Marijuana effects on your driving

NIDA's Dr. Marilyn Huestis discusses new research, which used the most sophisticated driving simulator of its kind to mirror real-life situations. Results showed that marijuana use impairs one measure of driving performance.
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NIDA's Dr. Marilyn Huestis discusses new research, which used the most sophisticated driving simulator of its kind to mirror real-life situations. Results showed that marijuana use impairs one measure of driving performance.
By

California Weed

What stoned driving looks like and how California might regulate it

By Peter Hecht

phecht@sacbee.com

September 16, 2016 04:00 AM

The 2015 report from the Rocky Mountain High Intensity Drug Trafficking Area – a program run by the U.S. Office of National Drug Control Policy – offered a grim view of marijuana legalization and its impact on traffic safety in Colorado.

In 2014, the year that Colorado opened retail stores selling marijuana for adult recreational use, pot-related traffic fatalities spiked by 32 percent, the report said. Moreover, traffic deaths involving drivers testing positive for marijuana jumped to more than 19 percent of crashes, up from 10 percent in 2009, when stores just selling medical marijuana proliferated in the state.

On its face, the report could be politically significant in California. As state voters in November will decide on Proposition 64, an initiative to legalize possession and sales of marijuana for recreational use, the question of whether pot liberalization will make streets and highways more dangerous is a critical part of the debate.

Yet the politics and science surrounding the issue are murky at best. And the widely circulated report on impacts in Colorado serves to confirm why. That’s because, when it comes to analyzing marijuana and driving, even the data may be debatable.

Statistics from the Colorado Department of Transportation, analyzing the same 488 fatal traffic accidents in the state in 2014, produced a different number: Just over 12 percent of drivers – not 19 percent – tested positive for pot.

The difference was that state transportation officials only included drivers who met or exceeded Colorado’s impaired driving benchmark of 5 nanograms of THC – marijuana’s psychoactive ingredient – per milliliter of blood. The drug trafficking area report, an analysis prepared with major contributions from police agencies, included all drivers with any level of pot. Some of those drivers also had other drugs or alcohol in their systems.

“You see those numbers you think, ‘Oh my god, everybody’s high and getting into crashes,” said Glenn Davis, Colorado’s highway safety manager, whose office generated the more conservative analysis on marijuana-related accidents. “We really do not have accurate data. I recognize that marijuana impairment is going to be a challenge for us. I would say the increased availability of marijuana to the driving public has some impact on crashes, but we don’t know.”

Marijuana legalization advocates suggest impacts of pot use on driving danger may be even harder to quantify. They argue that the 5 nanograms measure – an investigative threshold in Colorado and a legal standard in Washington, another state where voters approved recreational marijuana use in 2012 – has little scientific reliability.

The problem, they say, is that THC detected in blood may apply to a stoned motorist who got in the car after smoking a joint as well as a sober driver who has pot metabolized in fat from using marijuana days or even weeks earlier.

“That doesn’t tell us anything about accident risks,” said Paul Armentano, deputy director for the National Organization for the Reform of Marijuana Laws, which advocates for marijuana decriminalization. He said there is no known pot impairment equivalent to the 0.08 percent blood-alcohol standard for drunken driving.

Proposition 64, which allows adults 21 years and older to possess, use and share up to an ounce of marijuana while imposing a 15 percent excise tax on retail sales, would maintain current state laws against driving under the influence of alcohol or drugs, including pot. It would impose no specific legal exposure standard for driving while stoned.

California by far already has America’s largest marijuana market. With a teeming state-sanctioned medical marijuana economy and a robust illicit one as well, one in seven California teens and adults used marijuana in the past year, according to 2012-14 survey data from U.S. Substance Abuse and Mental Health Services Administration. The California Highway Patrol doesn’t keep statistics on traffic accidents directly attributed to marijuana.

Proposition 64 opponents, including major law enforcement groups, argue that the initiative’s passage would present an implicit threat to roadway safety simply by expanding the legal availability and use of marijuana.

“The whole business model behind Prop 64 is that marijuana profits will increase with increased sales and use,” said Lauren Michaels, legislative affairs manager for the California Police Chiefs Association. “So we’re going to have more people over 21 using marijuana, which means more people under the influence of cannabis being on the roads.”

Her argument may be buttressed depending on how voters interpret marijuana crash statistics out of the state of Washington. A report by the American Automobile Foundation for Traffic Safety said 10 percent of Washington drivers involved in fatal crashes between 2010 and 2014 had marijuana in their system.

