Study: Per Se Drugged Driving Laws Have Little Or No Impact On Traffic Deaths

  • by Paul Armentano, NORML Deputy Director January 14, 2013

    The imposition of so-called per se drugged driving laws, which create new traffic safety violations for drivers who operate a vehicle with the presence of trace amounts of certain controlled substances and/or their inert metabolites (byproducts) in their blood or urine, do not reduce incidences of traffic safety deaths.

    That’s the conclusion of a just-published study by economists at the University of Colorado, Denver and Montana State University. The study is available from the Institute for the Study of Labor (IZA) in Germany as a Discussion Paper.

    Since 1990, 11 states have passed so-called zero-tolerant per se drugged driving laws which make it illegal for one to drive with detectable levels of a controlled substance in his or her system. Five additional states have passed similar laws specifying non-zero limits for controlled substances or their metabolites. Fourteen (Arizona, Delaware, Georgia, Illinois, Indiana, Iowa, Michigan, Nevada, Ohio, Pennsylvania, Rhode Island, Utah, Washington, and Wisconsin) of these sixteen states impose these strict liability per se standards for cannabis. Recently, the White House Office of National Drug Control has recommended zero tolerant per se drug standards for all US states.

    Using state-level data from the Fatality Analysis Reporting System (FARS) for the period 1990-2010, authors examined the relationship between the adoption of controlled substance per se thresholds and overall incidences of traffic fatalities. They found that the relationship is statistically indistinguishable from zero and concluded that there is no evidence that these limits reduced traffic deaths.

    Authors reported: “Despite the fact that these laws have been touted by politicians and academics as an effective strategy for making our roadways safer, we find no evidence that they reduce traffic fatalities. … [W]e cannot determine why per se drugged driving laws do not work, and leave this issue to future researchers. However, our results clearly indicate that, as currently implemented, laws that make it illegal to drive with detectable levels of a controlled substance in the system have little to no effect on traffic fatalities.”

    In November, Washington state voters approved Initiative 502, which legalizes the private use and retail sale of cannabis to adults, but also imposes a 5ng/ml THC/blood per se limit for drivers over the age of 21. In Colorado, where voters on Election Day similarly legalized cannabis, Democrat Gov. John Hickenlooper and Republican Senator Steven King are calling for the passage of nearly identical per se cannabis legislation.

    NORML has consistently opposed the imposition of stand-alone per se limits for cannabinoids, arguing that the presence of THC in blood, particularly at lower levels, is an inconsistent predictor of behavioral impairment, particularly in more frequent consumers who may potentially test positive for trace, residual THC levels in their blood for periods of time exceeding any period of acute impairment.

    Operation of a motor vehicle while under the influence of cannabis is already a criminal offense in all 50 states. However, in order for one to gain a criminal conviction under most state DUI laws, prosecutors must prove that a motorist recently ingested cannabis and that doing so prohibited him or her from driving safely.

    Full text of the study, “Per Se Drugged Driving Laws and Traffic Fatalities,” is available online here. A separate paper previously published by the same authors reported that the passage of statewide medical marijuana laws is associated with decreased incidences of traffic fatalities.

    38 responses to “Study: Per Se Drugged Driving Laws Have Little Or No Impact On Traffic Deaths”

    1. Jarrod Langley says:

      A responsible cannabis user does not support drugged driving.

      [Paul Armentano responds: Agreed, as per NORML’s Principles of Responsible Use:


      II. No Driving
      The responsible cannabis consumer does not operate a motor vehicle or other dangerous machinery while impaired by cannabis, nor (like other responsible citizens) while impaired by any other substance or condition, including some medicines and fatigue.

      Although cannabis is said by most experts to be safer than alcohol and many prescription drugs with motorists, responsible cannabis consumers never operate motor vehicles in an impaired condition. Public safety demands not only that impaired drivers be taken off the road, but that objective measures of impairment be developed and used, rather than chemical testing.]

    2. Fireweed says:

      I keep saying this and I wish someone would seriously look into it:

      for the past 30+ years we’ve been doing an in vivo experiment concerning marijuana use and traffic safety and the results are in. It would appear that permitting marijuana use actually REDUCES incidents of traffic fatalities. Why? B/c drivers under the influence of mj tend to drive slower (not to the point of creating obstruction) and tend to leave more space between themselves and the vehicle ahead of them. also mj may tend to make drivers less aggressive.

      If you compare year by year mj-related laws with same year traffic safety statistics, you’ll find not only that there is no impact of decriminalization of marijuana or permission of medical use on traffic safety, except to lower incidents of traffic fatalities. Check it out for yourself and get back to me….somebody?

    3. Voice of the Resistance says:

      Marijuana is safer…Any one want to try it on a moterbike? It’s not like driving a car you know. It takes skill and good judment to get a powerfull 750 cc. motorbike capable of a top speed that’s well over 100 miles an hour down the road without geting killed, just saying…

    4. bongwater says:

      ive never had a moving violation.been driving for almost 20 years. im stoned probably at least half the time,but i have a very high tolerance….

    5. somedood says:

      FU!! Just legalize it or eat shit!

    6. Street says:

      I rode motorcycles for years and on many occasions have rode under the influence of cannabis and as long as your not an idiot to begin with its perfectly safe. I always rode slower and more cautiously after smoking but i do think its a better idea to drive or ride completely sober.

    7. Jarrod Langley says:

      I don’t think anyone with any sense supports someone driving any vehicle under the influence of cannabis. Cannabis is too special to not be responsible users! Do not drive! Plan ahead, work hard, stand up for what is right!!! I look forward to making this world a better place with you all!

    8. Galileo Galilei says:

      Meanwhile, there’s bars with parking lots.

    9. Galileo Galilei says:

      One more imposition of ideology over science.

    10. Mike says:

      Please sign this White House petition asking the federal government why they have a patent on the medical benefits of marijuana.