DENVER, July 25 (UPI) -- Traffic stops are changing in states where marijuana -- either recreational or medical -- is legal.
Now, when someone is pulled over for impaired driving, officers in some states might follow a new protocol that could include blood or saliva tests, field sobriety tests and perhaps a request to participate in a pilot program.
In Maine, where recreational pot will go on sale Jan. 1, traffic safety experts are preparing for a slew of "novice users" who might get behind the wheel, said Scot Mattox, traffic safety resource prosecutor for the Maine Bureau of Highway Safety.
As pot is legalized in more places, it remains tough to prove in court that a driver who ingested marijuana was impaired, Mattox said.
"Your average jury will not be convinced of drug-impaired driving based on a nanogram level of THC in someone's blood," Mattox said. "Officers need to present other evidence, such as the way they're driving, the smell, the dilated pupils and the paraphernalia in the car."
Most impaired drivers smoking pot also had been drinking booze and often consuming other drugs, studies show.
In the past, when pot was illegal and an officer pulled over a driver for "probable cause" --swerving, speeding or other reckless driving -- the office could administer a breathalyzer test for alcohol and add charges of illegal possession of marijuana or paraphernalia.
There was no push to prove that marijuana was part of the impaired driving.
Now, in states where pot has recently become legal, like Massachusetts, Maine and Vermont, police departments are racing to train more officers in drug recognition and the signs of cannabis impairment, highway safety officials say.
The number of drug-impaired drivers is hard to estimate in part because some states lump drug-impaired traffic arrests with alcohol-impaired arrests. In Maine, toxicologists have not tested drivers in fatal accidents for drugs but only alcohol, Mattox said.
In Colorado, where recreational marijuana appeared on dispensary shelves in 2014, the state made early errors in reporting marijuana in arrests and toxicology results, which muddied the data about traffic safety and legalization, said Sam Cole, of the Colorado Department of Transportation.
"We tell other states, if you want to know the effect of legalization, get good baseline data on what things were like before legalization," Cole said.
Between 35 and 50 drivers a year involved in fatal crashes in Colorado test positive for the legal threshold of "active" delta-9 THC over the past two years -- less than 10 percent of total 640 fatalities in Colorado. Alcohol still remains the most common cause of the state's roughly 200 impaired-driving fatalities per year.
Research on the exact mechanism of marijuana impairment has been spotty because it is an illegal substance federally, said Melissa Kennedy of the American National Standards Institute board, a federal forensics research organization.
Studies do show getting behind the wheel after using marijuana can lower a driver's vigilance, slow reaction times, alter perceptions of time and distance, and affect the driver's balance and the ability to "track lanes."
But pot works on the body and brain differently than alcohol, which dampens the entire nervous system. Evidence of tetrahydrocannibol (THC) can stay in a person's body for a month. Some chronic users of marijuana may give a false-positive on a screening, or may even not be impaired -- even with high levels of marijuana in their bodies.
Technology companies are trying to develop a roadside measurement device, like a breathalyzer, that detects active "delta-9 THC" -- the compound that scientists believe causes impairment.
Mobile saliva swab tests have been approved in Canada, where recreational marijuana is legal nationwide. Breath vapor tests for THC still are in the research stage. Mobile blood tests have been used in Arizona.
But delta-9 THC melts away in the system between 30 and 90 minutes after it crosses the blood-brain barrier, although its effects can linger for up to six hours, researchers say.
In Colorado, state patrol officers ran a 2017 pilot program where people being arrested for possible marijuana-impaired driving were asked for a voluntary saliva sample. Only about 100 of those arrested agreed.
Along with changes in police procedures, traffic safety officials in newly weed-legalized states hope awareness campaigns convince people to not drive high.
"If you feel different, you drive different" is the slogan of Massachusetts' first campaign, printed on 1 million postcards inserted with orders in marijuana dispensaries. The cards remind dispensary customers that consuming weed in their car is illegal and they could face a $10,000 fine.
In Colorado, a "Drive high, get a DUI" campaign was the first public safety campaign. Vermont is launching the same campaign slogan this year.
It's not as if people weren't driving high before, but many didn't realize you could be charged for pot-impaired driving, Cole said. Others don't realize that medical marijuana can impair driving, or that tourists should not consume cannabis and drive.
"Everybody knows it's not OK to drive drunk. It's dangerous and there's a stigma against it," Cole said. "But many people think it's still OK to drive high."
Colorado traffic safety officials have shared their experiences with Alaska, California, Florida, Michigan, Nevada, Nebraska, New Jersey, Oklahoma, Texas, Wyoming, and West Virginia. They also have made presentations at the Governors Highway Safety Association and the National Conference of State Legislatures, Cole said.
Another lesson to learn: Colorado had a large culture of illicit cannabis users when recreational pot went legal via a state referendum.
"There's a pride among marijuana users," Cole said. "It's almost a religion when it comes to marijuana. One of the big takeaways we've learned is that marijuana users like fact-based informational campaigns. They don't like fear-based, or scare-based campaigns. You have to build their trust."
Images of auto wrecks and pot paraphernalia don't work, he said.
But partnering with marijuana business associations has worked well. Outreach campaigns have included mobile phone ride-share coupons and tourist reminders.
"You want to remain very neutral and not show judgement. It's legal in this state," Cole said.
The most important lesson from Colorado is to use tax money generated by marijuana for drug awareness, addiction treatment and traffic safety, he said.
"That's an upside of legalization. If you legalize and you tax, you must make sure those taxes go back to educate the public," he said.