As Colorado grapples with a burgeoning legalized marijuana industry, authorities are becoming drug recognition experts, learning new tools in their fight against something that remains illegal: driving while stoned.
"If it slows down your reaction time by even a second, one second on the road at 70 mph is the difference between life and death," said Colorado State Trooper Joshua Lewis.
Of the drivers who got a ticket from the Colorado State Patrol in February for driving under the influence of drugs, 74 percent had used pot, according to the patrol.
In January, Colorado became the first state to legalize marijuana sales to anyone older than 21. Now the state wants to train 300 officers to spot the telltale symptoms of marijuana impairment: body tremors, a wobbly balance and dilated pupils.
It is illegal to drive under the influence of marijuana in the state and anyone with 5 nanograms or more of THC per milliliter of blood while driving could be arrested for a DUI, which could result in a fine or prison time, according to the state of Colorado website.
Columbia University researchers studied thousands of fatal car crashes in six states over a decade. They found that the number of drivers who tested positive for marijuana had tripled - from 4.2 percent to 12.2 percent - between 1999 and 2010.
During 56 hours of training, officers are taught a 12-step process for recognizing the symptoms of drivers who may be impaired by a variety of drugs or alcohol.
The state has also launched a new $1 million ad campaign that starts Monday and includes TV ads that target drugged drivers.
ABC News' Clayton Sandell contributed to this report.