The most recent assessment by the National Highway Traffic Safety Administration, based on random roadside checks, found that 16.3 percent of all drivers nationwide at night were on various legal and illegal impairing drugs, half of them high on marijuana.
“Marijuana is a significant and important contributing factor in a growing number of fatal accidents,” said Gil Kerlikowske, director of National Drug Control Policy in the White House and former Seattle police chief. “There is no question, not only from the data but from what I have heard in my career as a law enforcement officer.”
As the medical marijuana movement has gained speed — one-third of the states now allow such sales — federal officials are pursuing research into the impairing effects of the drug.
“A lot of effort has gone into the study of drugged driving and marijuana, because that is the most prevalent drug, but we are not nearly to the point where we are with alcohol,” said Jeffrey P. Michael, the National Highway Traffic Safety Administration’s impaired-driving director. “We don’t know what level of marijuana impairs a driver.”
A $6 million study in Virginia Beach, Va., is attempting to remove any doubt that users of pot and other drugs are more likely than others to crash. Teams of federal researchers go to accident scenes and ask drivers to voluntarily provide samples of their blood. They later return to the same location, at the same time and on the same day of the week, asking two random motorists not involved in crashes for a blood sample.
The project aims to collect 7,500 blood samples and show whether drivers with specific blood levels of drugs are more likely to crash than those without the drugs, said John Lacey, a researcher at the nonprofit Pacific Institute for Research and Evaluation.
In other projects, test subjects are being given marijuana to smoke and then examined under high-powered scanners or put in advanced driving simulators to gauge how it affects their brains and their ability to drive.
Federal scientists envision a day when police could quickly swab saliva from drivers’ mouths and determine whether they have an illegal level of marijuana, but that will require years of research. Until then, police are in the same position they were with drunken driving in the 1950s, basing arrests on their judgment of each driver’s behavior and vital signs.
If police suspect a driver is stoned, they now administer a lengthy 12-point examination. The driver must walk a straight line and stand on one leg, estimate the passage of 30 seconds and have pupils, blood pressure and pulse checked.