Laws on drink and drive units in the UK explained

DRIVING under the influence of alcohol is illegal in the UK, and anyone found guilty could be handed a serious penalty.

Because of the ways in which alcohol can affect a person’s driving, there are strict rules on how many drinks you can have and still legally be able to drive. Here’s what we know.

How many units of alcohol can you have before driving?

The drink driving limit in the UK is measured in milligrams rather than units.

The limit is 80 milligrams in every 100 millilitres of blood.

This roughly translates to four units of alcohol for men and three units for women, but this is not a one-size-fits-all rule.

Are there illegal baby names? Surprising monikers that are BANNED in other countries, from Sarah to Thomas

Body mass, gender and how quickly the body absorbs alcohol are major factors on how each individual is impacted by drinking.

Generally speaking, two pints of beer or two small glasses of wine is enough to put you over the legal limit.

The stronger your drink, the longer it takes to leave your system, so a large glass of wine (250ml) could be in your blood for four hours after drinking.

While a pint might take less time to leave your system (two hours instead of four), you should still factor in an hour for it to absorb into your body.

For example, if you have four pints and stop drinking at midnight, you will not be safe to drive until 9am.

Each person has their own limit because all bodies process alcohol differently.

But if you’re planning on driving, the easiest way to make sure you're on the right side of the law and safe behind the wheel is not to drink at all.

If you enjoy a night of drinking, you should still give yourself plenty of time the next day before hitting the road.

What is the drink driving limit in the UK?

The drink drive limit varies in the UK depending on the country.

There are different rules for motorists in England, Wales and Northern Ireland than for drivers in Scotland.

All about Rachel Nickell who was murdered in front of her son Alex Hanscombe

The limits for England, Wales and Northern Ireland are:

• 80mg of alcohol per 100ml of blood
• 35mg per 100ml of breath
• 107mg per 100ml of urine

In Scotland, the limits are:

• 50mg of alcohol per 100ml of blood
• 22mg per 100ml of breath
• 67mg milligrammes per 100ml of urine

The Scottish regulations mean that just one drink could put you over the limit.

Bear in mind that even if you are below the limit, one drink can still impair your driving skills and make getting in a car unsafe.

In fact, with just 10mg of alcohol per 100ml of your blood (one eighth of the limit in England and Wales), you are 37% more likely to be in a fatal accident than when completely sober.

For this reason it is best to avoid driving after consuming any alcohol — even if you think you can handle your drink.

How does alcohol affect driving?

Having alcohol in your system impairs your ability to drive safely as:

• The brain takes longer to receive visual messages from the eyes
• Processing information becomes slower
• Instructions to the body's muscles are delayed, resulting in longer reaction times
• Blurred or double vision affects the ability to see people, other vehicles and hazards clearly while driving
• Lowered inhibitions make drivers more likely to take potentially dangerous risks

Remember, drinking will cause all of these impairments, not just one.

All of these effects combined can result in dangerous driving.

What can affect the drink driving limit?

There are several factors that can impact how much alcohol is absorbed into your blood, and when it tips you over the limit.

These levels can be dependent on:

• Your weight, age, sex and metabolism (the rate at which your body uses energy)
• The type and amount of alcohol you have drunk
• How much you have eaten recently
• Your stress levels at the time

What is the penalty for drink driving?

The actual penalty a person gets depends on the offence and is up to the magistrates who hear the case.

Here are the maximum penalties handed out to drink drivers:

• Being in charge of a vehicle while above the legal limit or unfit through drink: Three months' imprisonment, up to £2,500 fine and a possible driving ban
• Driving or attempting to drive while above the legal limit or unfit through drink: Six months' imprisonment, an unlimited fine and a driving ban for at least one year (three years if you have been convicted twice in 10 years)
• Refusing to provide a specimen of breath, blood or urine for analysis: Six months imprisonment, an unlimited fine and a driving ban for at least one year
• Causing death by careless driving when under the influence of drink: 14 years imprisonment, an unlimited fine, a ban from driving for at least two years and an extended driving test before your licence is returned

Other complications include:

• A significant increase in the cost of car insurance
• Employers will see convictions on the licences of individuals who drive for work
• Trouble travelling to countries like the USA

When were roadside breath tests introduced?

The first roadside breath test was carried out 50 years ago, on October 8, 1967.

In the year the breathalyser was introduced there were 1,640 people killed in crashes attributed to alcohol, but publicans protested to then-Transport Minister Barbara Castle that the new law could put them out of business.

AA president Edmund King said: "The breathalyser sits alongside compulsory seat belts and the introduction of Euro NCAP crash testing as the three biggest road safety life-saving measures introduced in the last half-century.

"The breathalyser and subsequent campaigns saved thousands of lives and helped make drink driving socially unacceptable."