The report, which used any exposure level for marijuana, also noted that detections of marijuana in fatal crashes went up by 9.7 percent after stores selling recreational marijuana opened in the spring of 2014. However, the report said: “The results ... do not indicate that drivers with detectable THC ... were necessarily impaired ... or that they were at-fault for the crash.”

Researchers noted that their analysis of the Washington data also was complicated by the fact that 39 percent of the drivers who tested positive for marijuana also had consumed alcohol. Another 16.5 percent had other drugs in their system besides marijuana. And 10.5 percent had consumed pot, booze and other drugs.

Proposition 64 backer Nate Bradley, a former Wheatland police officer who heads the California Cannabis Industry Association, argues that the initiative will help officers sort out the mystery of stoned driving, even without a verifiable standard for impairment.

“The reality is most people who want to consume cannabis are around doing so now,” Bradley said. “Proposition 64 is going to fund a lot of training and take steps to stop future DUIs. It gives law enforcement the tools to go after impaired drivers that they don’t have now.”

The initiative would direct $15 million over five years to the Highway Patrol to determine “protocols and best practices” for detecting people driving under the influence of alcohol and drugs, including marijuana.

Proponents also say it would also trigger a major investment – 20 percent of marijuana tax revenue after mandated expenses – for additional law enforcement training and equipment. They say that money would also fund public education programs to curb marijuana-impaired driving.

California law enforcement agencies already have drug recognition training programs to teach officers how to recognize potential driving and behavioral indicators for people under the influence of marijuana or other drugs. Bradley said that can be extended to such things as recognizing specific effects of someone who has just smoked or vaporized marijuana or is feeling delayed effects of a pot brownie.

A 2015 study by researchers at University of Iowa’s Advanced Driving Simulator added to the debate over detecting marijuana-impaired driving vs. drunken driving. In the tests of 18 drivers – ages 21 to 37 – those who consumed pot wove in traffic lanes at more steady speeds while those using alcohol additionally veered out of lanes and often accelerated rapidly. “Cannabis-influenced drivers may attempt to drive more cautiously to compensate for impairing effects, whereas alcohol-influenced drivers often under-estimate their impairment and take more risks,” the researchers wrote.

The limited study raised issue with the 5 nanogram standard for marijuana, saying the equivalent of the 0.08 percent blood-alcohol impairment level for drunken driving could be a THC reading as high as 13.1 nanograms per milliliter of blood.

Additional stoned driving research is about to begin in California as result of legislation, signed by Gov. Jerry Brown, that allocated $1.8 million for a three-year study.

Dr. Igor Grant, a neuropsychiatrist who directs the Center for Medicinal Cannabis Research at the University of California, San Diego, said 60 subjects will be enrolled early this fall for the research, in which they operate driving simulators after consuming different levels of marijuana from a vaporizer. Grant said clinicians will examine ways in which pot reacts with the body and will also study alternatives for detecting marijuana exposure and potential impairment behind the wheel.

Dr. Mike Lynn, an emergency room physician at Alameda County’s Highland Hospital and a member of the clinical faculty at UC San Francisco, believes he has found a solution. Lynn is partnering with an Oakland startup, Hound Labs Inc., which is testing what it bills as the first dual alcohol and marijuana breathalyzer for use by officers.

Lynn said marijuana detected in the breath could determine if someone has smoked marijuana within the past hour or two, though not necessary establish actual impairment. But he said proof of recent exposure would be critical evidence for officers, who pull over motorists for erratic driving, to argue in court for drugged driving convictions.

“I think there is no shortage in the market for this,” said Lynn, who said the product could also be used by employers, particularly in transportation industries. “Whether I talk to parents or people in health care or law enforcement, many are surprised that we don’t have something already to get people off the street quickly if they are stoned.”

In Washington, authorities say the state’s 5 nanogram standard for marijuana-impaired drivers is having no impact on police decisions in marijuana-related driving stops. The blood tests, results introduced in court, come only after a driver is taken into custody.

Sgt. Clark Jones, a supervisor in the impaired driving section for the Washington State Patrol, said patrol officers are trained to look for different behaviors indicating motorists under the influence.

For drunken drivers, he said, the cue is often “driving that is really pronounced,” including dramatic weaving and speeding. With stoned drivers, it may be a lack of awareness of surrounding vehicles or of drifting in traffic. “Maybe they’re running red lights because they’re just not paying attention, because their inhibition is relaxed,” Jones said.

Expanded marijuana legalization in the state, he said, “increased the availability of marijuana to people who were not willing before to go out and buy illicit substances. It also really increased the awareness of law enforcement. We’re establishing a new baseline now. What is our new normal?”