Zero BAC and Roadside Drug Testing for Heavy Vehicle Drivers

Zero BAC for Heavy Vehicle Drivers

Victoria imposes a strict 0.00 blood alcohol concentration (BAC) limit on drivers of heavy vehicles with a GVM over 4.5 tonnes, and on drivers of commercial buses, taxis, hire cars, and emergency vehicles. The general driver limit of 0.05 does not apply to you once you are behind the wheel of a heavy rigid truck. The 0.00 rule covers the full time you are driving, in charge of, or occupying the driver's seat of the vehicle — including while parked with the engine running.

The rationale is straightforward: alcohol impairs reaction time, hazard perception, and judgement at any concentration, and the kinetic energy of a loaded rigid truck multiplies the consequence of any impairment. A heavy rigid at 80 km/h carries roughly 3.5 megajoules of kinetic energy per tonne of mass; impairment that adds a half-second of reaction time can add 11 metres of stopping distance, often the difference between a near miss and a fatality.

Penalties for a Zero BAC Breach

A heavy vehicle driver detected with any alcohol above 0.00 faces:

• Immediate licence suspension at the roadside if the reading is 0.05 or above, or on a second reading in some cases
• Licence cancellation for a minimum period (typically 6 months for a first offence at 0.05-0.07, longer for higher readings or prior offences)
• Heavy fines set by the Road Safety (Drivers) Regulations and indexed annually
• An alcohol interlock condition imposed on relicensing, typically for at least 6 months, requiring a zero reading before the engine will start
• Demerit points on any subsequent offence

A first offence at a reading between 0.00 and 0.05 for a heavy vehicle driver is still a breach of the 0.00 limit — the limit is zero, not a tolerance band.

Roadside Drug Testing

Victoria Police conduct roadside saliva (oral fluid) testing for three substances:

The roadside test is administered with an absorbent swab placed in the mouth or against the tongue. A preliminary result is typically available within a few minutes. A positive preliminary result triggers a second oral fluid sample taken at the roadside or at a drug bus, which is sealed and sent to a laboratory for confirmation. The driver is generally prohibited from driving until the laboratory result is returned — a negative lab result clears the driver; a positive result becomes the basis for charges.

What the Law Prohibits

It is an offence in Victoria to:

• Drive, or be in charge of, a motor vehicle with any of the three prescribed illicit drugs present in your oral fluid or blood
• Refuse a roadside drug test or a breath test (refusal is treated as a serious offence with penalties equivalent to a high-range drink driving)
• Fail to stop at a drug or alcohol testing station when directed by police

The drug presence offence is a strict-liability offence — the prosecution does not need to prove impairment, only presence. Unlike alcohol, there is no graduated threshold; any detectable amount of the three prescribed drugs is an offence.

Prescription Medicines and the Zero BAC Trap

A common trap is the interaction between lawful prescription medicines and the drug-driving rules. Some prescribed and over-the-counter medicines can produce a positive oral fluid result:

• Some ADHD and narcolepsy medications (amphetamine-class stimulants) can register as methamphetamine
• Some codeine-containing pain relievers historically produced false concerns, though codeine itself is not a prescribed drug for testing — check current rules
• Some cannabis-based medicines prescribed under authorisation can register as THC

Drivers must declare any medical condition to VicRoads and seek medical advice on whether a prescribed medicine will affect their ability to drive or risk a positive test. The defence of "I had a prescription" does not automatically defeat a drug presence charge in Victoria for the three prescribed drugs — the offence is presence, not source. Carry a copy of any current prescription and discuss with a lawyer if charged.

Worked Scenarios

Chain of Responsibility and Employer Duties

Under the Heavy Vehicle National Law as applied in Victoria, operators and schedulers have a positive duty not to cause or encourage a driver to breach road transport laws, including fatigue and fitness-to-drive rules. An operator who schedules a driver knowing the driver has consumed alcohol or has used a prescribed drug, and who permits the driver to drive, can be charged under Chain of Responsibility provisions. The driver's 0.00 BAC and drug-free obligation runs in parallel with the operator's duty — both can be prosecuted for the same breach.

Common Exam Traps

• The 0.00 limit applies whenever you are in the driver's seat of a heavy vehicle, including while parked with the engine running for a break.
• "One beer then drive the truck home" is a breach — there is no tolerance band, the limit is zero.
• Refusing a breath or saliva test is itself a serious offence with penalties equivalent to a high-range reading; it is not a way to avoid a charge.
• A prescription is not an automatic defence to a drug-presence charge for the three prescribed drugs; presence is the offence, not source.
• The three prescribed drugs are methamphetamine, THC, and MDMA — other drugs (e.g. cocaine, ketamine) are not covered by the Victorian roadside oral fluid program but may be detected in blood tests following serious crashes.
• A positive preliminary result triggers a second sample sent to a laboratory; the driver is generally prohibited from driving until the lab result is returned.