A recent report from the Governors Highway Safety Association, an advocacy group that promotes traffic safety, has revealed that while the number of vehicle accidents caused by drunk drivers is falling, accidents caused by drivers who are under the influence of marijuana and other illegal drugs are on the rise.

The report, which included information from surveys taken by the National Highway Traffic Safety Administration, revealed that the percentage of drivers who tested positive for illegal drugs rose from 12.4 percent in 2001 to 15.1 percent from the year 2013 to 2014. In addition, of all the people who had been fatally injured in automobile accidents in 2013, 38 percent were found to have detectable levels of both illegal and legal drugs in there system. According to the a recent statement, this percentage is nearly the same as those testing positive for alcohol.

Blood and saliva tests revealed that the most common drug present in drivers’ systems was marijuana, followed by amphetamines, CNN reported. Other drugs commonly found in drivers’ systems are hydrocodone, oxycodone, anti-anxiety and depression medications, and cocaine. Currently, at least 15 states have imposed a zero tolerance policy when it comes to driving on possibly impairing drugs, but according to Dr. Jim Hedlund, however, there is more that can be done.

"Every state should look at [creating] laws. ... It's useful for all states because marijuana is not just confined to states where it is legal," Hedlund told CNN. "Alcohol-impaired driving is still a big deal, but we have paid more attention to it than to drug-impaired driving and it's time to pay more attention to drug-impaired driving."

In addition to training law enforcement to spot the behavioral signs of drivers under the influence of controlled substances, researchers in Canada are also working on building a breathalyzer that would be able to detect THC, one of the major components in marijuana.

This report suggests that marijuana and other illegal drugs can double a driver’s risk of crashing, but the evidence backing up this claim is unclear and highly debatable. Although researchers are not clear of how much marijuana impairs our ability to drive, they do know it is far less impairing than alcohol. For example, a 2014 study revealed that while a drunk driver with a BAC of .08 is 400 percent more likely to crash their car than a sober driver, drivers high on marijuana are only 25 percent more likely to get into a car crash.

When the researchers took other factors such as age, gender, and race into account, the risk of getting into an accident while high dropped to only around five percent. Some research has suggested that marijuana has an addictive effect on driving skills and only impairs drivers' abilities when used in addition to alcohol.

Source: Drug Impaired Driving: A Guide For What States Can Do. Governors Highway Safety Association. 2015.