Webinar: Legalization of Marijuana: Implications for Traffic Safety

Thursday, October 25, 2018
11:00 – 12:00 am CT

Even though fewer Americans use marijuana than drink alcohol, and while marijuana carries a lower crash risk, it’s important to understand the dangers of driving while under the influence of marijuana (or cannabis). Delta-9-tetrahydrocannabinol (THC) is the psychoactive ingredient in marijuana and responsible for the intoxicating effect. Anywhere from 22 to 35 million people in the United States regularly use marijuana and the number will likely grow as more states legalize medical and recreational use. Nine US states have legalized the commercial production, distribution and possession of marijuana for recreational purposes for adults aged 21 and older. The District of Columbia (DC) has legalized the recreational use of marijuana but not the commercial production and sale. A national roadside survey conducted in 2013-2014 of more than 9,000 drivers on week-end nights showed that 12.6 percent of all drivers had marijuana in either their saliva or blood. Marijuana affects a number of critical driving skills — including alertness, concentration, coordination and reaction time. It makes it harder to judge distances and to react to traffic signs and signals. Young people who use cannabis before age 14 are 4 times more likely to have a history of dependence, and 3 times more likely to report driving under the influence of marijuana, compared with adults who start using cannabis at age 21 or older. A study for the National Highway Traffic Safety Administration (NHTSA) showed that 7.6 percent of over 3,000 drivers involved in crashes had marijuana in their system at the time of their crash. A week later at the same time, same day of week, same location, it was found that 6.1 percent of over 6,000 drivers on the roads but not involved in a crash had marijuana in their systems. After adjusting for driver age, gender and race/ethnicity, the risk of a crash for drivers with marijuana in their systems was 1.05 — which was not statistically significant. By comparison the risk of a crash for a driver with a blood alcohol concentration (BAC) of .05 was 2.07, a statistically significant elevated risk. It appears that while marijuana does impair some driving skills (divided attention, lane tracking, cognitive functions), the risk of a crash with marijuana is lower than for alcohol and some other drugs. While the statistical risk of a driver being involved in a crash with marijuana in their system is not currently significant, marijuana is known to impair certain driving skills.

WHAT SHOULD BE DONE? How can we limit marijuana impaired driving where it is legal? (1) Control the price via a tax and therefore consumption. (2) Limit or ban marijuana advertising. (3) Limit marijuana outlet locations (far from schools) and outlet density (via zoning laws). (4) Control the percent of THC (the active ingredient in marijuana) in marijuana. (5) Enforce the minimum legal purchase age of 21. (6) Enforce drugged driving using roadside oral fluid (saliva) testing. (7) Develop a standardized field sobriety test (SFST) for marijuana.  An ongoing study sponsored by NHTSA is collecting alcohol and drug data on seriously injured and fatally injured drivers (N=2500) in trauma centers in Jacksonville, FL, Miami, FL and Charlotte, NC, and will compare the incidence with drivers on the same roads, same time of day, same day of week one week later (N=5000) to determine the risk of a serious or fatal injury crash for marijuana and other drugs.

TAKE HOME VALUE AND IMPACT: Webinar participants will learn that:

  1. Certain minimum purchase age laws have good potential to curtail underage marijuana use (e.g. use THC, lose driver’s license; zero tolerance THC for driving; social host liability; and others).
  2. An estimated 25-30% of drivers arrested for DWI-alcohol also have other drugs in their systems.
  3. States need to establish separate statutes for alcohol-DWI and drug-DWI and more severe sanctions for the combination of alcohol and other drugs-DWI.
  4. Close monitoring of the legal states (Colorado, Washington, Alaska, Oregon, California, Maine, Massachusetts, Nevada and Vermont) is warranted.

This webinar is available to AAAM Members (all member types) at no cost. There is a charge of $50 (USD) for non-members. Pre-registration is required.

James Fell – Principal Research Scientist, National Opinion Research Center

Gary Milavetz, B.S., Pharm.D, FCCP, FAPh – Professor of Pharmacy, University of Iowa College of Pharmacy

Anthony C. Stein, Ph.D. – President & Technical Director, Safety Research Associates, Inc.


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