In this fact page we will cover:
- the effects of alcohol on driving
- the drink-driving laws in the UK
- the penalties for drink-driving in the UK
- how to assess your fitness to drive
How alcohol affects your driving
Alcohol is a depressant and even small amounts (such as half a pint of lager) affect reaction times, judgement and co-ordination. Alcohol also makes you drowsy and affects vision and how you judge speed and distance.
Drivers who drink-drive are also not able to assess their own impairment because alcohol creates a false sense of confidence. This means that drivers are more inclined to take risks and believe they are in control when they are not. For these reasons, the only way for drivers to be safe is to not drink anything at all before driving: feeling sober is not a reliable indication that you are safe to drive.
If you’re driving, it’s better to have none for the roadStatement from the Government's Think! campaign
The law and the limits of drink-driving in the UK
In England and Wales, it’s legal to drive with a blood-alcohol concentration (BAC) of 80 milligrams of alcohol per 100 millilitres of blood (80mg/100ml). This is the highest limit in Europe.
In most of Europe, including Scotland, the blood alcohol limit is 50mg/100ml, and in many countries it is even lower. For example, in Sweden, the legal limit is 20mg/100ml for all drivers – effectively zero tolerance – while Hungary, Romania, Slovakia and the Czech Republic do not allow drivers to drink any alcohol at all.
There is no failsafe way to tell how much alcohol will put you over
the limit, or to convert the BAC limit into how many units you can have:
the concentration of alcohol in blood depends on various factors. These
include your weight, age, gender, or how much you have eaten before
drinking. That’s why the only safe amount to drink if you’re driving is nothing at all – not a drop.
In the UK if a driver is found to be over the drink-drive limit, and/or driving while impaired by alcohol, they can receive a maximum penalty of six months in prison, an unlimited fine and an automatic driving ban of at least one year.
Drink-drive rehabilitation courses
Drivers who have been found guilty of drink-driving and who have been banned for 12 months or more may be offered the chance to take a rehailitation course to reduce their driving ban
High-risk offenders are drivers who:
- were convicted of 2 drink driving offences within 10 years
- were driving with an alcohol reading of at least 87.5 microgrammes of alcohol per 100ml of breath, 200mg of alcohol per 100ml of blood, or 267.5mg of alcohol per 100ml of urine
- refused to give the police a sample of breath, blood or urine to test for alcohol
- refused to allow a sample of your blood to be tested for alcohol
These offenders need to pass a medical examination with a DVLA appointed doctor to prove their fitness to drive, prior to receiving a new licence.
Causing death while under the influence of alcohol
If a driver kills someone while under the influence of alcohol, they can be charged with causing death by careless driving while under the influence of drink or drugs (Section 3A of the Road Traffic Act 1988 (as amended by the Road Traffic Act 1991, section 3)), which carries a maximum penalty of 14 years in prison and an unlimited fine.
How to assess your fitness to drive
To be safe, drivers should ensure they are completely sober before driving – including the following day.
There’s no way of knowing exactly how long it takes to sober up
completely after drinking, but it’s longer than many people think. As a
rough guide, drivers should allow at least one hour to absorb alcohol,
plus at least one hour for each unit consumed – but it can take
longer, so it’s wise to leave extra time to be safe.
For example, if you finish drinking three pints of strong lager or
one bottle of 12% ABV wine (both nine units) at midnight, you will not
be rid of alcohol until at least 9am. If you have a heavy and/or late
night drinking you could be impaired all of the next day. Drinking
coffee, eating, sleeping and showering don’t make you sober up any
faster. It just takes time.
How long it takes for alcohol to leave your system varies depending on lots of factors, including:
- Gender – men tend to process alcohol faster than women;
- Dehydration – if you haven’t drunk enough fluids, alcohol will stay in your system for longer;
- Mixers – mixing drinks with water and juice means you absorb alcohol slower, fizzy mixers mean you absorb alcohol faster than with no mixers;
- Tiredness – when you’re tired your liver becomes less efficient, processing alcohol more slowly so it stays in your system for longer. 
Brake advises people who need to drive the next day to limit themselves to one or two drinks.
The alcohol content of drinks is measured in units. A UK unit is eight grams (or 10 millilitres) of pure alcohol. Below is a list of some popular drinks and how many units they contain:
- A single shot (25ml measure) of 40% spirit (e.g. gin, whisky or vodka): one unit
- A pint of 4.5% beer: 2.3 units
- A large (250ml) glass of 13% wine: 3.2 units
- A pint of 6% cider: 3.4 units