Photo: Lindsay Fox, CC BY 2.0, via Wikimedia Commons
No. Driving while impaired by cannabis is illegal in every US state and DC, including states where recreational marijuana is legal. The same goes for prescription and over-the-counter medicines that affect your driving. This guide covers how drug-impaired driving laws work, what is allowed in the car, and the penalties.
Key facts
- Driving impaired by any substance is illegal in all 50 states and DC (NHTSA).
- NHTSA says marijuana can slow your reaction time, impair your judgment of distance and reduce coordination.
- There is no single national THC limit like the 0.08 alcohol limit. Each state writes its own drug-impaired driving law.
- Prescriptions are no defense if the drug impairs you. California’s handbook says the law does not distinguish illegal drugs from medicines from a doctor or pharmacy.
- Implied consent covers drug tests too. In California, refusing a blood or urine test when an officer suspects impairment leads to a 1-year suspension or revocation.
Can you drive after smoking weed?
Not while you are impaired, and you cannot measure that yourself. Unlike alcohol, there is no reliable “wait X hours” rule. Effects vary with the product, the dose and the person. The practical rule: if you have used cannabis, do not drive. Get a ride, use a ride-share, or wait until the next day.
How police and courts decide you were impaired
- Your driving and behavior: weaving, slow reactions, and what the officer observes at the stop.
- Chemical tests: blood, urine or saliva tests can detect drugs that a breath test cannot. New York lists breath, blood, urine and saliva tests.
- State law: some states set a legal drug limit, others rely on proof of impairment. Check your state handbook’s alcohol and drugs chapter.
Cannabis in the car: what is allowed
Rules on carrying cannabis are separate from impaired driving. California and New York as examples:
| Rule | California | New York |
|---|---|---|
| Smoking or eating cannabis while driving | Illegal for the driver and passengers (except in buses, taxis, campers and motorhomes) | A traffic infraction for a driver or passenger to consume cannabis in a vehicle on a public road |
| Carrying cannabis | Container must be sealed and unopened, or kept in the trunk or a place where passengers do not sit | Check the DMV manual and state law |
| Penalty for consuming in the vehicle | Check the DMV handbook | First conviction: fine up to $150, plus a surcharge and fee, and possibly up to 15 days in jail |
Penalties for drug-impaired driving: New York example
| First offense of DWAI-drug | New York |
|---|---|
| Classification | Misdemeanor |
| Fine | $500 to $1,000 |
| Jail | Up to 1 year |
| License | Suspended for at least 6 months |
| Under 21 | Any alcohol or drug driving conviction: revoked for at least 1 year |
Other states set their own penalties. See implied consent and DUI in the US.
Medicines and mixing substances
- Read labels for warnings about drowsiness or operating machinery. New York’s manual notes that a cold remedy can affect you as much as several drinks.
- Ask a pharmacist or doctor how a new medicine affects driving before you drive on it.
- Alcohol plus other drugs, cannabis included, is especially dangerous. New York’s manual says the combination severely reduces your ability to drive.
Common questions
Is it legal to drive high if weed is legal in my state?
No. Legal to buy is not legal to drive on. Impaired driving is illegal everywhere.
Can I refuse a drug test?
You can refuse, but implied consent penalties apply. In California, refusing a blood or urine test leads to a 1-year suspension or revocation.
Is a medical marijuana card a defense?
No. The impaired driving laws still apply. California’s handbook says the law does not see a difference between illegal drugs and medications, and it is illegal to drive after taking any drug that affects your driving.
Can my passenger smoke in the car?
Not in California or New York, except in vehicles such as buses and taxis in California, or vehicles like stretch limousines in New York. Other states have their own rules.
What happens to a teen’s license for drug driving?
Expect the harshest penalties. New York revokes for at least 1 year for drivers under 21. A drug or alcohol offense can also delay your next GDL stage. See zero tolerance laws for drivers under 21.
Can I take cannabis across state lines?
Cannabis laws differ from state to state. Check the law of every state you will drive through before you carry anything.
Related: points systems and license suspensions, car insurance for new drivers, learning to drive in the USA.
Sources
- National Highway Traffic Safety Administration, “Drug-Impaired Driving” and “Understanding How Marijuana Affects Driving” (nhtsa.gov)
- California DMV, “California Driver’s Handbook, Section 9: Alcohol and Drugs” (dmv.ca.gov)
- New York DMV, “Driver’s Manual, Chapter 9: Alcohol and Other Drugs” and “Penalties for Alcohol or Drug-Related Violations” (dmv.ny.gov)