Transportation Bill Would Set Federal Cannabis Impairment Standard

The federal government has no standardized way to measure whether a driver is impaired by marijuana. A bipartisan transportation bill released this week by House committee leaders would require federal officials to study the problem and develop “evidence-based impairment standards” for cannabis and other drugs — a formal attempt to close a gap that rescheduling has only made harder to ignore.

Representatives Sam Graves (R-MO) and Rick Larsen (D-WA) — chair and ranking member of the House Transportation and Infrastructure Committee — released the text of the BUILD America 250 Act on May 17, 2026. The bill covers surface transportation broadly — roads, bridges, rail, motor carrier safety — but its provisions on marijuana and drug impairment address one of the more pressing policy tensions in federal transportation law.

What the Bill Would Require

The cannabis provision sits within the bill’s highway safety research framework. Under the bill, the transportation secretary would be required to carry out a collaborative research effort examining how marijuana and polysubstance use affects driving ability, identifying ways to reduce drug-impaired driving, and proposing evidence-based impairment standards for marijuana and polysubstance use. The National Highway Traffic Safety Administration would separately be directed to report to Congress on the status of ongoing collaborative research to advance impaired driving prevention technology.

The mandate matters because no such federal standard currently exists. The testing framework for safety-sensitive transportation workers — truck drivers, airline pilots, train engineers, ship captains, and others — detects the presence of marijuana metabolites in urine, not actual impairment. A driver can test positive days after last use, long after any impairment has passed. Existing tests cannot reliably differentiate between someone who consumed marijuana last week and someone impaired behind the wheel today.

A separate provision would create a national drug-involved crash data collection system, directed to gather standardized toxicology data from states for fatal and serious injury crashes, link crash records with hospital and emergency services data, and establish model protocols for specimen collection and reporting. The Department of Transportation could award grants to states to support pilot programs, toxicology labs, and training. All collected data would be deidentified before public release.

The Rescheduling Gap This Bill Would Address

The timing is deliberate. On April 23, 2026, the Drug Enforcement Administration rescheduled FDA-approved marijuana products and state-licensed medical marijuana products from the most restrictive federal drug category to a less restrictive one — a significant shift under the Trump administration. But the rescheduling order addressed drug classification, not safety testing. It said nothing about how DOT should treat its existing testing obligations or how impairment should be evaluated for workers operating vehicles and aircraft.

The Department of Transportation responded by holding the line: safety-sensitive transportation workers still cannot use medical marijuana without violating federal rules. The department’s Office of Drug and Alcohol Policy and Compliance has maintained that marijuana remains incompatible with safety-sensitive functions — and that changing the drug’s federal classification does not change the legal basis for DOT’s testing authority or the zero-tolerance testing framework the department has long operated under. Medical review officers reviewing a positive test result cannot accept a state medical marijuana authorization as a valid explanation; the federal testing procedures explicitly exclude it.

What’s missing is the science underneath the policy. No validated standard currently exists for what constitutes marijuana impairment in a vehicle operator. Courts, state regulators, and federal agencies have all worked around that absence rather than through it. The BUILD America 250 Act would direct the federal government to close that gap — not by changing who gets tested or lowering tolerance thresholds, but by producing the scientific grounding that any durable impairment standard will eventually require.

What Comes Next

Committee leaders plan to formally introduce the legislation soon; a markup date has not been announced. The current surface transportation authorization expires on September 30, 2026, setting a hard deadline for action.

Graves called the bill “the most important surface transportation bill since President Eisenhower built the Interstate Highway System,” citing its bridge investment (BRDG ) and infrastructure reforms. Larsen, the committee’s Democratic lead, acknowledged the bill required compromise: “A commitment to bipartisan lawmaking means finding compromise; while this bill does not include every priority, I am committed to building on the last bipartisan infrastructure law.”

If enacted, the mandate to study and codify marijuana impairment standards would represent the first time a federal transportation reauthorization has formally directed the government to resolve what has been an open and increasingly inconvenient scientific question — one that rescheduling has brought into sharper focus without answering.