The faster a car goes, the more time and distance it needs to come to a stop. If a car speeds up just a little bit, the stopping distance needed becomes much longer.
Leaving enough distance in front will:
- Give you a better view of the road ahead
- Let you react and stop in time if cars in front suddenly brake
- Help with fuel economy – you’ll drive more smoothly and won’t be braking every time the car in front slows down
When preparing for your theory test, you should be aware that there are several types of distances, each one with a different name and meaning. These are:
- Thinking distance
- Reaction distance
- Braking distance
- Overall stopping distance
What is stopping distances?
Stopping distance is the distance a vehicle travels after the driver hits the brakes until the vehicle comes to a complete stop. It includes both the time it takes the driver to recognise and react to a potential hazard (thinking distance) and the distance it takes for the vehicle to come to a stop once the brakes are applied (braking distance).
The stopping distance will increase the faster you drive and the wetter the road is. It also takes time to process what’s happening before you start braking.
The Highway Code shows this by splitting the typical stopping distance up into thinking distance and braking distance. You’ll need to remember the distances for your theory test.
The distances are based on the average car length in the UK and assume the road is dry.
Stopping distance formula
The formula for stopping distance is:
Stopping distance = thinking distance + braking distance
It is used to calculate the total distance a vehicle will travel before coming to a complete stop in response to a potential hazard.
It’s important to note that the stopping distance can vary depending on a number of factors, including the driver’s reaction time, the speed of the vehicle, the condition of the brakes, and the road surface. Drivers should always maintain a safe following distance from the vehicle in front of them and adjust their speed to the conditions of the road.
|Speed||Thinking + braking distance||Stopping distance|
|20mph||6m + 6m||12m (40 feet)|
|30mph||9m + 14m||23m (75 feet)|
|40mph||12m + 24m||36m (118 feet)|
|50mph||15m + 38m||53m (174 feet)|
|60mph||18m + 55m||73m (240 feet)|
|70mph||21m + 75m||96m (315 feet)|
The stopping distance at 20mph is around 3 car lengths. At 50mph it’s around 13 car lengths. If you’re travelling at 70mph, the stopping distance will be more like 24 car lengths.
What can affect stopping distance?
Stopping distances can be affected by a range of factors, including:
- Speed: The faster the vehicle is travelling, the longer it will take to stop.
- Vehicle condition: Worn brakes, poor tire condition, and faulty suspension can all increase the stopping distance.
- Road condition: Wet or icy roads reduce the grip of the tires on the road, increasing the stopping distance.
- Brake reaction time: The time it takes for the driver to recognize the need to brake and then physically apply the brakes.
- Driver reaction time: The time it takes for the driver to recognize a potential hazard and react to it.
- Load and weight of the vehicle: Heavier vehicles require longer stopping distances due to increased momentum.
- Poor weather conditions: Rain, snow, fog, and ice can all impact visibility and reduce the grip of the tires on the road, increasing the stopping distance. In wet conditions, braking distances can be doubled, and ice and snow can be multiplied by ten. This means, in icy conditions, it could take you further than the length of seven football pitches to come to a stop from 70 miles per hour.
Poor weather conditions can impact stopping distances in several ways. Wet roads increase the risk of aquaplaning, where the tires lose contact with the road surface, making it difficult to stop or steer. Snow and ice reduce the grip of the tires on the road, making it harder to slow down or stop, even with anti-lock brakes. Fog reduces visibility, making it harder to see hazards and react quickly, increasing the reaction time and the overall stopping distance.
What are thinking distances?
Thinking distance is the distance a vehicle travels while the driver reacts to a situation and decides to stop the vehicle. This means the distance a car moves during the time it takes for the driver to notice something is wrong, and then to hit the brakes.
The time it takes to react depends on many factors, including how alert the driver is, how much sleep they’ve had, and whether they’re under the influence of drugs or alcohol.
The faster the vehicle is going, the longer the thinking distance will be, so it’s important to be aware of potential hazards on the road to allow enough time to react.
