A guide to stopping distances and how to drive safely in adverse conditions

We all want to drive as safely as we possibly can, and one of the most obvious things to get right is maintaining proper stopping distances when we are out and about driving. But what do we mean by proper stopping distances? And what are some of the external factors you should be taking into account when driving?  

Stopping distances 

Stopping distance is the measurement of how far it takes you to come to a complete stop when you need to suddenly brake. Most people know that you should give roughly three car lengths of distances between you and the car ahead of you in good conditions (and if your brakes are well-maintained). However, there are many additional factors you’ll need to keep in mind when deciding what is a safe distance to maintain, including speed, weather conditions, and how well-maintained your brakes are. 

Thinking distance and braking distance 

Stopping distance is broken up into two separate sections – the thinking distance and the braking distance. These are fairly self-explanatory, but just to make sure we’re all on the same page here, the thinking distance is the distance travelled while you ‘think’ or react, while the braking distance is the distance travelled from when you actually apply the brakes. 

A big factor that affects your thinking distance is speed. Obviously if you are traveling faster, then you’ll go further during that brief window where you are reacting to the sudden stopping in front of you. At 20 mph, your thinking distance will be around six metres, while at 70mph it jumps to 21 metres before your car even begins to stop.  

Speed, of course affects your braking distance as well. Taking the previous example into account, the braking distance at 20mph is again around six metres, taking your total stopping distance to 12 metres. At 70mph, the braking distance jumps all the way up to 75 metres! Combined with the thinking distance of 21 metres, the stopping distance for 70mph is 96 metres! And that isn’t even including additional factors. 

If you want some more information about specific speeds and their stopping distances, check out his handy infographic we have that outlines estimated stopping distances at various speeds in dry driving conditions, with well-maintained brakes.

Stopping distance chart illustrating estimated stopping distances at various speeds.

Wet conditions 

Wet weather conditions can have a drastic effect on your braking distance. It is generally advised that you give double the distance you normally would in dry conditions. That means you should be expecting a stopping distance of nearly 200 metres in wet weather at 70mph! 

Bad weather can affect your tyres’ grip on the road – which can in turn affect your overall stopping distance. Plus, poor visibility, caused by very heavy rain, can make your reaction speed slower. Wet brakes can also be less effective, so it’s worth using them lightly on rainy days and regularly to help them dry out.  

There’s a lot to consider when driving in adverse weather – but most importantly, drive carefully and always allow for more braking distance. 

Snow and ice 

If double the distance seems a bit extreme for wet conditions, then the recommendation for snow and ice is going to blow your mind. It is generally expected for you to travel 10 times further in snow and ice, so a stopping distance of 900 metres is required at 70mph. This is why it is so very important to not only give plenty of space in icy weather, but to also travel at much slower speeds. Taking almost a kilometre to stop at 70mph is not a viable option if you need to stop quickly! 

For more on driving in wintery conditions, check out our full guide for driving in snow and ice.

What can affect thinking distance?  

One of the most avoidable factors that can affect your reaction time is driving while tired. Research suggests that your reaction time is doubled when tired, doubling your thinking time and increasing your stopping distance hugely. Lack of sleep affects your attention. Awareness and reactions – that's why we recommend taking a break every couple of hours if you’re on a longer journey.   

You should also be completely focused on the road ahead. If you’re distracted by your mobile, in-car tech or even talking to your passengers, your reaction time will be affected – so keep this in mind.  

It is much worse when driving while impaired or under the influence. There is no recommended distance for this because the recommendation is to just not drive. If you drink, don’t drive. Get a taxi, ask a friend, or sleep in the car if you really have to. You put yourself and others at risk driving and drinking. 

What can affect braking distance?  

Many factors can affect your braking distance – for example, road conditions or weather conditions as we mentioned above. The condition of your car’s brakes will also play a vital role so it’s important to keep them in good working order.   

You should also keep an eye on your tyre pressure and tread. If your tyre tread reaches about 3mm, you can expect to travel further before stopping than with new tyres. Under- and over-inflated tyres can also increase braking distance.

Check out our key tyre safety checks guide for more on keeping your vehicle’s tyres need to be in roadworthy condition.

The Highway Code

If you want more information about stopping distances, you can always check out the Highway Code guide.  

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Image credit: Khunkorn Laowisit via Vecteezy