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Driving under the influence isn’t just about alcohol anymore. These days, more people are being charged with driving while high on marijuana. Whether you use cannabis regularly or just once in a while, it’s important to know the laws. This guide explains how marijuana DUI laws work, how police check for impairment, and what to do if you’re ever charged.
A marijuana DUI happens when someone drives a car while high on cannabis. Unlike alcohol, where the rules are based on your blood alcohol level (BAC), marijuana is harder to measure. THC—the part of marijuana that makes you feel high—can stay in your body for days or even weeks. This means someone might test positive even if they’re not currently impaired, making it more difficult to tell if a person is actually too high to drive.
As more states allow medical and recreational marijuana, more people are using cannabis legally. According to the National Highway Traffic Safety Administration (NHTSA), more drivers are testing positive for marijuana, especially at night on weekends. Some may not even realize they’re still affected. Because of this, police are paying closer attention and cracking down on marijuana-impaired driving.
| Key fact | Source |
|---|---|
| THC can remain detectable hours to days after impairment ends, so sober regular users can still test positive. |
[1] |
| IIHS found collision claims 2-6 % higher in early-legal states versus controls. | [2] |
| Colorado roadway deaths with ≥ 5 ng THC rose from 56 (2019) to 101 (2022) before dipping to 87 (2023). |
[3] |
| Washington lists cannabis as the second-most common drug in fatal crashes; 75 % of THC-positive drivers also carried alcohol/other drugs. |
[4] |
For insurers these trends translate into higher personal-auto loss costs, new underwriting
surcharges, and rising demand for legal-expense products.
| State (legal since) |
DUI THC rule | 2023-24 highlights |
|---|---|---|
| Alaska (2015) | Effect-based (observation + lab) | DRE staffing doubled; saliva pilot slated 2026. |
| Arizona (2021) | Effect-based (zero-tolerance repealed) | 2 240 drug-DUI arrests 2024; 28 % cannabis-related. |
| California (2018) | Effect-based; no numeric limit | $100 m Prop 64 grants fund DUI blitz & training. [5] |
| Colorado (2014) | Permissible inference ≥ 5 ng | THC fatals 101 → 87; “Meet the Effects” media push. [3] |
| Connecticut (2021) | Effect-based; per-se study under way | 2024 law funds roadside oral-fluid pilot. |
| Delaware (2023) | Zero-tolerance (any THC) | Task force weighing 2 ng or 5 ng limit. |
| Illinois (2020) | Per-se 5 ng/mL blood [6] | Cannabis present in 31 % of fatal drug tests 2023. |
| Maine (2017) | Effect-based | Legislature debating 5 ng limit; AAA opposes. |
| Maryland (2023) | Effect-based | 150 new DRE officers funded ahead of July 2025 retail launch. |
| Massachusetts (2016) | Effect-based | “Shifting Gears” impairment module required in all driving schools. [7] |
| Michigan (2018) | Effect-based; statewide oral-fluid pilot since 2019 | 661 roadside saliva tests; program extended to 2025. [8] |
| Minnesota (2023) | Effect-based | First statewide saliva-analyzer pilot (2024) under evaluation. [9] |
| Missouri (2023) | Effect-based | Drug-DUI arrests up 19 % YoY; 90 more DREs funded. |
| Montana (2021) | Per-se 5 ng | THC in 25 % of fatals; 3 ng limit proposal pending. |
| Nevada (2017) | Per-se 2 ng [10] | Statewide SoToxa rollout planned 2025. |
| New Jersey (2021) | Effect-based; drug-influence eval required after crashes | 2024 AG directive adds 4-hour blood-draw warrant rule. |
| New Mexico (2021) | Effect-based | Task force to fund 10 000 DRE training hours. |
| New York (2021) | Effect-based | Breathalyzer field trials with SUNY; results late 2025. |
| Ohio (2023) | Per-se 2 ng blood [11] | $7 m allocated to DRE & lab backlog as sales begin. |
| Oregon (2015) | Effect-based | Case-control crash study under way; saliva bill stalled. |
| Rhode Island (2022) | Zero-tolerance | “Cannabis DUI = $5 000 Fine” signage on I-95. |
| Vermont (2018) | Effect-based | 2024 law authorises VR eye-tracking impairment test. |
| Virginia (2021) | Effect-based | DUI arrests ↑ 13 % 2023→24 despite retail delay. |
| Washington (2012) | Per-se 5 ng | THC present in 33 % of 2023 fatals; 44 % poly-drug. [4] |
| Tech | Status (May 2025) | Insurance Implication |
|---|---|---|
| Saliva analyzers (SoToxa, Draeger) |
Pilots in MN, AL, IN, MI, CO, WI. | Faster roadside confirmation could cut wrongful arrests → smaller need for defense cover. |
| THC breathalyzers (Hound Labs) |
First commercial units to employers 2024; law-enforcement pilots late 2025. | If breath tests pinpoint <4 h impairment, insurers may bundle DUI defense with telematics. |
| VR / cognitive-impairment tests | Field trials in VT, IL, MO. | Long-term option for mixed-drug impairment; standards still years out. |
Nicole Bill is a Commercial Insurance Specialist at Cover Cannabis. A graduate from Humboldt State University with a Bachelors of Science in Business Administration. Nicole began her professional career in Banking and Investments, helping people invest for their retirement through Life Insurance and Annuities. Nicole was drawn to the insurance space because she saw an opportunity of growth and help business owners through the confusing aspects of insurance, specifically in the Cannabis industry.
On her time off, Nicole enjoys playing with her kids and gardening.