The Merits of Adopting a 0.05 Administrative Blood Alcohol Concentration Limit for Driving

One way to reduce alcohol-impaired driving fatalities and injuries is to lower the criminal blood alcohol concentration (BAC) limit for driving from 0.08 to 0.05 grams per deciliter. There is sound rationale behind this measure. Most industrialized countries—except for the United States—have enacted a 0.05 BAC limit. In Canada, however, most provinces have enacted administrative rather than criminal laws that penalize drivers with BACs ranging from 0.05 to 0.08 grams per deciliter with a short-term loss of the offender’s drivers’ license, a fine, and possibly vehicle impoundment. Studies in Canada show significant declines of alcohol-related crashes associated with the adoption of the 0.05 administrative law. It should be easier to convince US state legislatures to adopt administrative sanctions for drivers with a BAC of 0.05 to 0.08, where the sanctions are not as severe and the law serves to get a dangerous driver off the road. Once implemented in some states, it should be possible to evaluate the effectiveness of these administrative laws in reducing impaired driving crashes in the United States, following the lead of the Canadian studies.

Several prominent public health organizations (e.g., World Health Organization, American Medical Association) have policies supporting a BAC of 0.05 or lower as the illegal limit per se for drivers aged 21 years and older. Most countries, including the United States, have a zero tolerance limit of BAC ≥ .02 g/dL for drivers under the minimum legal drinking age. At least 91 countries around the world have adopted a 0.05 or lower BAC limit for driving while 54 countries use BAC limits from 0.06 to 0.12.¹

Laboratory and test track research shows that the vast majority of drivers, even experienced drinkers who typically reach a BAC of 0.15 or greater, are impaired at a BAC of 0.05 or higher with regard to critical driving tasks.² Some studies report that performance decrements in some of these tasks are as high as 30% to 50% at a BAC of 0.05.

The risk of being involved in a crash increases significantly starting at a BAC of 0.05.³ The risk of being involved in a crash increases at each 0.01 increase in BAC level, but rises very rapidly after a driver reaches or exceeds a BAC of 0.05 compared with drivers with no alcohol in their blood system (BAC = 0.00).

Lowering the illegal BAC limit to 0.05 is a proven effective countermeasure that has reduced alcohol-related traffic fatalities in other countries, most notably Australia. While studies in Europe and Australia each use a different methodology to evaluate these effects, the evidence is consistent and persuasive that fatal and injury crashes involving drinking drivers decrease on the order of at least 5% and up to 18% after a country lowers their illegal BAC limit from 0.08 to 0.05.⁴ If all states were to adopt and enforce the 0.05 BAC standard, an estimated 500 to 800 lives could be saved each year.⁵

A BAC of 0.05 is a reasonable standard to set. The National Highway Traffic Safety Administration surveys show that most people would not drive after consuming two or three drinks in an hour and believe the limit should be no higher than the BAC level associated with that.⁶ That would be a BAC of 0.05 or lower for most drivers.

Progress in reducing impaired driving has stalled over the past 15 years. Lowering the BAC limit from 0.08 to 0.05 can potentially serve as a general deterrent to all those who drink and drive, and sends a message that the state is getting tougher on impaired driving and will not tolerate it. Such legislation typically reduces drinking drivers in fatal crashes at all BAC levels (> 0.01, > 0.05, > 0.08, > 0.15). A review of the evidence for a 0.05 BAC law was recently published.⁷

To date, no state has adopted a 0.05 BAC criminal per se statute in the United States. However, in Canada, except for Quebec, all provinces have enacted administrative laws that penalize drivers with BACs ranging from 0.05 to 0.08. Canada has a federal criminal law set at 0.08, similar to the United States. In the province of British Columbia, this administrative law is called Immediate Roadside Prohibition or IRP and requires a three-day license suspension, a $200 fine, and possibly a three-day vehicle impoundment for a first offense. Studies show that this administrative 0.05 BAC limit is effective.

One study of the British Columbia law found significant decreases in fatal crashes (21%), in hospital admissions (8.0%), and in ambulance calls for road trauma (7.2%) associated with the implementation of the 0.05 BAC administrative law.⁸

Administrative license suspension has proven to be much more effective than criminal suspension.⁵ Provisions for the law could include administrative penalties for a first offense at a BAC of 0.05 to 0.08 and criminal sanctions for repeat 0.05 offenses. Currently, there is significant legislative action in the United States concerning distracted driving. Perhaps a 0.05 BAC administrative amendment could be attached to these bills.

There is little doubt that a 0.05 BAC limit would generate sufficient controversy to capture and reinvigorate public attention. The implementation of 0.08 BAC limits in the 1980s and 1990s in the United States resulted not only in a reduction in the percentage of fatally injured drivers with a BAC at that level but also at a BAC of 0.20 or greater. Lower BAC laws are also associated with reductions in alcohol consumption in states that adopt them. Administrative license suspension gives police an option for dealing with drivers at a BAC below the current 0.08 BAC criminal limit.

It is recommended that the United States adopt legislation providing for administrative 0.05 BAC programs similar to the IRP programs in Canada. These administrative BAC laws may be more palatable to state legislatures. Once implemented in a couple of states, it will be possible to evaluate the effectiveness of such programs in reducing impaired driving crashes.