State laws requiring ignition interlocks for all drunk driving offenders appear to reduce the number of fatal drunk driving crashes, according to a new study by the Johns Hopkins Bloomberg School of Public Health and Colorado School of Public Health.
The study, which was published January 5 in the American Journal of Preventive Medicine, found that mandatory interlock laws were associated with a seven percent decrease in the rate of fatal crashes where at least one driver has a blood alcohol content over the legal limit. The decrease translates into an estimated 1,250 prevented fatal crashes in states with mandatory interlock laws since states first started passing such laws in 1993.
An ignition interlock connects to the ignition of a vehicle and detects alcohol in a driver’s breath. If the sensor detects alcohol in excess of a preset limit, the vehicle will not start. While all 50 states have some type of ignition interlock laws, 26 have mandatory laws requiring all individuals convicted of a DUI offense to use an interlock in order to drive legally, as of March 2016.
This is the first study to look at all the different types of interlock laws across all 50 states. The researchers found that interlock laws which are mandatory for all DUI offenders were much more effective than those applicable to only some offenders, such as only repeat offenders or those with a very high blood alcohol content.
In the United States in 2014, alcohol-involved fatal motor vehicle crashes caused approximately 10,000 deaths, about one-third of all motor vehicle crash deaths.
“Our study demonstrates the value of mandatory ignition interlock laws across the United States,” said study leader Emma E. “Beth” McGinty, PhD, MS, deputy director at the Johns Hopkins Center for Mental Health and Addiction Policy Research at the Bloomberg School. “We already know that alcohol plays a tragic role in the number of motor vehicle crash fatalities each year. Interlock laws which are mandatory for all DUI offenders save lives.”
McGinty added: “Until recently, there hasn’t been any evidence on whether these laws prevent alcohol-involved fatal crashes, and specifically whether mandatory/all laws are more effective than permissive and partial laws. Our study suggests that they are effective, and it’s encouraging to see more and more states moving towards this evidence-based policy change. Since 2005, we’ve seen over 20 states adopt interlock laws for all drunk-driving offenses. We’d like to see the remaining states follow suit.”
“Ignition Interlock Laws: Effects on Fatal Motor Vehicle Crashes, 1982–2013” was written by Emma E. McGinty, PhD, MS; Gregory Tung, PhD, MPH,; Juliana Shulman-Laniel, MPH; Rose Hardy, MPH; Lainie Rutkow, JD, PhD, MPH; Shannon Frattaroli, PhD, MPH; and Jon S. Vernick, JD, MPH.
Click here to open the research article (external site PDF).
The study was supported by the Centers for Disease Control and Prevention.