The effects of alcohol on both physical and mental functioning make driving hazardous—alcohol is involved in around one-third of all road deaths.
The risk increases with the amount of alcohol in the bloodstream. For this reason it is against the law to drive with a blood alcohol concentration over a prescribed limit.
Blood alcohol concentration is measured in grams per 100ml (g/100ml)
- For most fully licensed drivers, the limit is 0.05.
- For drivers with a learners or provisional licence—L or P-plate drivers—the limit is zero.
- For people driving heavy vehicles or public passenger vehicles— trucks or buses—and people driving vehicles containing dangerous goods, the limit is 0.02
The amount of alcohol that can be drunk before a person reaches the legal limit varies considerably from one person to another, and for the same person in different circumstances. Generally speaking, a guide for keeping below the 0.05 limit is:
- for men, no more than two standard drinks in the first hour of drinking, and no more than one per hour after that
- for women, no more than one standard drink in the first hour of drinking, and no more than one per hour after that.
Learner and provisional licence holders should not drink at all if they intend to drive.
Driving with a blood alcohol concentration over the legal limit is a serious offence. A drunk driver who causes the death or injury of another road user can face criminal charges, with possible imprisonment if convicted.