So say many experts who have studied the U.S. (including California’s) DUI limit of 0.08 percent. The only state that has a lower limit is Utah, which has a 0.05 percent per se limit.
After Utah lowered it limit in 2018, there was a near 20 percent decrease in fatal car crashes according to the National Highway Traffic Safety Administration. Although this decrease in fatal car crashes in Utah continues to be widely reported, The Salt Lake Tribune reports that this trend seen from 2018 and 2019 may have been short-lived. There has been a slight upward trend in Utah road fatalities since, but this may be attributable to a number of factors—then again, so might the decrease seen in 2018 and 2019.
Nevertheless, there is evidence also that some Utah drivers have adjusted their behavior since the enactment of the lower DUI limit. In a focus group conducted by the Utah Department of Public Safety, 22 percent of drivers who drink said they now look for alternative ways to get home after drinking, rather than driving themselves.
Orange County DUI Lawyer Blog

