If you are pulled to the side of the road on the notion of drunk driving, completing the difficult tasks of following a pen with your eyes, walking in a straight line, and standing on one leg for 30 seconds clearly proves you are not drunk. Eighty-eight percent of drivers under the influence of alcohol have been caught by these tests.

But catching stoned drivers is not that easy; health officials and law enforcement don’t yet have the data or the tools to address the concern as effectively as that of drunk driving.

In the first six months since recreational marijuana was legalized in the state of Washington, 745 drivers stopped by police tested positive for THC, the drug’s active ingredient, in their blood.

“The legalization of recreational marijuana does not affect me as of yet, but I am just as concerned with stoned drivers as I am drunk drivers,” said Heriberto Casanueva Jr from Loveland, Colorado, Co-Founder & Owner of Spidertrax Inc.

So how do cops try to find out if weed is your co-pilot? Well, police have come up with drug-detection tactics that help them spot stoned drivers. It’s all based on observation. Usually drunk drivers will speed and run stop signs, while stoned drivers are more cautious and will drive slower than the speed limit. Once they stop suspicious drivers, cops will check for bloodshot eyes, watery eyes, slow reaction, the odor of pot, and then push towards the blood test that will provide them with THC levels.

A person who refuses this blood test will have their license revoked on the spot for a year. In contrast, those who agree to the blood test can get it back within a few months. Blood test results can take anywhere from two to six weeks to come back in. In Colorado, the legal limit for THC in the blood system is 5 nanograms per milliliter of blood.

There is a bit of controversy with these new DUI laws because, unlike alcohol, marijuana stays in the blood long after the high wears off a few hours after use, and there is no quick test to determine someone’s level of impairment.

“THC is a molecule that really loves human fat, and when you ingest it, it sticks in the fat, and then it slowly seeps out over the course of a week, or a month if you are a heavy user,” said Timothy Fong, an addiction psychiatrist at the University of California, Los Angeles on South California’s Public Radio.

Measuring 5 nanograms does not necessarily mean testing someone’s level of impairment because marijuana affects users differently. Someone who smoked pot a week ago or two months ago could still show THC levels higher than 5 nanograms.

The act of smoking marijuana is gradually being accepted by many Americans. Marijuana is smoked by about 5.4 million Americans daily. President Obama has even admitted to smoking weed when he was a teen. Obama explained, “As has been well documented, I smoked pot as a kid, and I view it as a bad habit and a vice, not very different from the cigarettes that I smoked as a young person up through a big chunk of my adult life. I don’t think it is more dangerous than alcohol.” The fact that it’s becoming popular and widely used cannot be denied.

“I believe in small government and the liberty of people. I personally have no interest in this drug.  But I look at it in the same way as alcohol. When alcohol was prohibited in the 1930’s all it did was create a black market for the product which led to the birth of organized crime,” said Heriberto Casanueva. “I personally feel that people should be allowed to use this drug. I would like to see it used in a person’s home and not in public places. And there should be laws against driving while under the influence of the drug. With these measures in place, the use of this drug should little to no effect on others.”

A recent assessment by the National Highway Traffic Safety Administration, based on random roadside checks, found that 16.3% of all drivers nationwide at night were on various legal and illegal impairing drugs, half them high on marijuana.

“I skateboard a lot with my kids. We spend a great deal of time around younger people at skate parks. The drug has been present at all the parks we spend time at well before it was legalized. I personally think the drug is a bad thing. I think very little good comes out of the use of it. It may help certain people but for the most part I see it abused similar to alcohol,” said Heriberto Casanueva when asked if he has had any experience with people who use the drug.

“Smoking marijuana is a big deal if you use it and then get behind the wheel,” said Jonathan Adkins, executive director of the Governors Highway Safety Association on South California’s Public Radio. “We need to have the same cultural intolerance for marijuana use behind the wheel as we do with alcohol.”

In a 2012 study published in the journal Psychopharmacology, only 30 percent of people under the influence of marijuana failed the drug-detection tactics the cops use. Frequent pot users are more likely to pass the test than new or occasional users. In contrast to drinking, where both a young man on his first drunk spree and an experienced alcoholic will stumble out of a bar, someone who just smoked his first blunt will react differently from a person who smokes four times a day.

“It is difficult to generalize how people react to marijuana while driving. It all depends on the dose you take and how you react to it and as you might know, everyone reacts differently when smoking marijuana. I don’t see how someone would be able to drive better under the influence of ANY substance that can possibly impair your ability to drive. Whenever someone goes out there driving while drunk/high they are not only putting themselves in danger, they are putting others in danger as well,” said Allen Greene, a frequent smoker from Colorado, in response to a theory that driving stoned is better than driving sober.

However, research in Colorado has shown that there has been a decrease in drunk-driving and less fatal accidents on the streets. It’s been assumed that people have laid off the liquor in preference to weed. Driving under the influence of marijuana is dangerous, but it has proven to be less dangerous than driving under the influence of alcohol.

Stoned drivers are more knowledgeable of their intoxication, unlike drunk drivers, so they tend to drive below the speed limit and with much more caution. Driving with an excess amount of marijuana in your system has been associated with fatal accidents. Even though they are more cautious, when a situation requires quick reflexes, high drivers won’t be able react in time to take control.

This doesn’t mean that fatal car accidents are increasing; it just means that marijuana use is increasing and is becoming more acceptable in society. So, more people are getting high and more of them are driving. In 2010, 32 people involved in fatal crashes had ingested marijuana, according to the Colorado Department of Transportation.

Medical and recreational marijuana may be legal in some states, but driving while impaired by any drug is illegal in all states.