Weed Warning: Legalizing Marijuana Tied to Rise in Crashes in 3 States by HLDI

June 23, 2017

Legalizing recreational marijuana use in Colorado, Oregon and Washington has resulted in collision claim frequencies that are about three percent higher overall than would have been expected without legalization, a new insurance report has found.

The Highway Loss Data Institute (HLDI) report says that more drivers admit to using marijuana, and the substance is showing up more frequently among people involved in crashes.

The HLDI report authors note that although there is evidence from simulator and on-road studies that marijuana can degrade some aspects of driving performance, researchers haven’t been able to definitively connect marijuana use with more frequent real-world crashes. Some studies have found that using the drug could more than double crash risk, while others, including a large-scale federal case-control study, have failed to find a link between marijuana use and crashes. Studies on the effects of legalizing marijuana for medical use also have been inconclusive.

Colorado and Washington were the first states to legalize recreational marijuana for adults age 21 and older with voter approval in November 2012. Retail sales began in January 2014 in Colorado and in July 2014 in Washington. Oregon voters approved legalized recreational marijuana in November 2014, and sales started in October 2015.

HLDI conducted a combined analysis using neighboring states as additional controls to examine the collision claims experience of Colorado, Oregon and Washington before and after law changes. Control states included Idaho, Montana, Nevada, Utah and Wyoming, plus Colorado, Oregon and Washington prior to legalization of recreational use. During the study period, Nevada and Montana permitted medical use of marijuana, Wyoming and Utah allowed only limited use for medical purposes, and Idaho didn’t permit any use. Oregon and Washington authorized medical marijuana use in 1998, and Colorado authorized it in 2000.

HLDI also looked at loss results for each state individually compared with loss results for adjacent states without legalized recreational marijuana use prior to November 2016.

“The combined-state analysis shows that the first three states to legalize recreational marijuana have experienced more crashes,” says Matt Moore, senior vice president of HLDI. “The individual state analyses suggest that the size of the effect varies by state.”

Colorado saw the biggest estimated increase in claim frequency compared with its control states. After retail marijuana sales began in Colorado, the increase in collision claim frequency was 14 percent higher than in nearby Nebraska, Utah and Wyoming. Washington’s estimated increase in claim frequency was 6 percent higher than in Montana and Idaho, and Oregon’s estimated increase in claim frequency was 4 percent higher than in Idaho, Montana and Nevada.

“The combined effect for the three states was smaller but still significant at 3 percent,” Moore says. “The combined analysis uses a bigger control group and is a good representation of the effect of marijuana legalization overall. The single-state analyses show how the effect differs by state.”

Each of the individual state analyses also showed that the estimated effect of legalizing recreational use of marijuana varies depending on the comparison state examined. For example, results for Colorado vary from a 3 percent increase in claim frequency when compared with Wyoming to a 21 percent increase when compared with Utah.

Data spanned collision claims filed between January 2012 and October 2016 for 1981 to 2017 model vehicles. Analysts controlled for differences in the rated driver population, insured vehicle fleet, the mix of urban versus rural exposure, unemployment, weather and seasonality.

Collision claims are the most frequent kind of claims insurers receive. Collision coverage insures against physical damage to a driver’s vehicle in a crash with an object or other vehicle, generally when the driver is at fault. Collision claim frequency is the number of collision claims divided by the number of insured vehicle years.

HLDI said it will continue to examine insurance claims in states that allow recreational use of marijuana. Meanwhile, IIHS has begun a large-scale case-control study in Oregon to assess how legalized marijuana use may be changing the risk of crashes with injuries. Preliminary results are expected in 2020.

In addition to Colorado, Oregon and Washington, five other states and Washington, D.C., have legalized marijuana for all uses, and 21 states have comprehensive medical marijuana programs as of June. An additional 17 states permit limited access for medical use. Marijuana is still an illegal controlled substance under federal law.

“Worry that legalized marijuana is increasing crash rates isn’t misplaced,” says David Zuby, executive vice president and chief research officer of the Insurance Institute for Highway Safety. “HLDI’s findings on the early experience of Colorado, Oregon and Washington should give other states eyeing legalization pause.”

The Highway Loss Data Institute (HLDI) conducts studies of insurance data on vehicle losses and by publishes insurance loss results by vehicle make and model. Its sister research organization, the Insurance Institute for Highway Safety (IIHS), is focused reducing the losses from motor vehicle crashes. Both organizations are wholly supported by auto insurers and insurance associations.

State Efforts

The Governors Highway Safety Association (GHSA) has urged states to equip themselves with the latest research and recommends that they increase drug testing, bolster laboratory resources, track alcohol (DUI) and drugged (DUID) related driving data separately in state records, use surveys to gauge public attitudes, and evaluate the effects of any law or program changes.

The group has issued a guide, Drug Impaired Driving: A Guide for States, for states. Chief among the report’s recommendations is increased training for law enforcement officers to help them identify and arrest drugged drivers.

“As states across the country continue to struggle with drug-impaired driving, it’s critical that we help them understand the current landscape and provide examples of best practices so they can craft the most effective countermeasures,” said Jonathan Adkins, executive director of GHSA.

GHSA said this year five states are getting grants totaling $100,000 to implement Advanced Roadside Impaired Driving Enforcement (ARIDE) training and Drug Recognition Expert (DRE) programs. The states are Illinois, Montana, Washington, West Virginia and Wisconsin.

Related Research

The HLDI authors cite other research into drugs and driving including a 2016 IIHS survey that found that drivers in Colorado, Oregon and Washington were more likely to view marijuana as a highway safety problem than drivers in states without legalized use (Drivers say alcohol is bigger threat than pot).

A 2016 Columbia University study looked at traffic fatalities in 19 states before and after they enacted legalized medical marijuana laws. On average there was an 11 percent reduction in fatality rates, although the results varied across states. Seven states saw a reduction, while two had an increase, and the other 10 didn’t change.

Researchers using the National Advanced Driving Simulator found that while drivers under the influence of marijuana had trouble maintaining constant lane position, they drove more slowly and with more headway than drivers not under the influence.

About 1 in 5 weekend night-time drivers tested positive for at least one legal or illegal drug in the 2013-14 National Roadside Survey of Alcohol and Drug Use by Drivers conducted by the National Highway Traffic Safety Administration (NHTSA) (More drivers use marijuana, but link to crashes is murky).

A 2016 AAA Foundation study in Washington since legalization estimated that the prevalence of drivers in fatal crashes with marijuana in their blood roughly doubled from 8.3 percent in 2013 to 17 percent in 2014.

The National Highway and Traffic Safety Administration (NHTSA) examined the crash risk associated with driver drug use and found that drivers who tested positive for marijuana were overrepresented in the crash-involved population (More drivers use marijuana, but link to crashes is murky). However, they found no link between marijuana use and driver crash risk. The study, published in 2016, included 2011-12 data on police-reported crashes in Virginia Beach, Virginia, where it is illegal to use marijuana.

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