Image Courtesy CBS 60 Minutes

Colorado Governor John Hickenlooper advises states exercise caution in the months after the legalization of marijuana. Photo credit: CBS News

These states would join four others and the District of Columbia where pot is already legal for recreational use, along with a number of others where it can be used for medical purposes.

Proponents say the change is long overdue and would, among other things, unburden an overtaxed justice system while no longer turning casual users into potential criminals. But critics, as well as some automotive safety advocates, are raising caution flags, warning that legalization could translate into trouble on the nation’s highways.

“I urge caution,” said Colorado Governor John Hickenlooper, whose state was, along with Washington, the first in the country to vote for decriminalization.

“My recommendation has been to go slowly and probably wait a couple years and let’s make sure we get some good vertical studies to make sure that there isn’t a dramatic increase in teenage usage, that there isn’t a significant increase in abuse like while driving,” Gov. Hickenlooper said during an interview on the CBS newsmagazine 60 Minutes. “We don’t see it yet, but we don’t have enough data to make that decision.”

For more than a decade, U.S. highway deaths came down sharply. That trend reversed last year, total fatalities rising about 8%, according to the National Highway Traffic Safety Administration. Several factors have been blamed, including distracted driving – especially motorists using cellphones and texting – as well as an overall increase in miles traveled.

But there is also concern that a growing number of motorists are taking to the highways while high. NHTSA data show that 21% of the 31,166 fatal crashes recorded last year involved at least one driver testing positive for drugs. That was up from just 12% in 2005 – but it was also down from 22% in 2014.

Some officials believe that accidents have risen in states where marijuana is legal.

How many of those were using marijuana hasn’t been reported, but another federal study found 15.1% of 11,000 drivers tested at night and during the weekend were using some form of illegal drug in 2013 and 2014, up from 12.4% in 2007. Marijuana use jumped from 8.6% to 12.6% during that period.

Proponents of marijuana legalization caution that such numbers can be misleading. While the effects of marijuana typically last a matter of hours, a casual user’s urine can test positive for THC, the psychoactive drug in weed, for up to 15 days. For moderate to heavy users, that can stretch to 30 and, in some cases, even 45 days – long after the drug has stopped having any impact on a motorist’s ability to drive.

(Police frequently resort to saliva tests that are likely only to remain positive for 12 hours, according to experts. On the other hand, a hair follicle test used by some employers may read positive for 90 days.)

Nonetheless, Glenn Davis, Colorado’s highway safety director, told USA Today that it is “very probable” that there has been an increase in the state’s roadway fatalities since the first marijuana shops opened up there in January 2014.

(Legal marijuana forcing states to examine impaired driving laws. Click Here for details.)

How much of an impact is far from certain – and is clearly less than the estimated 25% to 30% of today’s highway deaths blamed on the use of alcohol.

The activist group Mothers Against Drunk Driving, or MADD, has launched a campaign, according to its website, “to fight drugged driving.” The effort, however, is focused on a wide variety of drugs, both legal and illicit.

A number of states, such as Michigan, have led campaigns aimed at getting the message across that “buzzed driving” is a crime, just like drunk driving. It can be tougher to make a marijuana case stick, however, as it’s unclear when someone is found to have THC in their blood or saliva if that actually is impacting they’re driving.

But there have been arrests and, in June, Rodolfo Alberto Contreras became the first driver to be convicted of second-degree murder for being under the influence of weed at the time of the crash. He was accused of running a red light at about 80 mph, crossing a center divider and striking a Ford Explorer, killing David Aggio. Contreras, according to prosecutors, told authorities at the scene, “I want my weed.” He will now serve 20 years to life in prison, according to USA Today.

(Click Here for details about how legal marijuana is changing traffic laws.)

Authorities face several challenges. One is determining how much THC can impact a driver’s perceptions and motor skills. With as little as 13.1 ug per liter drivers “showed increased weaving that was similar to those considered legally under the influence of alcohol – normally considered a 0.08% blood-alcohol  ratio or above – according to the University of Iowa’s National Advanced Driving Simulator, in a study released in June.

The other challenge will be finding a reliable test that would show when a driver is actually under the influence. Barring drivers who might not have actually smoked for a week, perhaps even for several months, would be neither effective nor perhaps even pass legal muster.

Marijuana advocates contend that it is time to decriminalize the drug and stress that long-standing laws have done little to reduce its usage. They also argue that with legalization it becomes easier to regulate. Colorado now requires information, for example, on the dosage contained in edibles, an increasingly popular alternative to smoking weed.

Preliminary polls suggest voters are growing tired of the costly “war on drugs,” especially when it comes to marijuana, something that even President Barack Obama admits to have smoked in college. Many experts believe that if California legalizes the drug much of the country will soon follow.

(To see more about the rise in drowsy driving crashes, Click Here.)

That worries critics, and even skeptics like Colorado Gov. Hickenlooper. At the very least, they contend, the trend towards legalization will require state and federal officials to start tracking the data more closely to see if marijuana does redefine the concept of a high-way.

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