October 23, 2019

Roadside drug testing

roadside drug testing

Driving a motor vehicle safely is a complex task. You must be mentally alert, have clear vision and good physical coordination. This allows us to pay close attention to many things at once, and to react quickly when something unexpected happens. Taking drugs or other substances that affect the brain can reduce the ability to drive safely.

It is illegal to drive if you are under the influence of alcohol or other drugs. If you have consumed alcohol or drugs it is difficult to assess how much your own driving skills have been affected. It is also important to know that alcohol and other drugs can remain in your system for a period of time after consumption. If you consume alcohol or drugs in the evening you may not be safe to drive in the morning even if you no longer feel impaired, and a roadside drug test could return positive.

If you intend to drive, the safest option is to have no alcohol or other drugs in your system. This includes any prescription medicines that impact driving ability, your GP or pharmacist will be able to tell you if medication can impair your ability to operate a vehicle. It’s also important to remember that fatigue, and the after-effects of drug use (i.e. a ‘hangover’ or ’coming down’), can affect your driving skills.

This page explains drug testing of Victorian drivers and the steps you can take to stay safe. Each state/territory can vary with how they conduct roadside drug tests, if you would like to know more about roadside drug testing in your state/territory contact your relevant road authority.

What is drug testing?

Drug testing looks for traces of drugs in the body using samples of urine, breath, hair, saliva, or sweat. Testing may be used to detect illegal drug use, as well as the use of drugs not permitted while driving, or in specific workplaces or sports.

Passing a drug test may mean that either the drug is no longer in your body, or that the test can’t detect the traces that remain.

Types of drug tests used

Assessment of drug impairment test

In Victoria, police can choose to carry out an assessment of drug impairment to test drivers they believe may be under the influence of drugs.1 The assessment involves observing physical factors including balance, coordination, and behaviour.2 This test is used to indicate if a person is impaired, after the assessment police can require a blood or urine drug test in order to demonstrate a person has drugs present in their system.1

Saliva tests

Random roadside drug testing uses saliva samples to detect illicit drugs.3

Specially-trained police officers take a sample of your saliva, using an absorbent collector placed in the mouth or on the tongue.3 This test takes around 3 minutes. If the test is positive, it must be confirmed by laboratory testing before charges can be laid.3

In Victoria there are different drug driving offences a person can be charged with, and the penalties may vary. To find out more about Drug Driving offences and penalties visit Victoria Legal Aid or VicRoads.

Roadside saliva tests detect drugs that contain:

  • THC (Delta-9 tetrahydrocannabinol), the active component in cannabis
  • Methamphetamine, which is found in drugs such as ’speed’, ’base’, ‘ice’, and ‘crystal meth’
  • MDMA, a drug commonly known as ecstasy.3

It can be possible for some prescribed medications to show up on drug tests.4 If you would like to know more about medications and roadside drug tests contact VicRoads (if you are in another state or territory your relevant road authority), or ask your GP or pharmacist.

Breath tests

Alcohol breath testing is another common roadside test. Read more about blood alcohol content (BAC) testing.

How long can the drugs be detected?

Whether or not you have a positive test will depend on a number of factors including: the amount taken and the potency of the dose, other drugs you may have used at the same time, and your body's metabolism.

  • Cannabis: Random roadside saliva tests can detect THC (the active ingredient in cannabis) for around twelve hours after use for people who use cannabis infrequently or ‘recreationally’.5 However, for people who frequently use cannabis THC can be detectable for around 30 hours.5 It is important for people who use cannabis frequently to know that THC can be detected in urine samples for around a month after cannabis was last used – this is because the body stores THC in fat cells for a period of time.5, 6
  • Methamphetamine (‘speed’, ‘ice’): may be detected in saliva for around two days after use.7 When withdrawing or coming down from methamphetamine, people can experience fatigue, anxiety and irritability.
  • MDMA (‘ecstasy’): may be detected in saliva tests for around two days after use.8
  • Medications: If you’re taking medication it’s best to talk to your doctor about the combined impact on your ability to drive.

Each drug is different and can take different times to leave your body, during this time you may continue to be affected. Combinations of drugs can take even longer.

The safest option is to not drive after you have consumed alcohol or other drugs. Even if you feel okay to drive, you can still be affected and endanger both yourself and others on the roads.

State and Territory Road Authorities:

Australian Capital Territory

New South Wales

Northern Territory


South Australia



  1. Road Safety Act 1986. Sect. 55A (2013).
  2. Vic roads.Drug-driving penalties: Victoria State Government; 2019
  3. Towards Zero. Drug Driving: Victoria State Government; 2019
  4. Victoria Legal Aid. Drug driving: Victoria Legal Aid; 2018
  5. Mather L. The issue of driving while a relevant drug, Δ9- tetrahydrocannabinol, was present in saliva: Evidence about the evidence. Griffith Journal of Law & Human Dignity. 2016;4(2):21-52.
  6. Lee D, Huestis MA. Current knowledge on cannabinoids in oral fluid. Drug testing and analysis. 2014;6(1-2):88-111.
  7. Vic roads. Drug Testing: Victoria State Government; 2018
  8. Barnes AJ, Scheidweiler KB, Kolbrich-Spargo EA, Gorelick DA, Goodwin RS, Huestis MA. MDMA and metabolite disposition in expectorated oral fluid after controlled oral MDMA administration. Therapeutic drug monitoring. 2011;33(5):602-8.

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