Will traffic deaths rise as states legalize pot?

WASHINGTON — As states liberalize their marijuana laws, public officials and safety advocates worry that more drivers high on pot will lead to a big increase in traffic deaths. Researchers, though, are divided on the question.

Studies of marijuana’s effects show that the drug can slow decision-making, decrease peripheral vision and impede multitasking, all of which are critical driving skills. But unlike with alcohol, drivers high on pot tend to be aware that they are impaired and try to compensate by driving slowly, avoiding risky actions such as passing other cars, and allowing extra room between vehicles.

On the other hand, combining marijuana with alcohol appears to eliminate the pot smoker’s exaggerated caution and seems to increase driving impairment beyond the effects of either substance alone.

“We see the legalization of marijuana in Colorado and Washington as a wake-up call for all of us in highway safety,” said Jonathan Adkins, executive director of Governors Highway Safety Association, which represents state highway safety offices.

“We don’t know enough about the scope of marijuana-impaired driving to call it a big or small problem. But anytime a driver has their ability impaired, it is a problem.”

Colorado and Washington are the only states that allow retail sales of marijuana for recreational use. Efforts to legalize recreational marijuana are underway in Alaska, Massachusetts, New York, Oregon and the District of Columbia. Twenty-three states and the nation’s capital permit marijuana use for medical purposes.

It is illegal in all states to drive while impaired by marijuana.

Colorado, Washington and Montana have set an intoxication threshold of 5 parts per billion of THC, the psychoactive ingredient in pot, in the blood. A few other states have set intoxication thresholds, but most have not set a specific level. In Washington, there was a jump of nearly 25 percent in drivers testing positive for marijuana in 2013 — the first full year after legalization — but no corresponding increase in car accidents or fatalities.

What worries highway safety experts are cases like that of New York teenager Joseph Beer, who in October 2012 smoked marijuana, climbed into a Subaru Impreza with four friends and drove more than 100 mph before losing control. The car crashed into trees with such force that the vehicle split in half, killing his friends.

Beer pleaded guilty to aggravated vehicular homicide and was sentenced last week to 5 years to 15 years in prison.

A prosecutor blamed the crash on “speed and weed,” but a Yale University Medical School expert on drug abuse who testified at the trial said studies of marijuana and crash risk are “highly inconclusive.” Some studies show a two- or three-fold increase, while others show none, said Dr. Mehmet Sofuoglu. Some studies even showed less risk if someone was marijuana positive, he testified.

Teenage boys and young men are the most likely drivers to smoke pot and the most likely drivers to have an accident regardless of whether they’re high, he said.

“Being a teenager, a male teenager, and being involved in reckless behavior could explain both at the same time — not necessarily marijuana causing getting into accidents, but a general reckless behavior leading to both conditions at the same time,” he told jurors.

In 2012, just over 10 percent of high school seniors said they had smoked pot before driving at least once in the prior two weeks, according to Monitoring the Future, an annual University of Michigan survey of 50,000 middle and high school students. Nearly twice as many male students as female students said they had smoked marijuana before driving.

A roadside survey by the National Highway Traffic Safety Administration in 2007 found 8.6 percent of drivers tested positive for THC, but it’s not possible to say how many were high at the time because drivers were tested only for the presence of drugs, not the amount.

A marijuana high generally peaks within a half hour and dissipates within three hours, but THC can linger for days in the bodies of habitual smokers.

Inexperienced pot smokers are likely to be more impaired than habitual smokers, who develop a tolerance. Some studies show virtually no driving impairment in habitual smokers.

Two recent studies that used similar data to assess crash risk came to opposite conclusions.

Columbia University researchers compared drivers who tested positive for marijuana in the roadside survey with state drug and alcohol tests of drivers killed in crashes. They found that marijuana alone increased the likelihood of being involved in a fatal crash by 80 percent.

But because the study included states where not all drivers are tested for alcohol and drugs, a majority of drivers in fatal crashes were excluded, possibly skewing the results. Also, the use of urine tests rather than blood tests in some cases may overestimate marijuana use and impairment.

A Pacific Institute for Research and Evaluation study used the roadside survey and data from nine states that test more than 80 percent of drivers killed in crashes. When adjusted for alcohol and driver demographics, the study found that otherwise sober drivers who tested positive for marijuana were slightly less likely to have been involved in a crash than drivers who tested negative for all drugs.

“We were expecting a huge impact,” said Eduardo Romano, lead author of the study, “and when we looked at the data from crashes we’re not seeing that much.” But Romano said his study may slightly underestimate the risk and that marijuana may lead to accidents caused by distraction.

Many states do not test drivers involved in a fatal crash for drugs unless there is reason to suspect impairment. Even if impairment is suspected, if the driver tests positive for alcohol, there may be no further testing because alcohol alone may be enough to bring criminal charges. Testing procedures also vary from state to state.

