Utah's 0.05% BAC Limit Linked to 9% Fewer Alcohol-Involved Crashes

Utah's decision to set its drunken-driving threshold at 0.05% blood alcohol concentration was followed by a sustained decline in alcohol-involved crashes, not just a one-year dip, according to a study the Insurance Institute for Highway Safety released October 27. The percentage of crashes that involved alcohol fell about 9% after the law took effect on December 30, 2018, and stayed lower through four full years of data.

Utah remains the only state with a 0.05% per se limit. Every other state prosecutes impaired driving at 0.08%, a threshold that became universal in 2005 only after the Department of Transportation tied federal highway money to it. The National Transportation Safety Board recommended the lower limit in 2013, citing immediate drops in fatal collisions in other industrialized countries that adopted it. No state legislature has followed Utah since.

What four years of crash records added

The earlier evaluation of Utah's law looked at a single year and depended on police reports of alcohol involvement, a measure that misses cases where a blood test comes back later or where a driver refuses to provide a sample. IIHS senior research scientist Angela Eichelberger and independent researcher Scott Tippetts widened the definition, counting crashes as alcohol-involved when a positive test result was appended to the report afterward and when a driver declined testing.

They also tracked single-vehicle nighttime crashes, a standard proxy for alcohol involvement, and ran the same calculations on Arizona, Idaho and Colorado as comparison states.

The results diverged by measure. Crash records reclassified with the broader alcohol definition showed the decline; single-vehicle nighttime crashes, the proxy, did not produce a conclusive signal. Injury crashes involving alcohol fell 12%. And relative to the three neighboring states, whose alcohol-involvement rates climbed over the same period, Utah's share of crashes involving alcohol dropped somewhere between 12% and 21%.

A state that is unusually hard to measure

Utah starts from one of the lowest alcohol-involved crash rates in the country, partly because a large share of residents abstain for religious reasons. A small base is difficult to move, which cuts both ways: the same feature that makes an effect hard to detect also suggests the law could produce a bigger change elsewhere.

Two other complications shaped the design. Lawmakers passed the 0.05% limit more than a year before it took effect, with heavy publicity, so the researchers analyzed the passage-to-implementation window separately rather than attributing everything to the effective date. And the COVID-19 pandemic landed in the middle of the study period. During the March–May 2020 lockdown, alcohol-involved crashes in Utah jumped 46%; averaged across the entire 34-month pandemic, the monthly share of crashes involving alcohol rose 6%. Strip those years out and the estimated reduction gets larger, though it loses statistical significance because so much data goes with them.

The paper's own abstract is careful about the limit of what it proves: "The uniqueness of the alcohol environment in Utah and the confounding effects of the pandemic prevent us from determining the size of the effect." What it does claim is that the law "had continued benefit, both independently and in contrast to neighboring states," which is a narrower statement than a precise national estimate and more useful than the single-year snapshot it replaces.

The argument the number supports

IIHS President David Harkey framed the finding as a policy signal rather than a settled estimate. "Crash risk increases with the amount of alcohol in your system, but it spikes noticeably at 0.05%," he said. "A lower limit is grounded in science and also sends a message that buzzed driving is drunk driving."

Harkey put the stakes at more than 10,000 deaths a year in alcohol-related crashes nationwide, a toll he said justifies "every tool we have, including stricter BAC limits." That framing is likely to surface in statehouses that have considered — and so far declined — similar bills, where opponents have argued that a 0.05% standard would criminalize responsible behavior and burden the courts without changing the behavior of drivers who are already well above the limit.

The Utah data does not settle that argument, and the study's authors say so. What it does establish is that the law's effect did not fade after its first year, which was the central open question when the earlier evaluation appeared.

Where treatment fits

A lower legal threshold changes the consequences of a night of drinking for a driver who is stopped. It does nothing for the person who cannot stop drinking, the population most likely to be arrested repeatedly under any limit. Screening at the point of arrest and in emergency departments remains the main channel into care for alcohol use disorder, and the options that follow are more varied than they were a decade ago: medically supervised withdrawal at detoxification programs, outpatient counseling, and medications including naltrexone, which reduces heavy drinking in some patients.

Few of those pathways are funded at the scale of the problem. Utah's crash statistics describe what happens on the road; the alcohol addiction caseload behind them is where the state's treatment capacity, not its traffic code, becomes the binding constraint.