All That's Trucking

Marijuana and Truck Driving Don't Mix

March 4, 2013

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No matter what you believe about the safety of marijuana, it's still illegal for interstate truck drivers.
No matter what you believe about the safety of marijuana, it's still illegal for interstate truck drivers.
So how bad is smoking marijuana for you, anyway? Well, if you're a truck driver, it's very dangerous to your license and livelihood. 

In last November’s election, voters in Washington and Colorado made it legal to possess an ounce of pot and use it for recreation. And Massachusetts joined the 17 other states (and the District of Columbia) that allow medical marijuana.

But marijuana is illegal under federal law, and its use is expressly forbidden for transportation workers, including truck and bus drivers.

(And a number of states have zero-tolerance laws for driving with any evidence of pot in your blood.)

Toke up and Drive?

Shortly after we reported on Truckinginfo in late January that the DOT was warning truck drivers about not making the mistake of smoking marijuana just because their home state might allow it, we got a long email from a reader who took issue with the government's position on this issue. He included lots of examples of research. 

For instance, this lawyer's blog talked about research showing that those driving while high drove more slowly and were less likely to change lanes, he said. However, the same article noted that there's also evidence of "performance changes in braking latency," (which I understand to mean a slower reaction time when it's time to hit the brakes) and also some evidence of impairment of peripheral vision.

Plus, it says, Canadian researchers recently concluded that smoking pot within three hours of driving nearly doubles the risk of a vehicle collision.

My personal take? Even if driving under the influence of pot is less dangerous than driving while drunk, that still doesn't necessarily mean it's actually safe! 

In Your Blood

In addition, new research appears to show that you could be under the influence of marijuana for far longer than after drinking.

The research, published online last week in Clinical Chemistry, the journal of AACC, shows that cannabis (marijuana) can be detected in the blood of daily smokers for a month after last intake. The researchers hope the data could help promote "drugged driving" laws, saying marijuana is second only to alcohol for causing impaired driving and motor vehicle accidents.

In 2009, 12.8% of young adults reported driving under the influence of illicit drugs and in the 2007 National Roadside Survey, more drivers tested positive for drugs than for alcohol. These cannabis smokers had a 10-fold increase in car crash injury compared with infrequent or nonusers after adjustment for blood alcohol concentration, according to the paper.

In this paper, 30 male chronic daily cannabis smokers resided on a secure research unit for up to 33 days, with daily blood collection. Twenty-seven of 30 participants were THC-positive on admission. THC decreased gradually with only 1 of 11 participants negative at 26 days; two of the five remained THC-positive for 30 days.

These results demonstrate, for the first time, that cannabinoids can be detected in blood of chronic daily cannabis smokers during a month of sustained abstinence. 

However, there doesn't seem to be agreement as to whether THC in your blood actually means you're impaired. A 2007 study found that a THC concentration of 10 nanograms/mililiter — a level sufficient to prove DUI in several states — is not associated with elevated accident risk. 

Of course, this is all strictly academic, so to speak. No matter what various studies say, federal law says you can't smoke pot and drive a commercial vehicle.


  1. 1. Krymsun [ March 03, 2013 @ 09:51PM ]

    Per Se Drugged Driving Laws and Traffic Fatalities
    D. Mark Anderson - Montana State University
    Daniel I. Rees - University of Colorado Denver

    Per Se Drugged Driving Laws and Traffic Fatalities

    The Office of National Drug Control Policy (ONDCP) recently announced a goal of reducing drugged driving by 10 percent within three years. In an effort to achieve this goal, ONDCP is encouraging all states to adopt per se drugged driving laws, which make it illegal to operate a motor vehicle with a controlled substance in the system. To date, 16 states have passed per se drugged driving laws, yet little is known about their effectiveness. The current study examines the relationship between these laws and traffic fatalities, the leading cause of death among Americans ages 5 through 34. Our results provide no evidence that per se drugged driving laws reduce traffic fatalities.

    Our results suggest that per se laws are negatively related to traffic fatalities in the cross section. Controlling for unobserved heterogeneity at the state level, the estimated relationship between per se laws and traffic fatalities becomes positive, but is statistically indistinguishable from zero. We conclude that, as currently implemented, making it illegal to operate a motor vehicle with drugs (or drug metabolites) in the system, has no discernible impact on traffic fatalities.

  2. 2. Krymsun [ March 03, 2013 @ 09:52PM ]

    Please read

  3. 3. Matt McL [ March 04, 2013 @ 08:04PM ]

    I got my Class 'A' license stoned. Blame California if you don't want stoned truck drivers. Michigan and many other states recently disqualified metabolites(urine test) as an indicator of impairment.

  4. 4. ThisGuy [ April 19, 2013 @ 11:09PM ]

    It's either marijuana or xanax for me. I can not drive with xanax, but I drive fine with marijuana. I use it as needed, but I honestly don't trust myself with xanax. This is all a bunch of assuming by people who have no understanding of how marijuana works

  5. 5. Eric Byers [ February 07, 2015 @ 08:36PM ]

    If you fail a drug screen. Even if it has been 30 day, 60 days or whatever, you can kiss you career goodbye. 10 year blackball and even then it will be hard to find work. I know, personal experience.

  6. 6. Califorina life style [ November 18, 2015 @ 01:43PM ]

    Be smart don't start getting paid 10 a hour is not going to work think before you blew


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Deborah Lockridge

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All That's Trucking blog is just that – the editor's take on anything and everything related to trucking, with the help of guest posts from other HDT editors. Author Deborah Lockridge's career as an award-winning trucking journalist started in 1990.


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