“If states legalize marijuana, they must set clear limits for impairment behind the wheel and require mandatory drug testing following a crash,” said Deborah Hersman, former chairman of the National Transportation Safety Board. “Right now we have a patchwork system across the nation regarding mandatory drug testing following highway crashes.”

Talk to us

> Give us your news tips.

> Send us a letter to the editor.

> More Herald contact information.

More in Local News

A firefighter stands in silence before a panel bearing the names of L. John Regelbrugge and Kris Regelbrugge during the ten-year remembrance of the Oso landslide on Friday, March 22, 2024, at the Oso Landslide Memorial in Oso, Washington. (Ryan Berry / The Herald)
‘Flood of emotions’ as Oso Landslide Memorial opens on 10th anniversary

Friends, family and first responders held a moment of silence at 10:37 a.m. at the new 2-acre memorial off Highway 530.

Julie Petersen poses for a photo with images of her sister Christina Jefferds and Jefferds’ grand daughter Sanoah Violet Huestis next to a memorial for Sanoah at her home on March 20, 2024 in Arlington, Washington. Peterson wears her sister’s favorite color and one of her bangles. (Annie Barker / The Herald)
‘It just all came down’: An oral history of the Oso mudslide

Ten years later, The Daily Herald spoke with dozens of people — first responders, family, survivors — touched by the deadliest slide in U.S. history.

Victims of the Oso mudslide on March 22, 2014. (Courtesy photos)
Remembering the 43 lives lost in the Oso mudslide

The slide wiped out a neighborhood along Highway 530 in 2014. “Even though you feel like you’re alone in your grief, you’re really not.”

Director Lucia Schmit, right, and Deputy Director Dara Salmon inside the Snohomish County Department of Emergency Management on Friday, March 8, 2024, in Everett, Washington. (Ryan Berry / The Herald)
How Oso slide changed local emergency response ‘on virtually every level’

“In a decade, we have just really, really advanced,” through hard-earned lessons applied to the pandemic, floods and opioids.

Ron and Gail Thompson at their home on Monday, March 4, 2024 in Oso, Washington. (Olivia Vanni / The Herald)
In shadow of scarred Oso hillside, mudslide’s wounds still feel fresh

Locals reflected on living with grief and finding meaning in the wake of a catastrophe “nothing like you can ever imagine” in 2014.

Lynnwood
Crash in Lynnwood blocks Highway 99 south

The crash, on Highway 99 at 176th Street SW, fully blocked southbound lanes. Traffic was diverted to 168th Street SW.

The view of Mountain Loop Mine out the window of a second floor classroom at Fairmount Elementary on Wednesday, Jan. 10, 2024 in Everett, Washington. (Olivia Vanni / The Herald)
County: Everett mining yard violated order to halt work next to school

At least 10 reports accused OMA Construction of violating a stop-work order next to Fairmount Elementary. A judge will hear the case.

Imagine Children's Museum's incoming CEO, Elizabeth "Elee" Wood. (Photo provided by Imagine Children's Museum)
Imagine Children’s Museum in Everett will welcome new CEO in June

Nancy Johnson, who has led Imagine Children’s Museum in Everett for 25 years, will retire in June.

Kelli Littlejohn, who was 11 when her older sister Melissa Lee was murdered, speaks to a group of investigators and deputies to thank them for bringing closure to her family after over 30 years on Thursday, March 28, 2024, at Snohomish County Superior Court in Everett, Washington. (Ryan Berry / The Herald)
‘She can rest in peace’: Jury convicts Bothell man in 1993 killing

Even after police arrested Alan Dean in 2020, it was unclear if he would stand trial. He was convicted Thursday in the murder of Melissa Lee, 15.

Ariel Garcia, 4, was last seen Wednesday morning in an apartment in the 4800 block of Vesper Dr. (Photo provided by Everett Police)
Search underway to find missing Everett child, 4

Ariel Garcia was last seen Wednesday morning at an apartment in the 4800 block of Vesper Drive.

The rezoned property, seen here from the Hillside Vista luxury development, is surrounded on two sides by modern neighborhoods Monday, March 25, 2024, in Lake Stevens, Washington. (Ryan Berry / The Herald)
Despite petition, Lake Stevens OKs rezone for new 96-home development

The change faced resistance from some residents, who worried about the effects of more density in the neighborhood.

Rep. Suzan DelBene, left, introduces Xichitl Torres Small, center, Undersecretary for Rural Development with the U.S. Department of Agriculture during a talk at Thomas Family Farms on Monday, April 3, 2023, in Snohomish, Washington. (Olivia Vanni / The Herald)
Under new federal program, Washingtonians can file taxes for free

At a press conference Wednesday, U.S. Rep. Suzan DelBene called the Direct File program safe, easy and secure.

Support local journalism

If you value local news, make a gift now to support the trusted journalism you get in The Daily Herald. Donations processed in this system are not tax deductible.