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How does roadside drug testing work and why don’t you see this as much as RBT?

“How does roadside drug testing work and what drugs does it test for? Also, why don’t you see as many roadside drug tests being given? I see lots of RBT units but I’ve never seen anyone be drug tested.”

Roadside drug testing (RDT) has been around in Australia for some time now, with Victoria being the first state to introduce it in 2005. NSW (where it is called mobile drug testing (MDT)) introduced similar legislation in 2006, with other states and territories following later.

Although slightly different in different states and territories, the basic process is as follows. A driver of a vehicle is pulled over by the police, either at a random breath test (RBT) unit, or for some other reason. Before undertaking a roadside drug test, drivers must complete an alcohol test first, i.e., the breathalyser. If they pass, the driver will then be asked to provide a saliva test by placing an absorbent swab (it looks a bit like a pregnancy test!) in their mouth and rolling it across their tongue until a sample is collected. It will be screened by the officer at the roadside, with the result taking about 3-5 minutes. If positive, a second sample will be required for further analysis. If a second positive result is obtained further testing will be required to verify the result.

The reason you may not have seen RDT as much as you have seen RBT is that this is rarely a ‘random’ test like the one for alcohol where drivers are randomly chosen to complete the test. That’s why it’s not called a ‘random roadside drug test’. The saliva test takes longer to carry out than the breathalyser and is also expensive, so police are going to select drivers who they believe are more likely to have taken drugs (i.e., 18-25 year-old young men are more likely to be tested than women in their 70s). Originally, RDTs were more likely to be conducted in areas that police believed drivers were more likely to have used drugs (e.g., outside dance festivals, highways popular with truckies on long-haul journeys, or roads around ‘Schoolies’ destinations), although that has changed to some extent and they are now more likely to be conducted anywhere and anytime.

The saliva test has been designed to detect THC (the active component of cannabis), methamphetamine (speed or ice), MDMA (ecstasy or Molly), as well as cocaine in NSW and Queensland. They do not detect prescription drugs or common over the counter medications, such as cold and flu tablets or sinus medication (e.g., Sudafed).

It’s extremely difficult to say exactly how long these drugs will stay in your system and be detected by the saliva test. Different drugs affect different people in different ways – so there are no guarantees. According to police, THC (cannabis) will be detected by the first saliva test for several hours after use, but drivers who have inactive THC residue in their bodies from use in previous days/weeks shouldn’t get a positive result. Ecstasy or methamphetamine, on the other hand, may be detected 24 hours after use. Extremely large doses, other drugs taken at the same time, and differences in metabolism may affect how long methamphetamine, cocaine or MDMA can be found in the body. This has implications for people who are out on the road after having a big night out. Theoretically you could get busted for driving under the influence even though you feel completely together 24 hours later! A young man in Tasmania was one of the first people charged under their legislation and that was at 3.00pm the afternoon after he had taken the drug!

Under no circumstances should anyone use drugs like cannabis, ecstasy, coacine or speed and then get behind the wheel of a car – it’s dangerous for them and for everyone else on the road. The reason people take drugs is to ‘change where they’re at’ – the one place you don’t want to do that is when you’re driving. Even though you may not see roadside drug testing as much as RBT, it’s there and young people are getting caught drug driving. Be aware and remember that drug use and driving do not go together!

Please note that the advice provided is for information purposes only. As such, it cannot substitute for the advice of a legal professional.

First published: October 2015
Reviewed and updated: October 2023

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