Drug driving is an increasing road safety problem. There is a particularly strong association between drug use and crash involvement, with accident risk estimated to equal that of a driver with a blood alcohol concentration of 0.1 to 0.15%.


  • Research demonstrates that an alarming number of motorists are driving after consuming illegal drugs  and the occurrence of drug driving in some groups may be greater than drink driving.2
  • A 10 year evaluation of road crashes in Australia estimated that 1 in 4 drivers killed in road crashes tested positive to drugs other than alcohol.3
  • Drug driving is a contributing factor in approximately 7% of road fatalities in Australia.

How do drugs affect me?

  • Many drugs can affect our ability to drive safely.
  • These drugs include illegal (illicit) drugs, as well as legal drugs such as alcohol and medicines (prescribed and over-thecounter).
  • Drugs that affect driving include cannabis, amphetamines, benzodiazepines, hallucinogens, antihistamines and opiates.
  • The most commonly used illegal drugs are marijuana followed by speed and ecstacy.5
  • Many drugs are highly addictive to the extent that users need them in order to function in their daily routine.  Excessive  drug use can cause cognitive  impairment, which can affect judgement,  memory and reaction time.
  • The time it takes to remove drugs from the body can impinge on work and driving performance. An individual can consume drugs in the evening and still have drugs present in his or her body the next day.
  • The level of drugs which will remain in a person’s system over time can depend on a range of factors including the strength of the drug, if it was taken in combination with other drugs, the situation in which it was used and the individual’s metabolism.

Drug use can affect drivers and the driving task by:

  • slowing down the reaction time – this can be crucial in an emergency situation.
  • dulling the thinking process making it difficult to multi-task – an essential skill necessary for safe driving.
  • causing a distorted view of time and distance – reducing your ability to drive safely and identify driving hazards.
  • stimulating the nervous system – leading to:
    • reduced attention span – not   noticing other drivers and/or  vehicles.
    • over-confidence in driving skills that  is not supported by an actual  improvement in driving ability.
    • aggressive and dangerous driving.
    • the sudden onset of fatigue as the  stimulant effects wear off.
    • altering their view and experience of  reality, with their actions and  responses quite different to what is  actually needed.  They may be  unaware of how much their driving  skills are impaired.

Can I have a small quantity of drugs and still drive?

Illegally manufactured drugs vary in strength and purity. This makes it difficult to predict the extent to which a person’s driving skills will be impaired.  Often drugs are consumed in combination, or with alcohol, and the impairment to driving ability can be much greater.  Severe penalties apply to anyone caught driving under the influence of illegal drugs.