Stopping Distances


Driving after drinking alcohol is dangerous. It:

  • Gives a false sense of confidence
  • Slows reaction times
  • Reduces co-ordination
  • Reduce the ability to judge speed, time, and distance
  • Reduces concentration
  • Increases fatigue
  • Impairs judgement

This greatly reduces a driver's ability to drive safely, and puts them and others in serious danger. On average, 5 people are killed in drink drive crashes every week on Britain's roads. Often it is an innocent person (passengers, people in other vehicles, pedestrians, motorcyclists and pedal cyclists) who suffers, not the driver who is over the drink drive limit.

The level of drink driving has reduced substantially over the last few decades. In 1980, almost 1,500 people were killed, and nearly 8,000 people were seriously injured, in drink drive crashes. In 2016, this had fallen to 240 deaths and 1,260 serious injuries. However, this still means that around 5 people are killed and 24 seriously injured by drink drivers every week. Despite the long term reduction, drink drive deaths and injuries have not changed very much over the last few years.

The Law

It is a serious criminal offence to drive a motor vehicle if you are above the drink drive limit.

In England and Wales, the drink drive limit is 80mg alcohol per 100ml blood.

In Scotland, the drink drive limit is lower, at 50 mg alcohol per 100ml blood.

In Northern Ireland, the drink drive limit is 80mg alcohol per 100ml blood, but is due to be reduced to 50 mg for most drivers, but to 20 mg for young drivers and professional drivers.

In 2016, 463,319 breath tests were carried out by the police, the lowest number since data collection began in 2002, and the first time the number of breath tests had fallen below half a million in a single year. The drink drivers faced a driving ban of at least 12 months, a large fine and possible imprisonment.

It is almost impossible to judge whether you are above or below the limit, and so the best advice is always to have none for the road.

The speed with which alcohol is absorbed into the bloodstream varies depending on a person's size, age, weight, gender and whether they have eaten. It takes about an hour for 1 unit of alcohol to be removed by a healthy liver. The exact number of units of alcohol in a drink depends on its size and alcoholic strength by volume (abv). For example, a 175ml glass of wine of 12%abv would be 2.1 units, and a 250ml glass of the same wine would be 3 units.

Morning After

Many drink drivers are caught the morning after they have been drinking. As it takes several hours for alcohol to disappear from the body, someone who was drinking late the previous evening, could easily still be over the limit on their way to work the next morning. Even if under the limit, they may still be affected by the alcohol in their body.

Drugs and Medicines

It is also illegal to drive while unfit to do so due to drugs or medicines. Around 55 people are killed each year in accidents involving drivers who were impaired by drugs (including legal drugs), over 250 are seriously injured and around 750 slightly injured. This is likely to be an under-estimate.

It is also an offence to drive, attempt to drive, or be in charge of a motor vehicle with certain drugs in the body above a specified limit. This applies to illegal drugs, prescribed medications and over-the-counter medicines.

The law sets very low limits for eight illegal drugs, such as cannabis, cocaine, ecstasy and ketamine, so taking even a very small amount could put a person over the limit. It also sets limits for eight prescription drugs (cloanzepam, diazepam, flunitrazepam, lorazepam, oxazepam, temazepam, methadone and morphine), but the limits are higher than normal prescribed doses. Anyone taking a medicine under the advice of a healthcare professional should check with them that they will not exceed the limit.

The Police conduct roadside tests to help them assess whether a driver may be impaired.

Alcohol and Drugs

Mixing alcohol and drugs together is even worse as their effects combine. Even low levels of alcohol mixed with low levels of drugs cause significant impairment.

The Penalties

The penalties for drink driving, drug driving and driving while unfit through drugs are a:

  • Minimum 12-month driving ban
  • Criminal record
  • Substantial fine or up to 6 months in prison or both

Other consequences can include losing your job loss, losing independence, higher car insurance when you get your licence back and trouble getting into countries like the USA. Of course, the ultimate penalty could be having to live with injuring or even killing another person.

The Simulator and Drink Driving

The simulator allows you to compare the stopping distances at different speeds, with or without alcohol in the driver's body ticking the alcohol box.

A car's overall stopping distance is made up of the driver's thinking distance (the distance the car travels from the point when the driver realises they need to brake and they actually start to brake) and their braking distance (the distance the car travels from the point when the driver starts to press the brake pedal and the vehicle comes to a complete stop).

Alcohol increases the time it takes drivers to process information, which increases their thinking and stopping distances. A drunk driver who spots a pedestrian would take vital extra moments before applying the brake.

This is shown in the simulator by the significant increase in the thinking distance, but in the real world a drunk driver may also not press the brake as hard as a sober driver, which may also increase their braking distance.

The extra time it takes a driver to press the brake, means that the driver is more likely to hit the pedestrian, rather than stop in time, and the vehicle is travelling at a faster speed when it hits the pedestrian, causing a more severe injury.