Prescribed concentration of alcohol offences
It is an offence for a person to drive or try to drive a motor vehicle if the concentration of alcohol in their blood is more than the prescribed limit.
What is the limit?
The general prescribed limit is 0.05 grams of alcohol per 100 mL of blood.
A special limit of 0.02 grams per 100 mL applies to drivers of:
• public vehicles such as buses and taxis
• vehicles carrying dangerous goods
• vehicles over 13.9 tonnes.
The limit for learner drivers and drivers holding provisional licences is zero.
Drinking while driving
It is also an offence to consume alcohol while driving a motor vehicle.
Ranges of alcohol concentration
Blood alcohol concentrations are described as special, low, medium and high, with each range carrying a higher penalty than the one below
Police have the power to require anyone driving or attempting to drive a motor vehicle to undergo a breath test (Road Transport (Safety and Traffic Management) Act s.13).
The test normally involves the police taking a sample of the driver’s breath using a device known as a Lyons Alcolmeter SD2.
When a breath analysis is required
If the breath test shows a reading of 0.05 (or 0.02 for special range drivers) or higher, the person is arrested and taken to a nearby police station or mobile van for a breath analysis.
If the analysis confirms that the driver has exceeded the limit, a court attendance notice is issued showing the amount by which the driver exceeded the limit at the time of the offence.
Refusing a test
It is an offence to refuse to undergo a breath analysis. Failure to provide a sufficient sample is regarded as a refusal and is therefore an offence.
The police usually allow a driver two or three attempts to give a sample before charging them.
When police cannot administer a breath test or analysis
There are some restrictions on the powers of the police in relation to breath tests and analyses. They may not ask a person to undergo a breath test or breath analysis if:
• the person is seriously injured and the test may be dangerous
• the person is at home
• it is two hours or more since the person last drove or attempted to drive.
In these circumstances the police may still charge the person with driving under the influence of a drug or alcohol, but not with a prescribed concentration of alcohol offence.
In most circumstances a person over 15 who is admitted to hospital after an accident is required to undergo a blood test to determine their blood alcohol level (s.20).