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Driving High: Are Pot Smokers Causing More Accidents?

Effect of Driving High
Smoking Weed & Driving

As more and more states legalize recreational marijuana, debate rages on about driving high and it effects.  Can people drive just as well after smoking pot? Are those who drive high causing accidents?  How do police prove a driver was driving high?

One insurance research group found that collision claims went up 2.7 percent in the years after legalization of recreational marijuana in Colorado, Washington and Oregon.  The Highway Loss Data Institute compared those states with surrounding states.

The National Highway Traffic Safety Administration believes more study is needed before arriving at any conclusions.  At this time though NHTSA finds drivers high on weed show slower reaction times, difficulty estimating time and distance and drowsiness behind the wheel.

If reaction times are slower after smoking weed, then if and when conditions suddenly change, as happens on the highway, then accidents would seem more likely.

Driving High Cause & Effect

So called experts tend to agree that marijuana, unlike alcohol, does not act as a general central nervous system depressant, impairing multiple functions.  But as one Massachusetts court noted in considering the issue:

… the primary psychoactive substance in marijuana, tetrahydrocannibol (THC), is known to have an impact on several functions of the brain that are relevant to driving ability, including the capacity to divide one’s attention and focus on several things at the same time, balance, and the speed of processing information.

Commonwealth of Massachusetts v. Gerhardt, Mass. Supreme Judicial Court, September, 2017

The court in that case pointed out that studies offer no clear answers but that enough research exists to conclude that smoking marijuana does impair the ability to drive.

How Much Pot is Too Much?

The above case presented the issue of whether standard Field Sobriety Tests used by police to determine if a suspected drunk driver is too impaired to drive can be used in the driving high context.  The court concluded that while not perfect, observations made by police while giving the tests may be described in court.  At the same time, Massachusetts police after that case will no longer be allowed to testify as to their opinion that the tests proved that the person was in fact under the influence of marijuana.

What that means is that police may describe such outward observations as blood shot eyes, drowsiness, lack of coordination and other signs.  Police may not offer their opinion that those signs mean the person was under the influence of marijuana.

Other Ways To Detect High Drivers

The states of Colorado and Washington passed laws setting a limit of 5 nanograms of THC per milliliter of blood as a legal limit for driving high.  Modeled after the national standard setting .08 as the legal limit for alcohol, the idea offered a standardized way to prosecute high drivers.  But that easy answer came under immediate attack.

THC, the active agent in weed may show up in urine, saliva and blood tests for weeks after ingestion.  The THC lingers long after the effects wear out because it is stored away in body fat.  As for heavy users of marijuana, THC remains stored in body fat and tissue for extended periods of time.  So no clear link exists between THC in the body and impairment.

Drug Recognition Experts

Because the science of connecting up levels of marijuana consumption to actual impairment presents challenges, Massachusetts and other states are trying something new.  Some police departments train special Drug Recognition Experts – DREs – to learn specialized techniques for identifying drivers too high to drive.  These officers apply a 12 step, one-hour process looking at various signs exhibited by the suspect:

  • Blood Pressure
  • Pulse
  • Eye examination
  • Balance tests

But if the goal was to provide a gold standard accepted by the courts, not all judges allow such DRE experts to testify.  Detractors say the specially trained officers are not Emergency Medical Technicians and in fact have no medical training.  One study at the Washington State University found false positives from DRE tests ranged from 38 to 68 per cent.

Nonetheless, Colorado funds DRE schools with tax revenue from marijuana sales.  Since legalization of recreational pot Colorado started five DRE training schools. At one point 262 DREs worked in 83 different law enforcement agencies in Colorado.

Taking a slightly different approach, Massachusetts and other states do more basic training targeting those who drive high.  Called advanced roadside impaired driving enforcement, the training attempts to develop heightened skills over normal field sobriety training.

Is Driving High Even Illegal?

Only because I’ve actually fielded this question, we need to look at laws as they exist at this time.   The Massachusetts and New Hampshire drunk driving laws typify regulations in most states.

The New Hampshire statute makes it illegal to drive with a blood alcohol concentration (BAC) of .08 percent or above.  The other part of that law specifically mentions impairment while driving under the influence of alcohol or controlled substances and the like, which would include marijuana and other drugs.  You will find the actual language under RSA 265-A:2.

The Massachusetts drunk driving law takes a slightly different approach, coming straight out and mentioning marijuana. That statue first mentions the .08 blood alcohol level and then refers to the illegality of operating under the influence of “marijuana, narcotic drugs, depressants or stimulant substances.” This is M.G.L. chapter 90, Section 24.

So, yes, these and laws throughout the nation in fact refer to driving high, whether or not enforcement includes the issues we’ve addressed above.

How Many Drivers are High?

It’s a good question whether or not there are more drivers high on marijuana after legalization, in those states where recreational weed is now legal.  After all during the period of prohibition in American History alcohol flowed in “speak-easies” and elsewhere.  Take a look at Washington State, where in the first full year after the state legalized pot, 2013, reports claimed almost 25 percent more drivers tested positive for marijuana than before legalization.

Other statistics offered no clear conclusions.  The National Safety Council researched the number of drivers involved in fatal crashes who tested positive for marijuana in 12 states from 1992 to 2009.  This was before and after passage of medical marijuana laws. Only three states, California, Washington and Hawaii reported increases. Some say those increases were associated with changes in testing methods.  Then again, researchers at University of Colorado Medical School report the number of drivers involved in fatal motor vehicle crashes in that state who tested positive for pot more than doubled between 1994 and 2011.

The National Highway Traffic Safety Administration hopes research will more clearly document how pot affects driving. NHTSA and Washington state officials have also joined forces in research efforts to assess change in marijuana use by drivers before and after legalized recreational marijuana.

Marijuana Smokers and Accidents

Distracted driving already tops the list of factors causing accidents in the U.S.  More on distracted driving here.  A valid question arises whether or not adding legalized pot to the list of distractions will add another major danger to the nation’s highways.

Researchers and lawmakers continue to grapple with social change reflected in evolving laws. Law enforcement continues its search for acceptable ways to prove impairment by pot.  More and more states will continue to consider legalization of medical and recreational marijuana.

Serious accidents happen every day on the highways.  Distracted driving, drunk driving and now driving high are all varieties of negligence which causes accidents.  After an accident there are signs to look for.  They include erratic driving, the driver’s appearance and demeanor, the odor of fresh or burnt marijuana and the driver’s behavior on exiting the vehicle.  As with any accident, be alert, make a note of observations, and do nothing to escalate the attitude of the other driver.


Photo Credit: French Inhale by Chuck Grimmett on flickr, under license with Creative Commons.

Resources & Sources:

Chart of Marijuana Laws State-By-State.

Massachusetts Vows Crackdown on Those Driving High, The Cannabist, August 9, 2017

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Attorney Myers is a member of the American Trial Lawyers Association, Massachusetts Academy of Trial Lawyers, and New Hampshire Trial Lawyers Association. The Law Offices of Andrew D. Myers offer a broad range of legal services in personal injury cases in Massachusetts (MA) and New Hampshire (NH) areas.

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