The NCSL Blog


By Annie Kitch

The holidays are often a time of celebration when we give ourselves permission to indulge in our favorite holiday treats. However, these festivities often include alcohol and other impairing substances, making the holidays one of the most dangerous seasons on our roads.

Woman in car using ignition interlock deviceAn average of 300 people died annually since 2013 in drunk-driving crashes during the week between Christmas and New Year’s Eve according to the National Highway Traffic Safety Administration. A total of 781 people lost their lives in drunk-driving-related crashes in December 2016 alone. 

NHTSA’s 2013-2014 National Roadside Survey shows that 20 percent of nighttime weekend drivers tested positive for drugs. The proportion of marijuana-positive drivers involved in fatal crashes increased from 8 percent in 2013 to 17 percent in 2014, according to the AAA Foundation for Traffic Safety. However, there is not a definitive answer for why the number of marijuana-positive drivers increased.

December is National Impaired Driving Prevention Month, a campaign that highlights the consequences of impaired driving and reminds all drivers that like drunk driving, drugged driving is impaired driving.

Lawmakers and enforcement officials are uniting under this message year-round to enact and toughen laws and enforcement related to impaired driving. Although every state has a law that addresses alcohol and drug-impaired driving, those that deal with drug impairment are difficult to enforce due to uncertainty over how to best determine impairment.

Drivers can benefit from understanding state laws and penalties pertaining to impaired-driving before getting behind the wheel. Get a glimpse of state alcohol and drugged driving laws below:

State Alcohol-Impaired Driving Laws: 

  • Every state except Utah has established a legal blood alcohol concentration (BAC) limit of .08 percent. Effective Dec. 30, Utah’s BAC will be set at a level of 0.05 percent. 
  • A total of 29 states require the use of an ignition interlock device (IID) for all first time DUI offenders. Idaho and Iowa most recently enacted an all-offender ignition interlock law in 2018. 
  • Arizona toughened its IID legislation in 2018 by extending the length of time an IID must be installed if a driver fails to pass three consecutive IID tests during a drive cycle.  
  • A handful of states require subsequent DUI offenders to participate in treatment and sobriety monitoring programs such as a 24/7 sobriety monitoring program. Since 2017, Delaware, Hawaii, Iowa, Michigan, South Dakota, Utah and Washington have enacted laws concerning 24/7 sobriety monitoring.  
  • The most common methods for testing BAC are through blood, breath and urine samples. 

State Drugged-Driving Laws: 

  • Thirty-one states, the District of Columbia, Guam and Puerto Rico now allow for comprehensive public medical marijuana and cannabis programs. Ten states—California, Colorado, Hawaii, Massachusetts, Maine, Michigan, Nevada, Oregon, Vermont and Washington—and Washington, D.C., permit recreational marijuana use.
  • Thirty-two states require a driver to be visibly impaired by THC to receive a driving under the influence of drugs (DUID) citation; 12 states have a zero-tolerance law that prohibits driving with any amount of THC and/or its metabolites in the body; and five states have established a per se limit that prohibits driving with a detectable amount of THC in the body that exceeds the legal limit. Colorado has a permissible inference law that applies if THC is identified in a driver’s blood in quantities of 5ng/ml or higher.
  • In 2017, Colorado passed a law requiring that DUI and DUID cases involving drugs, alcohol or a combination of both be reported to the state legislature for data analysis.
  • Currently, the most common methods to detect marijuana are through blood, urine or saliva. Michigan administered an oral fluid roadside drug testing pilot program in five state counties from November 2017 to November 2018. During the pilot, a Drug Enforcement Officer was permitted to require a person to submit a roadside oral fluid test to detect whether they were driving under the influence of drugs. The results of the pilot will be used to frame the state’s law around roadside drug testing to determine a driver’s impairment. 

Annie Kitch is a transportation research analyst II in NCSL’s Transportation Program.

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This blog offers updates on the National Conference of State Legislatures' research and training, the latest on federalism and the state legislative institution, and posts about state legislators and legislative staff. The blog is edited by NCSL staff and written primarily by NCSL's experts on public policy and the state legislative institution.