Lower BAC Limits

Laboratory studies show impairment in driving ability begins at levels below .08 g/dL BAC (i.e., Moskowitz et al., 2000). The National Transportation Safety Board (2013) is one organization that has recommended a BAC of .05 g/dL or lower for all drivers. Consequently, many countries, and some U.S. jurisdictions, impose penalties for drivers who have BACs of .05 g/dL or higher. From a recent survey, 53% of drivers in the United States supported lowering the BAC limit for all drivers from .08 to .05 g/dL (AAAFTS, 2021).

All States have BAC limits of .02 g/dL or lower for drivers under 21 (NIAAA, 2022a). These laws reinforce MLDA laws prohibiting people under 21 from purchasing or possessing alcohol in public. Additionally, some States set BAC limits of .02 or .04 g/dL for people convicted of DWI, to emphasize that they should not be driving after drinking.

Use:

All States have an illegal per se BAC limit of .08 g/dL with the exception of Utah, which enacted a .05 g/dL law that went into effect on December 30, 2018. Colorado and New York both have driving while ability impaired laws (impairment at a BAC lower than .08 g/dL) and West Virginia may revoke a license at a BAC above .05 g/dL. As of November 2016 four States, Nebraska, North Carolina, Vermont, and Virginia, have lower BAC limits for people convicted of DWI (NCSL, 2016a).

Effectiveness:

A NHTSA study evaluated the impact of Utah’s .05 g/dL per se law (Thomas et al., 2022). The study showed reductions in fatal crashes and overall numbers of people killed in 2019 (the first year the .05 law was in effect) compared to 2016 (the last full year before the law was passed). In 2019, despite increased VMT Utah recorded 225 fatal crashes and 248 fatalities, which is lower than the 259 fatal crashes and 281 fatalities for 2016. When VMT is considered, the fatal crash rate reduction from 2016 to 2019 in Utah was 19.8%, and the fatality rate reduction was 18.3%. In com­parison the rest of the United States showed a 5.6% fatal crash rate reduction and 5.9% fatality rate reduction during the same time. Neighboring Arizona, Colorado, and Nevada did not show the same levels of improvement in fatal crash and fatality rates as Utah. In telephone surveys conducted of the general public in Utah, there was increased awareness for the .05 limit among drinkers, After the BAC limit was lowered, some drinkers reported making sure alternative transportation was available when drinking away from home. As there is sometimes concern that a lower limit will negatively affect a State’s hospitality industry, the study examined alcohol sales. These sales in Utah from 2012 to 2018 increased, and the trend continued through Fiscal Year 2020, after the law was in effect. Similar patterns were observed for sales tax revenues from restaurants, rental car, hotel, and resort sales, as well as air travel to Utah and visitors to State and National parks.

Evaluations from other countries suggest lower BAC limits reduce alcohol-impaired driving and crashes (NHTSA, 2003). For example, a law introduced in British Columbia, Canada, in 2010 included an administrative 3-day license suspension and possible vehicle impoundment for drivers with BACs from .05 to .08 g/dL. The law was intended to maximize deterrence by increasing the certainty and swiftness of sanctions. In the year after the law took effect, there was a 40% decrease in alcohol-related fatal crashes (Macdonald et al., 2013). Moreover, roadside surveys revealed a 44% decrease in drivers with BACs of .05 g/dL or higher, and a 59% decrease in drivers with BACs over .08 g/dL (Beirness & Beasley, 2014). In 2008 Brazil lowered the BAC limit from .06 g/dL to .02 g/dL for all motorists. Violations result in suspensions of driving privileges. Roadside surveys conducted before and after the law change found a 45% decrease in drivers with a positive BAC (Campos et al., 2013).

Not all jurisdictions that have lowered their BAC limits have seen subsequent reductions in crashes. For example, in 2014 Scotland lowered the BAC limit for all drivers from .08 g/dL to .05 g/dL. Although alcohol consumption in bars and restaurants decreased, there was no change in traffic crashes, injuries, or fatalities (Haghpanahan et al., 2019). The researchers noted that no special enforcement took place after the BAC limit was lowered. In sum, the available evidence suggests lowering the illegal per se limit to .05 g/dL for all drivers can reduce alcohol-related crashes and fatalities, but publicizing and enforcing the lower BAC limit may be important.

Several studies have also examined lower BAC limits specifically for DWI offenders. In 1988 Maine established a .05 g/dL BAC limit for 1 year after a first DWI offense and for 10 years after a subsequent offense. Violators received an administrative license suspension. In 1995 this BAC limit was further lowered to .00 g/dL. Hingson et al. (1998) evaluated the 1988 law and concluded that it reduced the proportion of fatal crashes that involved repeat offenders by 25%. Jones and Rodriguez-Iglesias (2004) evaluated the overall effects of both laws, using data from 1988 to 2001. They also concluded that the laws contributed to a reduction in the proportion of repeat offenders in fatal crashes, primarily due to a reduction in drivers at BACs of .10 g/dL and higher.

Costs:

Implementation and operation costs are minimal. Jones and Rodriguez-Iglesias (2004) found that Maine’s laws had little or no cost effect on the operations of the DWI control system. Overall, the burden on the court system will be lessened if penalties are administrative, rather than criminal (as was the case in British Columbia).

Time to implement:

Lower BAC limit laws can be implemented as soon as legislation is enacted.