1.3.2 Blood alcohol concentration (BAC)
Blood alcohol concentration is the quantity of alcohol in the body. It is measured by the
weight in grams of alcohol present in 100 millilitres of blood. A person’s BAC can be
determined by analysing a blood, breath or urine sample.
As soon as you start drinking, your bAC begins to rise and could take up to two
hours to reach its highest concentration, especially if you have eaten a substantial meal
at the same time. Even though you may not have had a drink for an hour or more, your
bAC may still be rising.
1.3.3 What is the legal limit?
The amount of alcohol you are allowed to have in your body when you are driving will
depend upon the type of vehicle(s) you are authorised to drive and the current status
of your licence.
The following information sets out the various BAC limits and when they apply. Refer
to Appendix 3 for details of drink driving penalties. Drivers and riders should be aware
these penalties may change from time to time.
• novice drivers
• taxi drivers*;
• drivers of passenger vehicles with capacity to carry more than 12 adult
passengers*;
• drivers of omnibuses*;
• drivers of certain heavy vehicles*;
• drivers of vehicles carrying dangerous goods*;
• extraordinary licence holders; and
• recently disqualified drivers;
* The zero bAC limit for certain drivers may not apply at all times. please visit
www.transport.wa.gov.au/dvs for further information on when a driver must have a
bAC limit of zero.
0.02 BAC applies to:
• Drivers who hold a provisional licence that are no longer Novice Drivers.
0.05 BAC applies to:
• All other drivers.
1.3.4 How much alcohol takes you over the legal limit?
0.00 per cent BAC
You must not drink any alcoholic drinks at all if you intend to drive
0.02 per cent BAC
To be sure that you do not reach 0.02 per cent, you should not drink any alcoholic
drinks at all when you intend to drive.