How long does marijuana stay in your system?

Road side drug tests carried out by the police are designed to detect drivers who are behind the wheel within 12 hours of consuming cannabis.

Marijuana in body system

How long after use could cannabis users be impaired?

Studies show that marijuana can distort a person’s sense of judgement, motor coordination and focus. Due to these effects, it could undermine driving skills. These studies also show that since the drug can alter the sense of time and distance, driving under its influence might lead to poor speed control, which could be disastrous for the driver and other road users. With floundering focus and impaired perception of speed and space, drivers under the influence of cannabis can pass road signs and fail to notice them clearly, miscalculate the speed and distances of oncoming vehicles, and react slowly when steering the vehicle in the right direction.

According to research, the slightest impairment of mental function during driving significantly elevates the risks of an auto crash.



When is it a good idea to drive under the influence of Cannabis?

One of points often raised in the debate about marijuana use is that the influence of the drug on the human body varies depending on the person’s unique body chemistry. There are many marijuana users who claim the drug actually enhances their focus, mental clarity, and composure, ultimately enhancing their driving skills. When considering the unique composition of each individual’s body chemistry, such claims may also be supported by research -- but most likely only within the first few minutes of driving. That’s because the intoxicated driver soon begins to drift away and to pay less attention to the vehicle in motion.


While some people may claim to have no problems driving under the influence of weed due to their unique body composition, the same cannot be said about majority of people. Source

The majority of studies on the connection between cannabis use and road accidents do not portray favorable prospects for weed users who regularly go behind the steering wheel shortly after using cannabis products. According to the United States national Highway Traffic Safety Administration (NHTSA), one in four drivers responsible for auto crashes are marijuana users under the influence.



How long does Cannabis in your system inhibit your ability to drive?

Road side drug tests carried out by the police are designed to detect drivers who are behind the wheel within 12 hours of consuming cannabis. However, that’s not to say that weed impairs everyone’s driving skills for 12 hours after consumption. A lot of factors influence the outcome of drug use on driving skills. These include the amount and potency of the drug consumed and the individual’s metabolism and unique body chemistry. Motor control, for instance, can be fully restored more quickly in some people in comparison to others after consumption.



Current Australian roadside tests for cannabis are inadequate

Legal experts have been campaigning for a speedy revision of contradictions in the current roadside drug test policies. These contradictions have resulted in positive road side saliva test results weeks after they person consumed marijuana products, or even after they only used hemp products like balms. Many judges, prosecutors, and legal practitioners assert that the majority of drug driving offenders probably were not significantly impaired at the time of their offense.

Experts warn that current road side policies and testing devices will congest the justice system with cases where people used the drug legally or waited days, weeks or even months after taking the drug before getting behind a steering wheel, but still show a false positive.Penalties for drug-driving offenses are quite hefty, and could mean having a license rescinded, being sent back to driving school, or ending up with a criminal record.



The new breathalysers for cannabis will be much more accurate

The science of THC’s interaction with the body many layers of complexities. As such, a reliable THC breathalyzer needs to be highly sophisticated. Although alcohol breathalyzers can provide direction to researchers developing the THC version, there is still a lot that needs to be taken into consideration, especially given the differences between the metabolism of alcohol and THC in the body. Promising THC breathalyzer developments are designed to measure the vapor pressure of THC, which can be detected in picograms -- a scale 1000 smaller than the nanogram, which is used to measure components in liquids. Tara Lovestead, a research chemical engineer for the National Institute of Standards Technology, points out that, “Not only is the vapor pressure of THC really low, it is predicted to be approximately 100 million times less than ethanol’s vapor pressure,” “A breathalyzer designed to detect THC will have to be extremely sensitive, able to capture a needle in a haystack” she added.


Breath analysis is the most effective way to measure THC within just a few hours after consumption. Source

The devices will be capable of detecting THC in the breath two hours after consumption in occasional users and 4 hours after consumption in regular users.



How can you be sure you'll never be stopped for driving under the influence by police?

Mobile cannabis tests occur randomly, and you can be pulled over and tested out of the blue. According the government’s drug driving policy site, “anyone who is operating or attempting to put a motor vehicle in motion may be required, by law, to undertake a random roadside saliva test for the recent consumption of THC (cannabis), Methylamphetamine (speed, ice or crystal meth) and MDMA (ecstasy)”.

These tests are designed to make life safer for people who do choose to use cannabis products, as well as any people around them who could be negatively impacted by any impairment. Developing a reliable test for THC levels is more complicated than the traditional alcohol breathalyzer, but it is necessary to both keep people safe and eliminate false positive results that could see people prosecuted unfairly. While the effects of marijuana are different from person to person, it is in everyone’s best interests to ensure that testing is accurate and fair.