Drink driving and the legal alcohol limit

• The law on drink driving
• Staying under the limit
• How alcohol affects driving
• How would I be tested for drink driving?
• What happens if I'm caught drink driving
• How to ensure you don't drink and drive

In 2010, nearly 10,000 reported road casualties happened when a driver was over the legal alcohol limit. As a result, 250 people were killed in drink driving accidents (1).

These figures are too high but accidents involving drink driving have decreased hugely over the last 30 years. Deaths and serious injuries related to drink driving have fallen by more than three-quarters since 1980 (2). 

What's the law on drink driving?

In the UK, the alcohol limit for drivers is 80 milligrammes of alcohol per 100 millilitres of blood, 35 microgrammes per 100 millilitres of breath or 107 milligrammes per 100 millilitres of urine. In most other European countries, the limit is less, usually 50 milligrammes per 100 millilitres of blood (3).

How much can I drink and stay under the limit?

There is no fool-proof way of drinking and staying under the limit. The amount of alcohol you would need to drink to be considered over the driving limit varies from person to person. It depends on: (4)

• your weight
• your gender (men tend to process alcohol faster than women) 
• your metabolism
• your current stress levels
• whether you've eaten recently 
• age (younger people tend to process alcohol more slowly

Even small amounts of alcohol can affect your ability to drive so the only safe advice is to avoid any alcohol if you are driving.  

What is a unit of alcohol? Find out here...

How alcohol affects driving

Many of the functions that we depend on to drive safely are affected when we drink alcohol: 

• the brain takes longer to receive messages from the eye
• processing information becomes more difficult
• instructions to the body's muscles are delayed resulting in slower reaction times.

You can also experience blurred and double vision, which affects your ability to see things clearly while you are driving. And you’re more likely to take potentially dangerous risks because you can act on urges you normally repress (5).

How would I be tested for drink driving?

Even small amounts of alcohol affect your ability to drive and the only safe advice is to avoid any alcohol if you are driving.

If the police want to investigate whether you are over the drink driving limit, they will carry out a screening breath test at the roadside. To do this, they will use a breathalyser.

If you fail this test, or if they have other grounds to believe that your driving was impaired through drink, you will be arrested and taken to a police station.

At the station you will need to provide two more breath specimens into a complex breathalyser, called an evidential breath testing instrument. The lower of the two readings is used to decide whether you are above the drink driving limit.

If the evidential breath sample is up to 40% over the limit you have the right to replace your evidential breath specimen with blood or urine - the police officer will decide which test you will have. If your evidential samples show that you are over the limit, you will be charged.

The police can carry out a breathalyser test if you have committed a moving traffic offence (such as banned turns) been involved in an accident, or have given the police grounds to believe you are over the limit.

The police are allowed to stop any vehicle at their discretion, and will often set up drink driving check points over periods such as Christmas and New Year’s Eve.

What’s the punishment if I get caught drink driving?

Anyone caught over the legal alcohol limit when driving will be banned from driving for at least 12 months, and fined up to £5,000. You can also be sent to prison for up to six months. Imprisonment, the period of disqualification and size of fine depend on the seriousness of the offence (6).

If you’re caught drink driving more than once in a 10 year period, you’ll be banned for at least three years.

How to ensure you don't drink and drive

• Arrange within your group of friends who's going to be the designated driver. A designated driver is the person who abstains from alcohol on a night out so they can drive the rest of their group of friends home safely.
• If you live somewhere with good public transport links – take advantage of them. If you’re planning on staying out beyond the last train, tube or bus, make sure you’ve got a couple of taxi numbers. 
• If you have no option but to drive, stick to zero alcohol beers, mocktails or standard soft drinks. 
• Not every night out has to involve a bar or pub - book a table at a restaurant or try one of our alcohol-free nights on the town ideas.

More information on drink driving:

• Is it safe to drive the morning after drinking?
• Think! Road Safety campaign website
• The Institute of Alcohol Studies’ factsheet on Drinking and Driving
• Directgov - information on drink driving penalties 
• Alcohol and accidents