South Africa's  Constitutional Court announced announced on 18 September 2018 that cannabis is now legal in South  Africa for private use and private cultivation by adults. However,  there are a number of concerns and  questions around  regulation and control that still need to be addressed  to ensure the safety of both users and non-users – particularly when it comes to road safety.

As  with alcohol consumption, use of recreational cannabis leads to intoxication.  However, unlike alcohol, testing for marijuana intoxication is a lot  more complex than  simply doing a breathalyzer test. Laws and limits exist  for driving under the influence of alcohol but, as Tetrahydrocannabinol  (THC) - the principal psychoactive constituent of marijuana – remains in  a user’s system for far longer than alcohol does, it makes it  tricky  to establish limits and laws around marijuana use.

"There are a number of concerns and questions around regulation and control that still need to be addressed to ensure the safety of both users and non-users – particularly when it comes to road safety."

Since marijuana use has been  fairly common despite the legality of such, it’s highly likely that  there have  been drivers under the influence of THC (Marijuana) whilst  operating a vehicle up until now, although there are no real statistics  to confirm this.

According to Section 65 of South Africa's National  Road Traffic Act, “No person may drive a vehicle or occupy the driver’s  seat of a motor vehicle of which the engine  is running on a public road  while under the influence of intoxicating liquor or drug having  narcotic effect.”  

Driving under the influence of cannabis

In  theory, any person caught with even traces of marijuana in their system  whilst driving can currently be arrested and/or prosecuted, but  because it can remain in a person’s bloodstream for hours to days  after use, a person who tests positive for marijuana isn’t necessarily  intoxicated. At present, no limit has been established to determine how  much THC needs to be present in the bloodstream  for a person to be  considered intoxicated.

The  chance of a driver being tested for drugs in a road block are minimal  due to a lack of testing equipment available to officers and the fact  that there  are grey areas that need to be clarified and legislated. As a result, drivers that indulge in substances such as marijuana are less  concerned with being caught in a road block than if they have consumed  alcohol.

Currently,  THC can be detected in blood tests, urine tests and saliva tests. Saliva testing would be the most likely to be used to test  for  roadside marijuana intoxication, but test limits  need to be set up in order to establish more than just the presence of  THC. The process is also a lengthy one, with results only typically  showing within three to five minutes.


Saliva  tests comprise a disposable cartridge containing a cotton swab or  collection pad, similar to a large earbud. The person being tested would  need to  hold the swab in their mouth for a minimum of twenty seconds  to gather sufficient saliva (the swab changes colour when enough saliva  has been accumulated). This can be longer for those under the influence  of marijuana, as a known side effect is dry mouth.

The  swab is then inserted into the cartridge and results appear within  three to five minutes. The entire process takes  approximately 7  minutes, which is longer than a breathalyzer test  but still very necessary to ensure the safety of road user from  intoxicated drivers.

Traffic  enforcers are likely to only test based on visual suspicion of  intoxication, as the time constraints of saliva testing make it onerous  to test all  drivers at, say, a roadblock. It would make sense for  drivers to be tested on a random basis or possibly only if they are  suspected of being under the influence, giving visual cues such as  erratic or inconsistent driving.

Regardless  of the actual procedure, it is critical for relevant  governing bodies to be proactive in formulating regulations, limits and  testing requirements well ahead of legalisation.

It  is likely that legalisation of marijuana will only increase the number  of active users driving a vehicle while under the influence. Until  regulations  are in place, however, it will be extremely difficult if  not impossible to prove actual intoxication and there will be little to  stop these drivers from taking to our roads.

It  is essential that regulations are drawn and parameters set before  legalisation, to avoid a spike in intoxication-related traffic incidents  and ensure  that our roads remain safe.

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