With more states legalizing marijuana, it’s time to take a hard look at driving while under the influence.
Some states have decriminalized the possession of small amounts of marijuana. Others have passed laws allowing for limited use of medical marijuana. Still other states have laws that are even broader, such as Colorado and Washington.
So how do these cannabis laws come into play when you’re driving under the influence? And, what effect does marijuana actually have on your driving skills?
Get to know the laws in your state and, more importantly, understand how marijuana affects your ability to drive.
1. Marijuana slows your reaction time and ability to make decisions
Marijuana affects the part of the brain that controls body movement, balance and coordination. THC is also known to impair judgment and memory.
Studies show that driving while under the influence of marijuana negatively impacts attentiveness, perception of time and speed. What’s more, your ability to draw from past driving experiences is compromised when you smoke weed.
On the other hand, research suggests that THC causes more impairment in occasional users than it does for people who smoke regularly. Experts believe this may be due to the tolerance that frequent users of cannabis often develop.
2. The higher you are, the more risks you take while driving
Studies show that drivers who smoke only a small amount of weed can feel the effects and often rate themselves as impaired — even when they’re not.
In fact, research suggests that people with only a small amount of THC in their blood tend to be safer and more cautious drivers. For example, in simulated driving tests, they drive slower than they normally would and are less likely to overtake another vehicle. They also tend to allow for more space between their vehicle and others.
But driving high can still be dangerous. Problems seem to arise when larger doses of THC are present in the blood. These drivers tend to weave in and out of lanes more, react slower to traffic lights and unexpected obstacles and are less aware of their speed.
Overall, studies have concluded that higher doses of marijuana tend to cause greater impairment when it comes to driving.
3. The effect of marijuana is strongest during the first hour
Research suggests that people who drive immediately after using marijuana may double their risk of getting into an accident. This is because the effects of THC on driving are strongest during the first hour.
On the other hand, studies show that people who smoke a single joint of marijuana may be okay to drive 2-3 hours later.
But it’s important to note that THC remains in the blood even after its effects have worn off. In addition, people will often metabolize THC at different rates, which means some may feel the effects for up to five hours later. In fact, people who only smoke weed occasionally can have traces of THC in their blood for up to seven days.
Typically, law enforcement officers collect blood 90 minutes after an arrest and 3-4 hours after an accident.
4. Drivers can be tested for THC after being pulled over
Just like drunk driving, driving under the influence of drugs is a crime — even if your impairment happened due to prescribed drugs such as medical marijuana.
In the United States, law enforcement officers are trained to recognize signs of driving under the influence of marijuana through bloodshot eyes and increased nervousness. To measure levels of THC, states conduct chemical screening tests by collecting blood, urine, and/or saliva.
In Canada, the police use a standard sobriety test for marijuana that includes looking at a driver’s eyes and asking the person to walk, turn and stand on one leg.
Recently, police have been testing saliva-based roadside devices on suspected drug-impaired drivers. Two other devices, developed in Canada, test THC levels on a driver’s breath, similar to a breathalyzer. But neither device has been adopted by law enforcement yet.
Some states such as Colorado and Washington have established a legal limit for THC of 5 ng/ml. Other states are waiting for research that better defines THC and driving impairment before establishing a testing protocol.
5. Combining alcohol and marijuana is even more dangerous
Only 29 percent of Americans think that driving while high on marijuana is dangerous, according to a recent Gallup poll. Yet, when it comes to alcohol, 79 percent of Americans think that driving while intoxicated is a very serious problem.
Still, marijuana is the second most common drug used with alcohol. So it’s important to be aware of how dangerous this combination can be when driving.
Alcohol is a depressant. It works by slowing down the central nervous system, which means that normal brain functions are delayed. It also impairs hand-eye coordination and how you process information. Now, combine those effects with the effects of THC and you get a recipe for disaster.
Indeed, studies show that drivers who take alcohol and marijuana together experience greater impairment than drivers who use either substance on its own.