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SELECT A STATE from the National Totals dropdown menu to view statistics about impaired driving and underage drinking.

SELECT A LAW to view the details of each state’s impaired driving and underage drinking laws.

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State Law: DUID Affirmative Defense
  • Affirmative defense
  • No affirmative defense
  • Special circumstances

In every state in the country, it is illegal to drive while impaired by drugs. Some states have zero tolerance (ZT) or per se DUID laws that make it illegal for a person to drive with certain drugs (or more than a specified amount of certain drugs) in their system. The laws operate similarly to the nation’s 0.08 BAC laws for alcohol. However, they typically afford drugged drivers an absolute “affirmative defense” essentially exempting those who take medications pursuant to a valid prescription. The defense applies to the ZT and per se provisions only; it does not apply to the traditional DUI provisions. The rationale for this is simple. First, drivers should not be entitled to drive while impaired by any substance, regardless of its legality. Thus, just as a driver with a blood alcohol level below 0.08 is guilty of DUI if they drive impaired, a driver with a valid prescription for a drug is guilty of DUI if they drive while impaired. Second, doctors cannot authorize a person to drive while impaired by giving them a prescription.

The following chart contains links to the current affirmative defense statutes.

For more information about drug-impaired driving laws and enforcement, please refer to this resource. To learn more about the drug-impaired driving laws in your state, visit our DUID map and our marijuana-impaired driving map.

To submit a law update, please contact out Director of Traffic Safety at [email protected]


2016 Alcohol-Impaired Driving Fatality Data Montana National
Total Alcohol-Impaired Driving Fatalities 85 10,497
Percent of Alcohol-Impaired Driving Fatalities of Total Fatalities 44.7 28.0
Under 21 Alcohol-Impaired Driving Fatalities 8 1,031
Percent of Under 21 Alcohol-Impaired Driving Fatalities of Total Under 21 Fatalities 33.3 22.3
2016 Alcohol-Impaired Driving Fatalities per 100,000 Population
Alcohol-Impaired Driving Fatalities per 100K population 8.2 3.3
Under 21 Alcohol-Impaired Driving Fatalities per 100K population 3.0 1.2
2007-2016 % Change in Alcohol-Impaired Driving Fatalities per 100K Pop
10-year Change in Alcohol-Impaired Driving Fatalities per 100K pop -26.2 -24.7
10-year Change in Under 21 Alcohol-Impaired Driving Fatalities per 100K pop -44.7 -44.8
Percent of Alcohol-Impaired Driving Fatalities Involving high BAC drivers (.15+)*
BAC=.15+ 80.6 70.3
Percent of Drivers in Fatal Crashes Involving Repeat Offenders
BAC .08-.14 12.5 26.6
BAC .15+ 87.5 73.4
12-20 Year Old Alcohol Consumption (latest available)
Past Month Alcohol Consumption (2015-2016) 22.0 19.8
Binge Drinking in Past 30-days (2015-2016) 15.4 12.7
2016 Arrest Data
Under 18: Driving under the influence 42 5,135
Total: Driving under the influence 4,392 1,017,808
Under 18: Liquor laws 454 29,073
Total: Liquor laws 1,871 234,899
Under 18: Drunkenness 0 3,805
Total: Drunkenness 0 376,433

Alcohol-Impaired Driving Fatality Data Source: NHTSA/FARS, 10/17

*Among drivers with a known alcohol test result

Youth Consumption Data Source: SAMHSA, Office of Applied Studies, National Surveys on Drug Use and Health, 12/2017 (

Arrest Data Source: 2016 FBI Uniform Crime Report (Tables 18, 20 and 22)

**Drunkenness is not considered a crime in some states; therefore, the figures may vary widely from state to state

Limited, incomplete, or no data were reported by the District of Columbia, Florida, Illinois, and New York in the 2016 Uniform Crime Report. Data should be used with caution and should not be compared to other states or previous year data.

Note: Because the number of agencies submitting arrest data varies from year to year, users are cautioned about making direct comparisons between 2016 arrest totals and those published in previous years’ editions of Crime in the United States. Further, arrest figures may vary widely from state to state because some Part II crimes of the Uniform Crime Report are not considered crimes in some states.

For a comprehensive report on 2016 (latest available) State of Drunk Driving Fatalities in America, click here.

State Law State Law Detail
24/7 Programs Statewide program
Administrative License Suspension/Revocation No ALS/ALR law
BAC Test Refusal Administrative penalties
Drug Evaluation and Classification Program 51-100 DREs
DUI Child Endangerment Laws Enhanced penalties
DUI Look-back Periods Lifetime
DUID Zero Tolerance and Per Se Laws Per se limit greater than zero for some drugs
Enhanced Penalties for High-BAC 0.16
Felony DUI Fourth offense
Good Samaritan Good Samaritan law enacted
Habitual Offender Designation Habitual Offender Law Enacted
Marijuana Drug-Impaired Driving Laws THC per se (5 nanograms)
Open Container - Alcohol In compliance with Federal requirements
Sobriety Checkpoints Alternative to checkpoints
DUID Affirmative Defense No affirmative defense
DUI Courts - Standalone 1-5 DUI Courts
DUI Courts - Hybrid 1-5 Hybrid Courts
Open Container - Marijuana No marijuana open container law
Ignition Interlocks Discretionary