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Driving safely requires full attention.

We need to be mentally alert, able to see clearly and have good coordination - this allows us to react quickly when the unexpected happens.

Alcohol, or drugs, affect the brain, reducing your ability to drive safely.

It’s illegal to drive with a blood alcohol level over 0.05, or under the influence of other drugs.

If you’ve been drinking or taking drugs, it’s difficult to know how much your driving skills have been impacted.

In fact, alcohol and other drugs can remain in your system for longer than you think.

If you have alcohol or drugs in the evening, it may not be safe to drive in the morning. Even if you no longer feel affected, a roadside test could return positive.1

Also, remember that fatigue, hangovers or come-downs from drugs can affect your driving skills.1

If you intend to drive, the safest option is to avoid alcohol or other drugs. This includes some prescription medications that can impact your driving. You can talk to your GP or pharmacist to learn more about the effects of prescribed medication.

Most of us are familiar with how roadside breath testing works – but you may be less familiar with roadside drug testing.

Here we explain, as an example, how Victorian driver drug testing works and talk you through the steps you can take to stay safe. (Note: each state/territory can vary in how they conduct roadside drug tests, but the implications are the same.)

If you want 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 drugs, as well as legal 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 any remaining traces.

Types of drug tests

Saliva tests

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

You can be tested by any Victorian Police officer – including motorcycle, highway patrol and unmarked vehicles.

The officer takes a sample of your saliva by placing an absorbent collector in the mouth or on the tongue for a few seconds. The sample is then analysed at the roadside, which takes around three minutes. If the test is positive, it must be confirmed by laboratory testing before charges can be laid.2

Roadside saliva tests can detect drugs that contain:

• THC (Delta-9 tetrahydrocannabinol): the psychoactive component in cannabis that gives people a ‘high’
• methamphetamine: found in drugs such as ’speed’, ’base’, ‘ice’ and ‘crystal meth’
• MDMA: also commonly known as ecstasy.2

What about drugs that aren’t detected by the roadside test?

If the police believe you’re impaired by a drug that can’t be detected in a roadside test, they may ask you to complete a standard impairment test. This involves assessing a person’s balance, coordination, and overall behaviour.2, 3

After the assessment, police can ask for a blood or urine test to determine if a person has drugs in their system.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.

If you want to know more about medications and roadside drug tests, contact VicRoads (or if you’re in another state or territory, contact your relevant road authority), or ask your GP or pharmacist.

How long can drugs be detected in the roadside test?

Whether or not you have a positive test will depend on a variety of factors including how much you’ve taken, 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 12 hours after use in people who use cannabis infrequently or ‘recreationally’.4 For people who frequently use cannabis, THC can usually be detected for around 30 hours.4 It’s important for people who use cannabis frequently to know that THC can be found 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.4, 5
• Methamphetamine: may be detected in saliva for around two days after use.6 When withdrawing or ‘coming down’ from methamphetamine, people can experience fatigue, anxiety and irritability.
• MDMA: may be detected in saliva tests for around two days after use.7
• 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 takes a different amount of time to leave your body. 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 be a danger to yourself and others on the roads.

State and territory road authorities:

Australian Capital Territory

New South Wales

Northern Territory

Queensland

South Australia

Tasmania

Victoria

Western Australia

Health worker in Tanzania performing an RDT. (Courtesy S. Patrick Kachur, CDC)

Unfortunately there is no simple answer for how long a positive drug test result will continue. 

The exact time frame required to return a negative test will depend upon a large variety of factors. These factors include the health of the person, the type of test conducted and the strength, amount and history of previous consumption of the drug.

This section should help you to understand detection periods and provide a general guide regarding the detection periods for various drugs.

Detection Periods - Summary

Ever heard that casual use of "Marijuana will show a positive result for 3 months in a urine test", or even "six weeks" or even "4 weeks"?

