Understanding Stopping Distances
Ellie Dyer-Brown, 2 months ago
5 min read
- Brakes
- Car ownership
WhoCanFixMyCar explains everything you need to know about stopping distances.
Being aware of how long it will take your car to stop in different conditions is vital for the safety of you and other road users. This guide covers everything you need to know.
Contents
How do I work out stopping distances?
The stopping distance formula
You can work out vehicle stopping distances for different speeds by combining your braking and thinking distance.
BRAKING DISTANCE + THINKING DISTANCE = STOPPING DISTANCE
There's also a famous saying that can help you keep a safe distance from the car in front: "Only a fool breaks the two-second rule".
When the vehicle in front of you passes a particular object or marker - say, a lamppost at the side of the road - it should be two seconds before you pass that same object. You need to slow down and keep your distance if it's less than that.
What is braking distance?
Without functioning brakes, even if you keep a safe stopping distance, there's no guarantee you'll be able to avoid a collision if something unexpected happens on the road.
Your braking distance is the distance it takes for your car to come to a complete stop from when the brakes are first applied. The official distances supplied by The Highway Code are in the table below.
| Speed | Braking distance |
|---|---|
| 20mph | 6 metres |
| 30mph | 14 metres |
| 40mph | 24 metres |
| 50mph | 38 metres |
| 60mph | 55 metres |
| 70mph | 75 metres |
What is thinking distance?
Thinking distance is the time it takes to react and apply the brakes after you perceive a need to stop.
| Speed | Thinking distance |
|---|---|
| 20mph | 6 metres |
| 30mph | 9 metres |
| 40mph | 12 metres |
| 50mph | 15 metres |
| 60mph | 18 metres |
| 70mph | 21 metres |
How do I work out stopping distances?
Stopping distance is a driving theory test favourite that many of us quickly forget when taking to the roads for real. However, the stopping distance formula is handy for quick calculations, ensuring road safety.
The formula asks you to multiply your speed by intervals of 0.5, starting with two at 20mph, which will give you your stopping distance in feet.
20mph x 2 = 40 feet
30mph x 2.5 = 75 feet
40mph x 3 = 120 feet
50mph x 3.5 = 175 feet
60mph x 4 = 240 feet
70mph x 4.5 = 315 feet
If you work in metrics, divide the distance (in feet) listed above by 3.3 to get the stopping distances in metres. The slower the car is travelling, the shorter the overall stopping distance.
Below are the average stopping distances for a typical family car.
| Speed | Stopping distance |
|---|---|
| 20mph | 12m (40 feet) |
| 30mph | 23m (75 feet) |
| 40mph | 36m (118 feet) |
| 50mph | 53m (174 feet) |
| 60mph | 73m (240 feet) |
| 70mph | 96m (315 feet) |
Factors that can affect stopping distances
Weather
The stopping distance of cars is longer in adverse weather conditions. Slippery roads increase the braking distance, and poor visibility can increase the driver's thinking distance.
Here are some guides you might find helpful:
Driver
Consumption of drugs and alcohol whilst driving is illegal and hugely affects reaction time. Other dangerous distractions include using a mobile phone (which is also against the law), loud music, and disruptive passengers. Tiredness is another major factor.
Car condition
Tyre condition has a significant impact on your car's ability to stop. For this reason, it's crucial to avoid driving on under-inflated or bald tyres. Similarly, the effectiveness of the brake system has a role in how quickly your car can stop.
Find out how long tyres last & how to make them last longer.
Road condition
Road condition is, unfortunately, something you can't control. But you should still be prepared for every eventuality. Black ice, oil spills and surface water make it harder to slow down.
How do you check your brakes are working?
As you set off in your car, push the brake pedal. It should have decent resistance without feeling spongy or too hard to press, and your car shouldn't pull to one side. If the brakes feel slow to react or display any of the symptoms mentioned here, get them checked by a mechanic; they may need replacing.
Here are five brake problems you shouldn't ignore.
Worried about your car's brakes? It's better to be safe than sorry. Find a local garage to check them on the UK's most trusted garage network.
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Written by Ellie
Ellie is WhoCanFixMyCar’s Content Writer. She has a BA in English literature from Durham University, a master’s degree in creative writing, and three years of experience writing in the automotive industry. She currently drives a Suzuki Swift.