Drug Impaired Driving
Every state has laws dealing with alcohol-impaired driving and drug-impaired driving. But unlike the laws for drunk driving, those that address drugged driving are nuanced, difficult to enforce and prosecute and vary substantially by state.
In addition to general impairment laws, there are two basic laws that states tend to use when addressing drug-impaired driving:
- Zero Tolerance laws make it illegal to drive with any measurable amount of specified drugs in the body. These laws are best suited for illegal drugs: if it is illegal to possess or use a drug, then it is reasonable to prohibit driving after the drug has been possessed and used.
- 16 states have zero tolerance laws in effect for one or more drugs.
- Per Se laws make it illegal to drive with amounts of specified drugs in the body that exceed set limits.
- 5 states have per se laws in effect for one or more drugs.
Marijuana Drug-Impaired Driving Laws
18 states have zero tolerance or non-zero per se laws for marijuana.
- 10 states have zero tolerance for THC or a metabolite.
- 4 states have zero tolerance for THC but no restriction on metabolites.
- 4 states have specific per se limits for THC
- 1 state (Colorado) has a permissible inference law for THC
NOTE: GHSA does not compile any additional data on drug-impaired driving laws other than what is presented here. A compilation of state marijuana laws is available via the Insurance Institute for Highway Safety, and information on marijuana-impaired driving laws is available from the National Alliance to Stop Impaired Driving (NASID). For more information, consult the appropriate State Highway Safety Office.
Sources: State Highway Safety Offices.
Last updated in January 2024. Laws last reviewed by SHSOs in March 2023.
Per se >0 for some drugs
Decriminalized and legal for recreational and medical use
THC per se (5 ng)
Per se >0 for some drugs
Decriminalized and legal for medical use
THC per se (2 ng)
Per se >0 for some drugs
Legal for medical use
THC per se (5 ng)
Permissible inference law >0 for THC
Decriminalized and legal for recreational and medical use
Permissible inference for THC (5 ng)
None
Decriminalized and legal for recreational and medical use
None
None
Decriminalized and legal for recreational and medical use
None
None
Decriminalized and legal for medical use
None
None
None
Legal for medical use
None
Decriminalized and legal for medical use
None
None
Decriminalized
None
None
None
Decriminalized and legal for medical use
None
Legal for medical use
Decriminalized
Decriminalized and legal for medical and recreational use
None
None
None
Decriminalized and legal for medical and recreational use
None
None
Decriminalized and legal for medical use
None
None
Decriminalized and legal for medical and recreational use
None
None
Decriminalized and legal for medical and recreational use
None
Zero tolerance for some drugs
Illegal
Zero tolerance for delta-9-THC
Zero tolerance for some drugs
Legal for medical use
Zero tolerance for THC and metabolites
Zero tolerance for some drugs
Illegal
Zero tolerance for THC and metabolites
Zero tolerance for some drugs
Decriminalized and legal for medical use
Zero tolerance for THC and metabolites
Zero tolerance for some drugs
Legal for medical use
Zero tolerance for THC and metabolites
Zero tolerance for some drugs
Legal for medical use
Zero tolerance for THC and metabolites
None
Zero tolerance for some drugs
Decriminalized
Zero tolerance for some drugs
Decriminalized and legal for medical and recreational (effective 8/1/23) use
Zero tolerance for THC but no restriction on metabolites (effective 8/1/23)
Zero tolerance for some drugs
Legal for medical and recreational use
Zero tolerance for THC
Zero tolerance for some drugs
Illegal
None
Zero tolerance for some drugs
Illegal
Zero tolerance for THC
Illegal
Zero tolerance for THC and metabolites
Zero tolerance for some drugs
Zero tolerance for some drugs
Decriminalized and legal for recreational and medical use
THC per se (5 ng)
Zero tolerance for some drugs
Illegal
Zero tolerance for THC and metabolites
Zero tolerance for some drugs
Decriminalized and legal for medical use
Zero tolerance for THC and metabolites
Zero tolerance for some drugs
Legal for medical use
Zero tolerance for THC and metabolites
None
Illegal
None
None
Illegal
None
None
Illegal
None
None
Decriminalized for legal for medical use
None
None
Decriminalized and legal for medical use
None
None
Illegal
None
None
None
Illegal
None
Legal for medical use
None
None
Legal for medical use
None
None
Illegal
None
None
Decriminalized and legal for recreational and medical use
Decriminalized and legal for recreational and medical use
None
None
None
None
Legal for medical use
Decriminalized and legal for medical and recreational use
None
None
Per se >0 for some drugs
Decriminalized and legal for medical and recreational use
THC per se (2 ng) for felony violations
None
Decriminalized and legal for medical use
None
None
None
Illegal
Decriminalized and legal for recreational and medical use
None
None
Per se >0 for some drugs
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