State laws requiring ignition interlocks for all drunk driving offenders appear to reduce the number of fatal drunk driving crashes, a new study by the Johns Hopkins Bloomberg School of Public Health and Colorado School of Public Health researchers suggests.
The study — published Jan. 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 with at least one driver with 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 is an alcohol-sensing device, connected to the ignition of a vehicle, which detects alcohol in the driver’s breath. If alcohol in excess of a preset limit is detected by the sensor, 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.