The DOT, Drug Testing, and the Changing Marijuana Landscape

Two color modern semi truck and trailer in winter wether

Marijuana and the Federal Law

The Federal Motor Carrier Safety Administration (FMCSA) regulates truck driver use and testing for marijuana and other drugs.  Federal drug testing includes mixtures and synthetic versions.  The testing protocols and procedures are set out in the Code of Federal Regulations (CFR) –

As every CDL holder should know, drivers can be tested in the following circumstances:

  • Pre-employment screening
  • Post-accident (when a fatality, injury or vehicle tow-away is involved)
  • Random testing
  • Reasonable suspicion
  • Return-to-duty and follow-up, following a positive test

In each of these instances, the test will reveal if there is the presence of marijuana.  If the level is above the regulated cutoff points, the driver will legally have failed the drug test, irrespective of whether the driver was “inebriated” at the time the test samples were taken.

On the horizon at the FMCSA is the Commercial Driver’s License Drug & Alcohol Clearinghouse.  The launch is expected in early 2020, the clearinghouse will contain the results of federal drug tests for five years or after a driver completes a return-to-duty test, whichever is later.  Motor carriers will be able to query the clearinghouse to see whether a potential hire has a record of positive tests.  Click on the following link for more information regarding the Clearinghouse –

What are the Different Classes of Drugs for Drug Tests?

DOT drug tests require laboratory testing for the following five classes of drugs:

  • Marijuana
  • Cocaine
  • Opiates – opium and codeine derivatives
  • Amphetamines and methamphetamines
  • Phencyclidine – PCP

Marijuana is still considered a Schedule 1 drug by the federal government.  Federal law always overrules state and local laws.  If you test positive for THC, this is a legal nightmare for trucking companies.  If you smoke marijuana while off-duty, and not drive while under the influence, you can still test positive for THC for up to 30 days.  Due to DOT regulations, failing a single drug test is grounds for termination.  It does not matter if it is legal in that state and you consumed marijuana while off duty.  The DOT is a federal agency and they have a zero-tolerance policy.

What are the Effects of Marijuana?

Studies have clearly demonstrated that marijuana does impair recognition and physical reactions needed for safe driving:

  • Attention: Safe driving requires the reception, distinguishing and prioritization of numerous stimuli – from road signs to other drivers to pavement conditions.  It reduces the ability of drivers to juggle more than one thing at once.
  • Reaction: Being “mellow” may limit a driver’s sense of aggravation, but it also slows reaction times.
  • Lane position: A driver’s ability to steadily control the vehicle is impaired by marijuana intoxication.  This is often seen by movement within a lane.  A marijuana-intoxicated driver may attempt to compensate for his slower reactions and impaired control by increasing his following distance from other vehicles.

While standard roadside field sobriety tests are used for alcohol, such testing is not evidence of active impairment or intoxication for marijuana due to the body’s mechanisms for processing THC.  Unlike alcohol, THC in blood tests are not reliable indicators of driver impairment.  The National Highway Transportation Safety Administration offers evidence that some state laws allow an individual to be charged with a DUI if they test positive for THC derivatives in urine following arrest, which indicates marijuana use in past 30 days but not necessarily recent marijuana use.

Federal funds are being used to educate prosecutors and judges on drug-impaired driving cases, efforts to prosecute drug-impaired driving have been met with numerous setbacks.

How have the Laws Regarding Marijuana Changed?

Laws regarding marijuana have changed drastically in the last 5 to 6 years. Only five states maintain an outright prohibition on marijuana possession and use.  Those states are Alabama, Idaho, Kansas, Nebraska and South Dakota.With 31 states legalizing medical marijuana, 10 states plus DC legalizing recreational use, nationwide legalization in Canada (recreational use) and Mexico (medical use), marijuana-induced driving under the influence (DUI) is a growing safety concern.

Despite a changing landscape nationally regarding the legality of marijuana use and questions regarding employment-based drug tests, there’s little that’s changed for the trucking industry.  Truck drivers must still test negative for use of marijuana and fleets must maintain a drug testing program.  Regardless of state laws, commercial drivers still fall under federal government guidelines.  Even in states where marijuana is considered legal, it is still illegal to drive while impaired by any substance.  No matter how the federal laws might change, there will still be strict regulations in place by the DOT to keep impaired drivers from getting behind the wheel of a commercial vehicle.  It is not just drivers either, as it is illegal to transport marijuana in planes or any other form of transportation.  These laws do make it difficult for medical marijuana users who have verified medical ailments which marijuana has been proven to treat.

Considering all the strict regulations and laws, it is unlikely that the DOT or trucking companies will ever relent, no matter how mainstream the use of marijuana becomes.  It is a liability issue for truck drivers and trucking companies and will most likely remain federally prohibited for some time.


Fleetowner, April 4, 2019 “Increasing Marijuana Legalization and Use Raises Concerns For Trucking”, Steve Vaughn.

TrucknewsJJ, May 9,2019, “Fleets Must Maintain Drug Testing Regimen Despite Changing Marijuana Landscape”, James Jaillet.