The thinking distance (in feet) is the same as the speed (in mph).
Question: What is the thinking distance at 50mph?
Answer: Thinking distance at 50mph is 50 feet.
Speed & thinking before reacting distance
- 20mph – 6 metres
- 30mph – 9 metres
- 40mph – 12 metres
- 50mph – 15 metres
- 60mph – 18 metres
- 70mph – 21 metres
What are the factors that influence thinking distances?
- Your state of mind: Your emotional and mental state can affect how quickly you can react to a hazard. For example, if you are feeling stressed, anxious, or tired, your thinking distance may increase.
- Your driving experience and skills: Experienced drivers who have good hazard perception skills and can anticipate potential hazards may have a shorter thinking distance than less experienced drivers.
- The distractions present in your car: Anything that takes your attention away from the road, such as a mobile phone, loud music, or a passenger, can increase your thinking distance.
- Any possible impairment: Physical or mental impairments such as illness, fatigue, or medication can slow your reaction times and increase your thinking distance.
Tip: ‘Thinking distance is approximately 1 foot (ft) for every mph you are travelling at.’
What is braking distance?
Braking distance is the distance that a vehicle travels from the moment the brakes are applied until the vehicle comes to a complete stop. It is an important measure of a vehicle’s ability to stop safely and quickly and is affected by a number of factors including the vehicle’s speed, the condition of the road surface, the condition of the brakes and tyres, and the weight of the vehicle.
The formula for calculating braking distance is:
Braking distance = (vehicle speed ÷ 2) x reaction time + (vehicle speed ÷ 2)² ÷ braking deceleration
The first part of the formula, (vehicle speed ÷ 2) x reaction time, calculates the thinking distance or the distance that the vehicle travels during the driver’s reaction time to recognize and respond to a hazard on the road. The second part of the formula, (vehicle speed ÷ 2)² ÷ braking deceleration, calculates the braking distance or the distance that the vehicle travels while the brakes are applied and the vehicle is coming to a stop.
The braking distance is directly proportional to the speed of the vehicle. As the vehicle speed increases, the braking distance also increases, which means that it will take the vehicle longer to come to a complete stop. It is important for drivers to maintain a safe distance from the vehicle in front of them and to drive at a speed that is appropriate for the road conditions to ensure that they can stop safely and avoid collisions.
What factors affect braking distance?
Braking distance refers to the distance that a car travels once the brakes are applied until it comes to a complete stop. Braking distance is influenced by several factors, including:
- Brakes: The condition of the car’s brakes will affect braking distance, so keep them in good working order. Worn or damaged brakes will increase the distance it takes to stop the car. Anti-lock braking systems (ABS) can help maintain control and steer while braking, but they may actually increase braking distance on snow or gravel roads.
- Tyres: Tyres play a significant role in braking distance. The amount of tread on the tyres affects the grip on the road. Tyres with worn treads will travel further before coming to a stop than new tyres. The wet grip rating of a tyre is also important, with tyres rated A having the best grip, and G the worst. Braking distance is also affected by tyre pressure, as both over- and under-inflation will increase the distance it takes to stop.
- Weather conditions: Weather conditions can have a significant impact on braking distance. Wet or icy roads will require a longer distance to stop. In wet conditions, it’s recommended to double the gap between your car and the car in front, while in icy conditions, the gap should be even bigger.
- Road conditions: The condition of the road surface can also affect braking distance. Muddy or damaged roads can increase the distance it takes to stop the car.
- Weight: The weight of a car also affects the braking distance. Heavier cars require a longer distance to come to a complete stop.
The braking distance is influenced by a variety of factors, including the condition of the car’s brakes and tyres, weather and road conditions, and the weight of the car. It’s important to maintain and check the car’s brakes and tyres to ensure they are in good condition and adjust your driving according to weather and road conditions to reduce the risk of accidents caused by extended braking distances.