Normally explanations of horrendously long detection periods such as these are mixed with some scientific facts (such as THC being highly fat soluble). Yes, marijuana is highly fat soluble, however it also has quite a short "half life" so that casual use of the drug is likely to only present a positive result for 1 to 2 days in a urine test (however this could be 30 days from regular or chronic use).

The time frame can vary from person to person simply because all people have different conditions of general health, different fluid intake, metabolism etc. We also have no idea exactly how strong the drug was to start with and we have no idea about the total amount of the drug that might have been taken (illicit drugs don't tend to be provided with fabulous labels displaying volume and  % strength or be separated into individually packaged "doses").

We've provided a comprehensive explanation of the issues below including the following information:

• What is a detection period?
• So can we just use the detection period tables?
• Cut-off levels - what are they?
• Understanding cut-off levels and impairment
• Drug testing levels are different in each Country
• Drug testing cut-off levels can be different in each Organisation
• What are the major limitations?
• Detection Tables

However if you are in doubt and facing a drug test, or if you want to responsibly self-manage consumption so that you won't show a positive result in a drug test with the added benefit that you also have much less chance of exposing yourself and others to risk; you can also test yourself in the privacy of your own home.

What is a detection period?

A detection period is the simply the amount of time after consuming a drug that a particular testing method can still show a positive result.

For some methods (blood or saliva) this is usually measured in hours or days and in other cases in days or weeks (urine or hair).

So can we just use the detection period tables?

Detection periods can vary dramatically between people due to many factors (such as speed of metabolism, gender, drug interactions, genetic traits, age of the person or the type and strength of drug and the amount and way in which it is taken). So any reference to detection periods needs to be taken as a very rough guide only.

Detection period tables should not be relied upon to determine detoxification time or to determine when a person will provide a negative result to a drug test. This page contains some useful information which should be helpful for people wanting to understand this issue more thoroughly.

Cut-off levels - what are they?

Drug testing normally involves establishing the concentration of a drug above a certain level rather than just finding the presence of any level of the drug. Interestingly, not many people are aware of this!

A “cut-off” is the concentration at or above which a laboratory will deem to be a "positive" result. Cut-offs are usually set arbitrarily by an independent committee/ government body and reflect what most laboratories can reliably duplicate, generally reflect some recency of use and attempt to avoid extraneous influences such as passive inhalation or naturally occurring amines etc.

Drug testing Cut-off levels are different in each Country

In Australia and in the United States, expert committees have formulated and published recommended cut-off levels for a number of drug classes in what are referred to as "Standards".

These cut-off levels are not exactly the same between countries, for example the opiate cut-off level for urine testing in the United States is 2000ng/ml whereas the cut-off level in Australia for the same drug is 300ng/ml. This is a fairly dramatic difference (US is 666% higher than Australia).

Drug testing Cut-off levels can be different in each Organisation

Some organisations also adopt different cut-off levels for various drug classes. This means that anybody purchasing a home drug test kit should check the relevant cut-off level that might apply before selecting a test.

Naturally it can be a waste of time and money relying upon a test kit if it uses a different cut-off level to what is actually applied in a policy.

What are the major limitations?

People often fall into the trap of just looking at a detection period table and expecting that the time period stated in the table will apply to them.

The problem with this is that although detection period tables can be helpful in providing a general guide, they also have major limitations. The following table presents some of these limitations.

Having noted these limitations, some detection tables are provided below. As with all information provided on this site, this information is subject to our disclaimer policy which can be viewed in full by following the link at the bottom of this page.

These tables assume that the Australian Standard cut-off levels are used for the applicable substances listed.

Detection Tables (Urine & Saliva)

Stimulants

Hallucinogens and Other Compounds

Opioids and Morphine Derivatives

Depressants

Ok, if you've managed to make it all the way down here and still trying to work out if you might be positive or not - perhaps the best approach would be to test yourself.

Why not look over here and select a test kit to suit your needs and test yourself in the privacy of your own home