.
Terms in This Story
- BAC
- Blood alcohol concentration — the share of alcohol in a person's bloodstream, used as the legal measure of impairment.
- per se law
- A law that makes it a crime to drive with a blood alcohol concentration above a set limit, even if the driver does not appear to be intoxicated.
- single-vehicle nighttime crashes
- Crashes involving one vehicle at night; researchers often use counts of them as a proxy for alcohol involvement.
- statistically significant
- A result is statistically significant when it is unlikely to be explained by chance alone.
Summarised from the linked release; details can be imperfect — always verify against the original source.