"Traffic fatalities linked to marijuana are up sharply in Colorado. Is legalization to blame?"

The title of this post is the headline of this big long article Denver Post article exploring marijuana reform's impact on roadway safety.  Here are excerpts:

The number of drivers involved in fatal crashes in Colorado who tested positive for marijuana has risen sharply each year since 2013, more than doubling in that time, 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.  Colorado transportation and public safety officials, however, 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 — which have grown at a quicker rate than the increase in pot usage in Colorado since 2013 — are rising too quickly to ignore and highlight the potential dangers of mixing pot with driving....

Estimates vary for how much marijuana use has increased in Colorado since legalization.  Surveys by the federal Substance Abuse and Mental Health Services Administration found that use within 30 days rose from about 12 percent of Colorado adults in 2013 to 17 percent in 2015, a 42 percent increase.  But the Colorado Department of Public Health and Environment published a survey last year putting adult use at 13 percent in 2015, indicating a slower rate of growth.

The number of drivers involved in fatal crashes testing positive for marijuana rose 88 percent from 2013 to 2015, FARS data show.  The numbers are not strictly comparable as the usage estimates would take into account Colorado’s population growth rate of roughly 1.8 percent a year....

Law enforcement officials, prosecutors and public policy makers concede there’s still too little information about marijuana and how it’s detected to understand just how much the drug is affecting traffic fatalities.  Even coroners who occasionally test for the drug bicker over whether to include pot on a driver’s death certificate.  “No one’s really sure of the broad impact because not all the drivers are tested, yet people are dying,” said Montrose County Coroner Dr. Thomas Canfield.  “It’s this false science that marijuana is harmless, … but it’s not, particularly when you know what it does to your time and depth perception, and the ability to understand and be attentive to what’s around you.”...

The trends in the state appear nearly identical in Washington state, where recreational marijuana was legalized at about the same time.  Officials there have been tracking the drug’s impact on driving much more carefully and for a longer period, statistics show. What Washingtonians have been seeing is starting to be revealed here: “Drug-impaired driving is now eclipsing alcohol, and that’s frustrating,” said Darrin Grondel, director of Washington’s Traffic Safety Commission, which is gathering and studying the data.

However, Colorado’s understanding is due to deepen.  The legislature last session passed House Bill 1315, which mandates a vigorous analysis of traffic fatalities statewide and the extent to which marijuana and other drugs are involved and prosecuted.  As part of that project, state police have re-analyzed about a third of blood samples taken from suspected drunk drivers in 2015 and, according to a person familiar with that project, found that more than three in five also tested positive for active THC.

Coroners and police say they have no idea just how many drivers – dead or alive – have active THC in their system because so few of them are tested for it in the first place.  Colorado’s Department of Public Safety in March 2016 said barely half of all drivers involved in fatal crashes were tested for drugs – and 81 percent of the ones tested were dead.  That has remained relatively unchanged since 2012, when 45 percent of all drivers in fatal crashes were tested.  That’s because Colorado’s DUI laws are such that a positive reading for alcohol impairment quickly results in a suspended license.  Not so for marijuana....

Transportation officials are concerned not only with pot-related fatalities but with the overall rise in traffic deaths.  While CDOT doesn’t see the number of drivers involved in fatal crashes as “a reliable measurement,” preferring metrics such as the number of actual crashes and fatalities, it does note that those are also on the rise. The reason, said CDOT’s Cole, is probably due in part to an increase in motorcycle fatalities, pedestrian deaths, cellphone use — and marijuana.