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A guide to stopping distances

calendar Published on: Monday, 21st January 2019 | female icon Author: Aminta Gagnon

Stopping distances are something that all learner drivers have to familiarise themselves with in order to pass their theory tests. Unfortunately though, this information is something that many of us quickly forget once we get our licences. In fact, the bad habit of following other vehicles too closely (which is known as tailgating) is one of the main causes of road accidents in the UK.

To help you stay safe behind the wheel, here is a brief guide to stopping distances - including what they are, how to remember them and the steps you can take to minimise them.

Average stopping distances

Stopping distances are calculated by adding the time it takes you to realise you need to brake (known as your ‘thinking distance’) to the time it takes your car to stop once the brakes have been applied.

Guidelines provided by the Highway Code suggest that minimum stopping distances are as follows:

?    20mph – 12 metres

?    30mph – 23 metres

?    40mph – 36 metres

?    50mph – 53 metres

?    60mph – 73 metres

?    70mph – 96 metres

These figures are based on a driver reaction time of 0.67 seconds, which assumes that people are concentrating and alert. However, research findings revealed by road safety charity Brake suggest that reaction times could actually be much longer than this. The study calculated an average thinking time of 1.5 seconds.

Taking road conditions into account

It’s also important to take road conditions into account when calculating stopping distances. For example, if the surface of the highway is wet or icy, it will take you longer to bring your car to a halt. Anything that limits the amount of friction between your tyres and the road makes it more difficult to stop, so you should factor this in when driving.

Research suggests that braking distances can double in wet conditions and go up tenfold if it’s snowy or icy. Other road-related factors can impact on your ability to stop quickly too. For instance, oil spills or loose surfaces like gravel will mean your tyres lose traction.

Applying the 'two second rule'

When you’re travelling, doing complex calculations about how much space you need to leave between your car and the vehicle in front isn’t realistic. However, there are much simpler ways to work out if you’re leaving enough room to stop safely. For example, the ‘two second rule’ is a good maxim to follow in dry conditions. It means choosing a fixed point ahead of you on the road and registering when the vehicle in front of you passes it. From this time, two seconds or more should pass before you get to the same location. If this happens, you’ll probably have enough time to stop suddenly if you need to.

How to minimise your stopping distance

As well as being aware of average stopping distances and taking them into account when driving, there are steps you can take to help you brake more quickly and effectively. Some of these relate to your car and some to your habits behind the wheel.

In terms of your vehicle, it’s important to make sure your tyres are up to scratch. For example, choosing good quality new tyres when you need replacements will help. It’s also important to keep an eye on tyre tread. By law, your tyres must have tread that’s at least 1.6mm deep, but experts suggest you should get replacements before you reach this level. Tests conducted by the engineering and testing consultancy MIRA found that compared to a tread depth of 6.7mm, stopping distances at 1.6mm were 44.6 per cent greater on smooth concrete and 36.8 per cent greater on hot rolled asphalt. Generally speaking, experts suggest that you should replace your tyres once the tread falls below 3mm. Check your tyre pressure regularly too. Keeping your tyres inflated to the correct level will help to maximise their contact with the road and therefore reduce your stopping distances.

It’s also essential to maintain your brakes effectively, and this includes making sure your brake pads are replaced before they get too worn down.

When it comes to your driving habits, one of the most important things you can do is to always be alert. Being tired slows your reaction speed down and can make collisions much more likely. So, avoid getting into the driving seat if you’re feeling sleepy, and make sure you plan regular breaks on long journeys. It’s advisable to take a 15-minute break every two hours. Staying hydrated also helps to keep you focussed.

Another tip is to avoid distractions while you’re on the move. This could be anything from adjusting your sat nav to looking at your mobile phone. Taking your eyes off the road even for a second or two can prevent you from spotting a hazard and braking in time.

Ensuring good visibility in your car will help you to minimise your reaction time too. For example, by making sure you always have plenty of windscreen washer fluid and keeping your wiper blades in good condition, you will be able to keep your windscreen clear and therefore see and react to potential dangers more effectively. Also, if it’s icy, make sure you clear your car windows thoroughly before you set off on a journey.

By ensuring you’re up to speed on the topic of stopping distances and taking measures to keep your thinking and braking distances to a minimum, you stand a better chance of staying safe on the roads.