Calculation of stopping distance

Stopping distance is the sum of reaction distance and braking distance. Both increase sharply with speed, and in the class B theory test, you are often asked questions about exactly this.

The formulas you need to know

The reaction distance assumes one second of reaction time. If you are tired or inattentive, the time and thus the distance increase.

How stopping distance increases with speed

Note that the braking distance quadruples when the speed doubles. Therefore, speed control is crucial for safety.

Factors that increase stopping distance

• Wet or slippery conditions double the braking distance. On ice, it can become ten times longer. Read more about driving in bad weather and road conditions .
• Worn tires reduce grip, especially in hydroplaning .
• Poor reaction time from fatigue, distractions, or mobile use adds many meters to the reaction distance.
• Downhill gives gravity an extra effect that extends braking distance.

Rule of thumb for distance

Use the three-second rule to maintain a safe distance to the car in front. Three seconds give you enough margin to react and brake under normal conditions.

At higher speeds, such as on European roads and national highways , you should increase the distance further because braking distance increases exponentially.

Further reading

• Three-second rule
• Adjusted speed and hidden danger
• Speed limits and speed rules
• Braking distance and reaction time