Note – ‘The most important point to remember here is that doubling your speed more than doubles your braking distance. Even just a small increase in speed will cause a substantial increase in braking distance.’
What is the 2-second rule?
The 2-second rule is a driving technique used to help drivers maintain a safe following distance behind the vehicle in front of them. It suggests that you should maintain a distance from the car in front of you that would take at least 2 seconds to cover if the car in front suddenly stops or slows down. This rule helps to prevent accidents by allowing enough time for the driver to react in case of an emergency or sudden change in traffic conditions.
To use the 2-second rule, you can follow these simple steps:
- Pick a fixed object on the road, such as a sign or a tree, that is even with the car in front of you.
- As the car in front of you passes the fixed object, start counting “one thousand and one, one thousand and two”.
- If your car passes the fixed object before you finish counting, you are following too closely and need to increase your following distance.
- If you finish counting before your car passes the fixed object, you have maintained a safe following distance.
It is important to note that the 2-second rule is a minimum recommended following distance and should be adjusted depending on weather and road conditions. In adverse conditions such as rain, snow, or ice, you should increase your following distance to allow for longer stopping distances. Additionally, if you are driving a larger vehicle, such as a truck or bus, you should increase your following distance as these vehicles require more time and distance to come to a complete stop.
Stopping distances on wet or icy roads
The stopping distances when it is wet or icy are significantly longer than when it is dry with good conditions.
- On a wet road, the stopping distance is at least double that of a dry road. For example, a car travelling at 60 mph on a dry road would take approximately 240 feet to stop, whereas, on a wet road, it would take around double that at 480 feet to stop.
- On icy roads, the stopping distance is even longer, up to ten times that of a dry road. For example, a car travelling at 60 mph on a dry road would take approximately 240 feet to stop, but on an icy road, it could take 10 times longer to stop up to 2400 feet. It’s essential to adjust your driving style to the weather conditions to ensure you can stop safely in time.
The braking distance at 30mph is approximately 23 meters or 75 feet. This includes both the thinking distance and the braking distance.
A braking distance is the distance travelled by a vehicle from the moment the brakes are applied to when the vehicle comes to a complete stop. It is an important concept in driving as it helps drivers understand the minimum amount of space needed to stop their vehicle in an emergency situation.
The braking distance formula is stopping distance = thinking distance + braking distance. It is used to calculate the total distance required for a vehicle to come to a complete stop after the driver has applied the brakes.
The two-second rule can help you remember stopping distances while driving. The rule states that you should keep a distance of at least two seconds from the vehicle in front of you to allow enough time to react and stop safely.
In rain, the stopping distance can increase by up to double the distance compared to dry conditions. This means you should leave a larger gap between your vehicle and the one in front of you to ensure you have enough time to brake safely.
Thinking distance refers to the distance that a vehicle travels while a driver recognises and processes a hazard and decides to apply the brakes. It is the distance a car travels before the driver starts to brake.
The stopping distances in the highway code is:
- at 20 mph, the total stopping distance is 40 feet or 12 meters
- at 30 mph, the total stopping distance is 75 feet or 23 meters
- at 40 mph, the total stopping distance is 120 feet or 36 meters
- at 50 mph, the total stopping distance is 175 feet or 53 meters
- at 60 mph, the total stopping distance is 240 feet or 73 meters
The total stopping distance for a car travelling at 20 mph is approximately 12 metres or 40 feet. This includes both the thinking distance and the braking distance.
The typical stopping distance when travelling at 70 mph in good conditions is 96 metres, or 315 feet. This includes the thinking distance and braking distance.
The shortest stopping distance at 60 mph is approximately 73 meters or 240 feet. This includes the thinking distance and braking distance required to bring the vehicle to a complete stop.
The stopping distance at 40mph is approximately 36 metres, which includes both the thinking distance and the braking distance.
Stopping distances can increase up to ten times in icy conditions compared to dry conditions. This means it is important to drive with extra caution and leave a larger gap between you and the vehicle in front.