Traffic Fatalities Since Cannabis Legalization [Updated for 2020]

Medicinal marijuana is accessible to over 200 million Americans in 33 states and is legal recreationally in 11 states plus Washington D.C. While this is great news for weed advocates, there is a growing concern that people are driving under the influence of cannabis; a dangerous act that increases the risk of a traffic accident.

Marijuana is an intoxicant which can slow down a person’s reflexes and make them less aware of other motorists. However, it is difficult to measure the level of THC in a person’s blood. In Colorado, for example, motorists can be arrested if they have 5 nanograms of THC in their blood.

Alas, there is little scientific research to determine how that figure, or any other figure for that matter, correlates with impairment. It is entirely plausible that a person could have at least 5 nanograms in their blood even if they haven’t used weed for several days. Regular users could easily build up a tolerance so they wouldn’t be impaired with 5 nanograms of THC in their blood.

Law enforcement can pull over a driver and measure their blood alcohol content (BAC) with the aid of a breathalyzer. Although the marijuana equivalent is being developed by various companies, at present, police officers in many states have no method of checking an individual’s THC level.

Has There Been a Rise in Traffic Fatalities Since Marijuana Has Been Legalized in Specific States?

In March 2017, a truck crashed into a church bus in Concan, Texas. 12 people were killed. According to the National Transportation Safety Board (NTSB), the likely cause of the accident was the truck driver who was under the influence of a sedative and cannabis. The NTSB is adamant that we are seeing a major increase in drug-impaired drivers on American roads and something must be done as soon as possible.

In what is bad news for weed lovers, a study by Lane and Hall, published in Addiction in February 2019, found a correlation between marijuana legalization and an increase in traffic fatalities. The researchers looked at traffic fatalities in Colorado, Oregon, and Washington – three states that legalized recreational marijuana – along with nine neighboring jurisdictions.

In the first six months after legalization, Oregon, Colorado, and Washington had one additional traffic death for every one million residents. There was also a similar increase in traffic deaths in the neighboring jurisdictions, mainly because people drive across state lines to buy the weed. There was a total of 170 extra deaths during the six months.

However, this wasn’t the end of the story. The increase was only a temporary one, and the rate of traffic fatalities returned to normal after 12 months. The study did not investigate or explain the reason why this happened. One theory is that after the initial legalization of recreational weed, there was a rapid increase in inexperienced users who got behind the wheel without realizing how stoned they were.

What is becoming clear is that trying to determine whether weed causes an increase in road deaths is a difficult task. As the substance is federally illegal, there is relatively little research into its effects. We are seeing studies providing very different results when trying to answer the question.

In October 2018, a study by the Highway Loss Data Institute (HLDI) and Insurance Institute for Highway Safety (IIHS) discovered that there are 6% more traffic accidents in states where weed is legalized, compared to neighboring locations where marijuana is still illegal. The study compared statistical data from Oregon, Washington, Nevada, and Colorado (recreational weed is legal in all of these states) with Wyoming, Utah, Idaho, and Montana (where it is not recreationally legal).

The study even controlled for specific factors including driver age, location, weather, seasonality, and employment status. Paul Armentano, the deputy director of NORML, was skeptical of the findings. He outlined a few demographic differences that were not accounted for, including the number of vehicles on the road, tourism, and population density.

Other Research Shows Marijuana Has NOT Led to an Increase in Traffic Fatalities

For every study that suggests weed leads to an increase in road deaths, there is one which says it is not the case. A study by Aydelotte et al., published in the American Journal of Public Health in April 2017, looked at data from motor vehicle crash fatalities in Colorado, Washington, and eight ‘control’ states.

The team analyzed data from 2009 to 2015 which enabled them to look at traffic fatality statistics from before and after marijuana was made recreationally legal in Colorado and Washington. The study found that the motor vehicle crash fatality figures were similar in the periods before and after legalization.

An interesting study by Hansen, Miller, and Weber, published in The National Bureau of Economic Research in March 2018, created something called ‘synthetic controls’ to analyze whether marijuana legalization has increased traffic deaths.

The team created a hypothetical version of Colorado to see what would have happened had cannabis not been legalized in the state. The team found that recreational legalization didn’t have a noticeable effect on traffic deaths.

Marijuana and Traffic Fatalities: Correlation Not Causation

marijuana traffic fatalities

While there is a correlation between marijuana legalization and the number of deaths on American roads in areas where weed is legal, it doesn’t necessarily mean the herb is responsible. The Hansen study found that the number of fatal accidents where the driver tested positive for THC increased by 10% from 2013 to 2016. Moreover, there was a 92% increase in Colorado and a 28% increase in Washington.

However, this is an extremely simplistic, and inaccurate, way of looking at things. There are plenty of instances where drivers have been found with another substance, aside from THC, in their system. In the case of the truck driver in Texas, he had also used a sedative which could have impaired his ability to drive.

A combination of marijuana and alcohol is particularly dangerous. A French study by Martin et al., published in PLOS in November 2017, looked at the link between marijuana, alcohol, and fatal traffic accidents. The team found that you were 65% more likely to cause a fatal traffic accident if under the influence of marijuana compared to if you were sober. The study also discovered that you were 1680% more likely to cause a deadly car accident if under the influence of alcohol compared to being sober.

A study by the American Association for Clinical Chemistry (AACC) found that combining alcohol with cannabis increases the levels of THC in your blood. While using weed increased the risk of a fatal accident by 70%, the risk was 740% greater when you use alcohol, and 840% greater when you combine alcohol with marijuana.

Final Thoughts on Marijuana and Traffic Fatalities

Although the research hasn’t reached a definite conclusion, logic suggests that being under the influence of marijuana DOES increase the risk of a traffic accident. Regardless of whether you are using powerful opioids, weed, or alcohol, you WILL be impaired, and that increases the risk of causing, or being involved in, a road accident.

One of the big issues is that drivers don’t seem to have an understanding of the level of impairment they feel when under the influence of cannabis. As we mentioned earlier, while it is easy to evaluate the level of impairment when it comes to alcohol, there is no standardized marijuana test.

As marijuana legalization spreads to different states, there is an increased risk of motorists making bad decisions about using the herb before getting behind the wheel. It goes without saying that an increase in the number of weed users equates to an increase in the number of drivers who use the substance and are impaired while on the road. Motorists need to make better decisions, and law enforcement requires additional tools and training to detect impaired motorists before they cause an accident.