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What is the legal drink drive limit?

• 80 milligrammes (mg) of alcohol per 100 millilitres (ml) of blood (80mg/100ml), or
• 35 microgrammes of alcohol per 100ml of breath, or
• 107mg of alcohol per 100ml of urine

The limit has remained unchanged since its introduction by the Road Safety Act 1967, which also gave the police powers to breath-test drivers suspected of drink driving.

What are the current penalties?

For exceeding the legal alcohol limit for drivers:

• up to 6 months in prison
• a fine of up to £5000
• a minimum of 12 months' disqualification (3 years for a second offence within 10 years)

The rate alcohol is absorbed into your blood depends on factors including:

• Gender
• Age
• Body build and metabolism
• Whether you’ve eaten
• Whether you’re tired, stressed or unwell

This means that there is no reliable way to know whether you’re safe to drive after having a drink.  And don’t forget, if you’ve been merry the night before, you might be still over the limit the morning after.

How much is a unit?

A unit of alcohol is 10ml of pure alcohol.  However, the alcoholic content in a drink is usually expressed as a percentage of the drink's volume - which means that your mental maths can need to be pretty spot on to work out exactly how much you've had.

It's also difficult to know exactly how many units you've had to drink - not only are wines, beers, largers and spirits all different strengths, but if you're drinking in a pub or bar, a serving isn't always the same size. 

This is why the SSRP's advice is not to risk it at all.  Take public transport, nominate a named driver or save your drinking until you know you don't have to drive.

More information about alcohol units can be found on the DrinkAware website, as can a useful unit calculator.