An interlock device in every new car 'could prevent 80% of drunk

Nov 02, 2023

Every day, almost 30 people in the US lose their lives in an alcohol-related motor vehicle crash. But according to a new study, introducing alcohol interlock devices to all new motor vehicles could prevent more than 80% of these deaths.

According to the Centers for Disease Control and Prevention (CDC), 10,322 people in the US were killed in alcohol-related motor vehicle crashes in 2012, accounting for more than 30% of all motor vehicle deaths.

More than 1,100 of these deaths involved children aged 14 and under, and 20% of these cases involved a driver who was under the influence of alcohol.

In most US states, people who are convicted of driving a motor vehicle while under the influence of alcohol are often required to get an alcohol interlock device, also known as an ignition interlock device, installed in their vehicle in order to prevent them from further engaging in drunk driving.

An ignition interlock device is a mechanism installed in a vehicle's dashboard. It works like a breathalyzer, in that the driver must breathe into the device for it to measure their blood alcohol content (BAC). If the driver's BAC is above the legal limit – which varies by state – the vehicle will not start.

"Interlocks are highly effective while installed on the vehicle," note the researchers, including Dr. Patrick Carter of the University of Michigan Injury Center, "with a systematic review finding a 67% median reduction in DWI (driving while intoxicated) recidivism."

For their study, the results of which are published in the American Journal of Public Health, Dr. Carter and colleagues set out to estimate how many alcohol-related motor vehicle injuries and fatalities could be avoided over the next 15 years if interlock devices were installed in all new vehicles.

Using data from the Fatality Analysis Reporting System and the National Automotive Sampling System's General Estimates System, the team assessed the nonfatal injuries and fatalities that occurred as a result of alcohol-related motor vehicle crashes between 2006 and 2010.

The researchers then estimated the effect universal installation of interlock devices in all newly built vehicles would have on nonfatal injuries and fatalities over the next 15 years, as well as the effect it would have on injury-related costs.

The study results suggest that 85% of alcohol-related motor vehicle deaths and 84-88% of nonfatal injuries in the US could be prevented over a 15-year period through installation of interlock devices in all new vehicles. This equates to 59,554 lives saved and around 1.25 million nonfatal alcohol-related vehicle crashes prevented, according to the researchers.

The team estimated that universal installation of interlock devices for drivers aged 21-29 – who are considered to be at highest risk for alcohol-related motor vehicle crashes – would pose the greatest benefit, accounting for around 35% of all prevented deaths and nonfatal injuries.

What is more, the researchers found that introducing interlock devices to all newly built vehicles would save around $343 billion in unintentional injury costs over a 15-year period. While it would cost around $400 to install each device, the researchers estimate that the cost savings to society would outweigh the cost of device installation within 3 years.

Talking to Medical News Today about the results, Dr. Carter said:

"We knew our modeling would yield significant results, but the sheer numbers of preventable fatalities and serious injuries were surprising.

Our analysis clearly demonstrates the significant public health benefit and societal cost savings associated with including alcohol ignition interlock devices as standard equipment in all new cars."

The team's findings are subject to some limitations. Dr. Carter told us that the team's estimates were based on an interlock device being installed in every new vehicle and the alcohol limit of the device being set to 0.02 grams per deciliter (g/dL). Currently, some devices are set up to 0.04 g/dL.

"While the standard use of alcohol interlocks in all new vehicles is one solution for the prevention of drinking and driving, policy makers, car manufacturers and the public will need to best determine how such technology can best be optimally deployed," Dr. Carter told MNT. "Our research does demonstrate the potential opportunity for injury prevention and cost savings with widespread use throughout all vehicles."