What is braking distance and how to calculate it?

When sitting behind the wheel of a car, there are many factors that influence safety and can modify the response of the driver. Among these factors, one of the most sensitive is braking distance and response time, something that worries many drivers.

There are many reasons that can cause a driver to react and have to brake suddenly. From a pedestrian crossing between two cars, an animal crossing the road or a traffic light turning red. In this sense, when you step on the brake, the car does not stop instantly, but continues to move for an instant. To this movement, we must add the time it takes for the driver to react and step on the brake.

This reaction time is usually no more than two or three seconds . However, there are factors that can cause it to increase, so you should know what they are. The speed, the experience of the driver, the consumption of alcohol, medicines and drugs or simple fatigue. 

On the other hand, braking time can also be affected for various reasons. What can increase the stopping distance? The answer is: many things. From worn brake pads, to the speed of the car, the condition of the road and the vehicle, or the skill of the driver. 

By adding these two factors, you will realize that braking can change a lot depending on the circumstances . In this sense, a meter more or less, can mean the difference between avoiding an accident or suffering one. For this reason, it is important to know what braking distance and reaction are, as well as the different factors that can influence it.

What is braking distance?

This is the distance that the vehicle travels from when the brake is applied until it comes to a complete stop. These meters do not depend exclusively on the driver, since there are many factors that can cause them to increase. For example, the state of the car and the road. Since if it has rained, the braking distance will be greater.

Fortunately, there are certain things that can be done to reduce this distance. First of all, it is important to keep the brakes and tires in good condition, carrying out regular checks and maintaining the correct tire pressure at all times.

What factors can increase reaction and braking distance?

The distance necessary to stop safely depends on factors such as: environmental conditions, the load carried by the car, the condition of the suspension, brakes and tires, as well as the speed and condition of the road. 

First of all, the condition of the brakes must be controlled, since as they wear out, the braking space is greater. In this sense, the brake pads should be checked annually and, if possible, changed every 15,000 km, since with use they harden and lose their power. 

On the other hand, the tires also influence this factor, so they must be kept in optimal conditions. Tires in poor condition can triple your braking distance . Similarly, incorrect inflation or low pressure will also increase it. On the other hand, it is not possible to drive on Spanish roads when the tire tread is less than 1.6 mm, since the less tread it has, the greater the risk of an accident.

Environmental factors also affect stopping distance. For example, when it rains it is three times higher and when it snows it can increase up to five times. It is worth mentioning that the reaction distance is 63 meters on snowy pavement with normal tires. Therefore, if you ask yourself, in this situation, what is the safety distance between vehicles? The answer is more than 150 meters between the two cars.

What is the safety distance between cars?

The DGT does not offer a clear answer on the distance in meters. Instead, the traffic regulation in Spain states that the minimum safety distance is three seconds . However, this can be a bit tricky as it will vary based on a number of factors.

For example, does speed influence reaction distance? The answer is yes. It is for this reason that the so-called “square rule” is used to calculate the safety distance. This calculation is done by removing the last digit of the speed and multiplying the number by itself. For example, if driving at 80 km/h, we eliminate the 0, leaving the 8, which is multiplied by itself. Therefore: 8×8=64. 

With this rule you can get the answer to questions like: “On a road, which vehicles must keep a minimum separation of 50 meters?”. Which, in this case, would be all those who drive at 50 km/h. On the other hand, when driving in the city, with a speed limited to 30 km/h, the safety separation will be 9 meters.

Can you increase the driver’s reaction time?

As already seen, the answer is yes. Therefore, when these times are greater, either due to the state of the road or the conditions of the driver himself, the safety distance will also have to be greater. 

Specifically, the DGT advises that in this type of situation the security separation should be double that recommended . That is, if we drive at 80 km/h in the rain, the distance with the car in front should be 128 meters.

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