Life in Australia Guide

In Australia, drug driving has a different legal structure from drink driving. There are broadly two offences. The first is a presence offence, which is made out simply if a specific illegal drug is detected in a saliva or blood test. It is a zero-tolerance approach that is unrelated to whether you were intoxicated or whether your driving was actually impaired. The second is an impairment offence, which is made out if you drive while affected to the point that your ability to drive is impaired, even by a legal medication such as a prescription or OTC medicine. Distinguishing between these two structures is the starting point for understanding drug driving rules. The specific drugs detected, penalties, and testing methods differ from state to state and are amended frequently, so always check the latest rules of the transport authority and police in your state.

MDT (mobile drug testing) is enforcement in which police take a driver's saliva at the roadside to check for the detection of illegal drugs. Like breath testing, it can be carried out on any driver without warning, and refusing the test without a valid reason can itself be a separate offence. The drugs tested for, the equipment, and the secondary confirmation process differ by state, so check the official guidance of your state police and transport authority for details.

If you are taking anything such as prescription medication, OTC medicine, or medicinal cannabis, check the following sequence before you get behind the wheel. Whether a particular medication is safe for driving varies by person, dose, and combination, so this guide cannot state it definitively; as a rule, confirm the final judgement through a consultation with a pharmacist or GP (your regular doctor). For the meaning of medication warning labels and pharmacist consultation itself, also refer to the pharmacy and PBS guide.

• First check the driving warning symbols and wording on the medication box or packet (e.g. may cause drowsiness, caution when driving or operating machinery).
• Check with a pharmacist or GP whether the medication you are taking contains an illegal drug substance (detectable, e.g. THC), and whether it could impair your driving.
• If you feel impaired — drowsiness, reduced concentration, dizziness, etc. — postpone driving and use public transport or alternative transport.

Even for the same medication, the offence structure that applies differs depending on whether the substance is illegal and whether it impairs your driving. We have set out four representative cases from the perspective of presence (detection) and impairment. The following is for understanding the structure; confirm the assessment of individual cases with a GP, pharmacist, or legal help. For reference, the legality (state-by-state differences and visa implications) of cannabis and the like is covered by the alcohol, tobacco and vaping guide, while drug-affected riding of e-scooters and e-bikes is covered by the e-scooter and e-bike guide.

These are items to check before driving when you are taking medication. Checking them in order can reduce both the presence and impairment risks together.

• Have you compiled a list of all the medications you are taking (including prescription, OTC, medicinal cannabis, and supplements)?
• Have you checked each medication's driving warning label and side effects (drowsiness, dizziness)?
• Have you checked with a pharmacist or GP whether it contains an illegal drug substance (detectable)?
• Have you checked for yourself whether your current physical state (drowsiness, concentration) is not impairing your driving?
• If you are the least bit unsure, have you arranged alternative transport?

These are the points that are especially misunderstood about drug driving. Avoid the following five.

• I have a prescription, so it's fine — the presence of an illegal substance (such as THC) can be an offence regardless of a prescription, and even a legal prescription medication is an offence if it causes impairment.
• I'm not intoxicated, so it's fine — a presence offence is based on whether it is detected rather than how intoxicated you are, so it can be made out even if you feel perfectly fine.
• A few days have passed, so it's all gone — how long a drug stays in your saliva differs by person and by drug, so self-judgement is dangerous.
• Ordinary cold medicine doesn't matter — even if it is not an illegal substance, it can cause impairment through drowsiness.
• I can just refuse the test — refusing a test without a valid reason can be a separate offence. Confirm how to respond to detection and penalties through legal help.