DENVER — The number of drivers involved in fatal crashes in Colorado who tested positive for marijuana has more than doubled since 2013, federal and state data show.
A Denver Post analysis of the data and coroner reports provides the most comprehensive look yet into whether roads in the state have become more dangerous since the drug's legalization.
Increasingly potent levels of marijuana were found in positive-testing drivers who died in crashes in Front Range counties, according to coroner data since 2013 compiled by The Denver Post. Nearly a dozen in 2016 had levels five times the amount allowed by law, and one was at 22 times the limit. Levels were not as elevated in earlier years.
Last year, all of the drivers who survived and tested positive for marijuana use had the drug at levels that indicated use within a few hours of being tested, according to the Colorado Department of Transportation, which compiles information for the National Highway Traffic Safety Administration's Fatality Analysis Reporting System.
The trends coincide with the legalization of recreational marijuana in Colorado that began with adult use in late 2012, followed by sales in 2014.
However, Colorado transportation and public safety officials say the rising number of pot-related traffic fatalities cannot be definitively linked to legalized marijuana.
Positive test results reflected in the NHTSA data do not indicate whether a driver was high at the time of the crash since traces of marijuana use from weeks earlier also can appear as a positive result.
But police, victims' families and safety advocates say the numbers of drivers testing positive for marijuana use are rising too quickly to ignore and highlight the potential dangers of mixing pot with driving.
"We went from zero to 100, and we've been chasing it ever since," Greenwood Village Police Chief John Jackson said of the state's implementation of legalized marijuana. "Nobody understands it and people are dying. That's a huge public safety problem."
The 2013-16 period saw a 40 percent increase in the number of all drivers involved in fatal crashes in Colorado, from 627 to 880, according to the NHTSA data. Those who tested positive for alcohol in fatal crashes from 2013 to 2015 — figures for 2016 were not available — grew 17 percent, from 129 to 151.
By contrast, the number of drivers who tested positive for marijuana use jumped 145 percent — from 47 in 2013 to 115 in 2016. During that time, the prevalence of testing drivers for marijuana use did not change appreciably, federal fatal-crash data show.
State law does not require coroners to test deceased drivers specifically for marijuana use in fatal wrecks.
Among The Post's other findings:
—Marijuana is figuring into more fatal crashes overall. In 2013, drivers tested positive for the drug in about 10 percent of all fatal crashes. By 2016, it was 20 percent.
—More drivers are testing positive for marijuana and nothing else. Of the drivers involved in fatal crashes in 2014 who tested positive for cannabinoids, more than 52 percent had no alcohol in their system. By 2016, it had grown to 69 percent.
—In 2016, of the 115 drivers in fatal wrecks who tested positive for marijuana use, 71 were found with the psychoactive ingredient in marijuana in their blood, indicating use within hours, according to state data. Of those, 63 percent were over the state's limit for driving.
"We are discouraged by the rising numbers. We had awareness campaigns four months after legalization and thought we were getting out ahead of it," said Sam Cole, spokesman for the traffic safety division of the Colorado Department of Transportation, where the FARS data for the state is collected.
Pointing to a number of different studies, the industry counters that the data is imprecise and does not definitively link fatal crashes to marijuana use.
Taylor West, former deputy director of the National Cannabis Industry Association, said unlike alcohol, marijuana can remain detectable in the blood stream for days or weeks.
"So all those numbers really tell us is that, since legal adult-use sales began, a larger number of people are consuming cannabis and then, at some point . (are) driving a car," West said.