People driving while high on marijuana may be a bit safer than drivers who have consumed alcohol and less likely to have or cause a crash, reveals a new federal study.

Overall, statistics, when adjusted for factors such as age, race and gender, suggest there's little difference between driving stoned or sober when it comes to the risk of having a wreck, the National Highway Traffic Safety Administration (NHTSA) claims.

However, the NHTSA is quick to point out, the findings "do not indicate that drug use by drivers is risk-free," and acknowledges there are limitations to the study.

Those limitations "need to be carefully considered before more definitive conclusions about drug use and crash risk can be reached," the agency states.

While there isn't any statistically significant increase in the risk of a crash associated with marijuana use prior to driving, alcohol use resulting in a blood alcohol level of 0.05 or above will increase the risk of a crash seven-fold, according to the study.

Researchers are quick to point out the measurable presence in a person's system of THC, marijuana's primary active ingredient, is not as easy to correlate with impairment as blood alcohol levels.

"Most psychoactive drugs are chemically complex molecules, whose absorption, action and elimination from the body are difficult to predict," the report authors write in a Drug and Alcohol Crash Risk report (PDF), "and considerable differences exist between individuals with regard to the rates with which these processes occur. Alcohol, in comparison, is more predictable."

While several states have enacted laws that attempt to equate "marijuana-impaired driving" to drunk driving, the problem is THC can remain detectable in the body for days and possibly weeks, long past the point where they have any psychoactive effect on a person who may be pulled over while driving.

For the study, NHTSA researchers responded to vehicle accidents seven days a week, 24 hours a day, for 20 months in 2013 and 2014, recording information on drivers who tested positive for THC.

Experts said the study adds important information to the ongoing debate of driving under the influence of any substance, whether it's alcohol or marijuana.

"Nobody should drive while impaired by any substance, and that's why there are laws on the books to address it," says Mason Tvert, communications director for Marijuana Policy Project, a drug policy reform group. "While the research is pretty clear that marijuana use is not remotely as problematic as alcohol, it can cause impairment for some people when used at certain levels."

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