All you need to know about breathalysers | Western Cape Government

All you need to know about breathalysers

2015
(Western Cape Government)

Drinking and drivingDriving after you've been drinking alcohol is a bad idea, as you may be over the legal drinking limit.

The last thing you want is to fail your breathalyser test, pay a fine or get arrested and risk losing your driver’s licence.


It is illegal to drive under the influence of alcohol or narcotic drugs. The maximum blood alcohol limit for drivers is 0.05g per 100ml of blood.

As a rough guide, this means you are able to drink a maximum of one unit of alcohol per hour, which is of 10ml of pure alcohol, as your body can only process one unit of alcohol per hour. If you weigh less that 68kg our body may need more time to process the same amount of alcohol. 

Remember: any amount of alcohol impairs your ability to drive safely, and different people react differently to alcohol. The best advice is to avoid alcohol completely if you are going to be driving.

What does one unit of alcohol really mean?

  • 1 x 75 ml glass of wine = 1 unit
  • 1 x 250 ml glass of wine = 3.3 units
  • 1 x shot/shooter = ½ unit in most instances
  • 1 x spirit cooler = about 1.25 units
  • 1 x beer = 1.5 units or possibly more
  • 1 x cider = 2 units
  • 1 x 25 ml tot of spirits = 1 unit
  • 1 x cocktail = Between 2 and 4 units

According to the Automobile Association (AA) “quick fixes” like drinking coffee or taking a cold shower are myths and should you be pulled over at a roadblock your breathalyser test may come back saying that you are over the legal drinking limit.

What the law says

Any person driving on our roads needs to be familiar with the laws regarding drunk driving, as stated in the National Traffic Act 1996. But the main points you need to remember are that: 

  • No person on a public road can be in the driver’s seat of a car, with the engine running, while under the influence of alcohol or drugs.
  • If the concentration of alcohol in your blood is more than 0.05g per 100 ml of alcohol, you are not allowed to be sitting in the driver’s seat of any vehicle while the engine is running.
  • According to the National Traffic Act of 1996, "if in any prosecution for a contravention of the provisions of subsection (2), it is proved that the concentration of alcohol in any specimen of blood, taken from any part of the body of the person concerned, was not less than 0.05g per 100ml at any time within two hours after the alleged offence, it shall be presumed, until the contrary is proved, that such concentration was not less than 0.05g per 100ml of blood at the time of the alleged offence".

What are the consequences?

In South Africa if you are caught under the influence of alcohol or drugs while driving, you could go to prison and have a criminal record for the rest of your life. The worst case scenario is that you could be involved in a car crash and should someone die, you could be charged with culpable homicide.

You could also be liable to pay a fine. Fines can go up to R120 000 and you also stand the risk of having your driver’s licence suspended.

Remember that if you are pulled over at a roadblock and are suspected of being over the legal drinking limit, you may not refuse to have any blood taken or a breathalyser test.

Tips from the AA

  • One in every 15 drivers on the road in the evening is over the limit.
  • More than half of all pedestrians killed last year had been drinking.
  • Morning rush hour bumper bashings are most likely a result of the previous night's drinking.
  • The cost of crashes to the economy in 2008 was estimated at R48 billion.
  • Remember a sober driver is best. If you are hosting a party, offer to accommodate your guests overnight.

Report all drunk driving and traffic incidents to your nearest police station immediately.

The content on this page was last updated on 9 April 2015