November 5, 2020

Drugs and driving

police and drug buses

Drug driving is a serious road safety issue.

“One in four Victorians who use drugs admit to driving under the influence of illicit substances.” 1

When you drive under the influence of alcohol or drugs (including some prescription and over-the-counter medications) you pose a danger to yourself, your passengers, and others on the road.

Within the last five years, approximately 41% of Victorian drivers and motorcyclists who died on the roads and were tested had drugs in their system.1 Cannabis and stimulants were the most commonly detected.1

How drugs impact your driving

Even in low doses, drugs can significantly reduce your driving skills.

If you’ve taken cannabis, you may drive too slowly, find it difficult to stay awake, or find it hard to stay within designated lanes.1 2

Stimulants, like amphetamines and cocaine, can lead to speeding or erratic driving as well as increased risk taking behind the wheel.1

Prescription medication

If you take prescription medication, whether it has been prescribed to you or not, be aware of the potential driving risks.

If you're feeling drowsy, aggressive, dizzy, nauseous, light-headed or shaky, it can be dangerous to drive as this may impair your vision and ability to concentrate.

If taking prescribed or over-the-counter medication, always:

  • read the labels carefully and obey the directions and warnings
  • ask a doctor or pharmacist if it’s likely to affect your driving
  • arrange alternative transport, if advised.1


Depressant drugs (such as alcohol and benzodiazepines) opioid drugs (such as heroin and oxycodone) and cannabis can all ‘depress’ or ‘slow down’ activity in the central nervous system.

Combining different depressants or opioids can multiply this effect and lead to:

  • reduced reaction times
  • reduced concentration
  • drowsiness
  • difficulty processing information
  • difficulty doing more than one thing at a time (e.g. keeping your car within its lane while watching for oncoming traffic).


Stimulant drugs, such as amphetamines and cocaine, ‘speed up’ the activity of the central nervous system.

Combining different stimulants can multiply this effect, putting greater stress on the body, particularly the heart and other vital organs, and can lead to:

  • attention difficulties
  • tendency to fidget
  • aggressive and dangerous driving
  • increased risk taking
  • over-confidence in driving skills.


Psychedelics, such as LSD, magic mushrooms and mescaline, distort a person's perception of reality. MDMA and cannabis may also have some hallucinogenic effects.

Taking these drugs can lead to seeing or hearing things that aren't really there or experiencing real things in a distorted way.

The effects of psychedelics vary and combining two or more drugs of this type can have unpredictable effects on driving ability.

As a general guide, some of the effects of psychedelic drugs include:

  • hallucinations
  • confused thinking
  • blurred vision
  • reduced coordination.

The risks of combining drugs

The impact of mixing different types drugs can be unpredictable – it’s often difficult to know how combinations of drugs will interact and how people will be affected.

This includes the mixing of illegal and legal drugs, as well as combinations of legal drugs such as drinking alcohol while taking over-the-counter or prescription medication.

The risk of having a crash while under the influence of two or more drugs is high.

For example, if alcohol and cannabis are used together, a person will become more impaired at a quicker rate than if using either one on its own.3

Combining drugs that have different effects also reduces coordination, hindering your ability to drive. Some examples include mixing alcohol with MDMA, or cocaine with benzodiazepines.

If you’ve been drinking alcohol and using amphetamines, you may not feel the depressant effects of the alcohol, as it's masked by the stimulant effects of the amphetamines.

You may feel capable of driving, but in reality—you might be intoxicated. In Australia, it’s not legal to drive if your blood alcohol level is over 0.05.

If you use drugs, the safest option is not to drive.

Drugs and driving – things to remember

  • Alcohol and other drugs can affect you long after the immediate impact of the substances appears to have worn off. People with drugs in their system continue to pose a higher road risk, even if they feel it’s safe to drive.4 People may also feel tired or hungover as drugs wear off, which can also impair their driving ability.
  • All drivers, whether young or old, should avoid driving if they've recently consumed alcohol or other drugs.
  • Speak to a health professional and read the packaging information or a Consumer Medication Information sheet (CMI) before mixing medications, alcohol or other drugs.
  • Tell your doctor about all the drugs that you use (including prescribed, over-the-counter and illegal drugs). They can help minimise the risk of unwanted interactions between drugs.

Plan ahead: safe transport

If you're going to consume alcohol or other drugs, including prescription medications, plan ahead to reduce the risk of dangerous driving. Alternative transport options include:

  • organising a driver who won't have drugs in their system
  • arranging a friend or family member to pick you up
  • using public transport or a taxi
  • staying overnight.

Remember, drugs can continue to affect you the next day and tiredness, hangovers and 'coming down' can impact your ability to drive safely.

More information on safe driving:

Medications and fitness to drive

Roadside drug testing

Blood alcohol levels

Young drivers: information for parents

Information for commercial drivers

Read more evidence on the ADF Library

  1. Transport Accident Commission. Drug driving n.d. [21.10.2020].
  2. Stough C, King R. Drugs and drving 2010 21.10.2020.
  3. Mallick J, Johnston J, Goren N, Kennedy V. Drugs and Driving in Australia: a survey of community attitudes, experience and understanding Melbourne: Alcohol and Drug Foundation 2007
  4. Monash University Accident and Research Centre.Going Solo 2007 [21.10.2020].

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