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Braking distance and reaction distance
How far does the car travel before it stops? The answer depends on three parts: reaction distance, braking distance and stopping distance — and all three are strongly affected by speed and road conditions. Understanding the difference helps you judge safe distances and avoid driving into what is in front of you.
Rules & Regulations
- The stopping distance consists of reaction distance plus braking distance; both must be taken into account when you judge a safe following distance.
- As a driver you should adapt your speed to road, weather and visibility conditions so that you can stop in time for unexpected obstacles.
- Poor road conditions (rain, snow, ice, leaves, oil) increase the braking distance and require you to keep a greater distance and lower speed.
- The vehicle's technical condition—tires, brakes and load—affects the braking distance and should be maintained to operate safely.
- When visibility is limited or when you approach areas with a risk of cross traffic (pedestrians, cyclists, intersections), you should reduce speed and allow for a longer stopping distance.
Tips for Drivers
- Scan the road well ahead so you have time to react before you need to brake — this effectively reduces the reaction distance by allowing you to spot hazards earlier.
- Increase the distance to the vehicle in front of you in rain, snow or icy conditions; braking distance becomes significantly longer on wet or slippery surfaces.
- Check tire tread depth and air pressure regularly — poor tire grip significantly increases braking distance.
- Brake gently and in good time instead of having to brake hard at the last moment; this gives better control and reduces the risk of skidding or collision.
Common Mistakes
- Confusing reaction distance with braking distance or believing that stopping distance is just the braking distance.
- Underestimating the effect of increased speed on braking distance and therefore keeping too small a gap.
- Believing that ABS always gives a shorter braking distance on all surfaces—ABS helps you steer during heavy braking but does not always reduce braking distance equally on every surface.
Exam Tip
Theory questions may ask you to distinguish between reaction distance and braking distance or to add them together to get stopping distance. Be careful to read the question: sometimes numbers are given that require calculation, other times the test assesses understanding of how road conditions affect both components.
Did You Know?
Braking distance increases roughly with the square of the speed: if the speed doubles, the braking distance theoretically becomes about four times greater, assuming braking force remains the same.
Frequently Asked Questions
What is meant by reaction distance?
Reaction distance is the distance the vehicle travels during the time it takes for the driver to perceive the need to brake and to begin braking. It is affected by attention, fatigue, and how much the driver anticipates hazards.
What affects the braking distance most?
Braking distance is affected by current speed, road conditions, the condition of the tires, vehicle weight, and brake efficiency. Poor grip or a heavier vehicle gives a longer braking distance.
How should I adjust the following distance in rain or snow?
Increase the distance markedly compared with dry conditions so you have margin for longer braking distance and possible skids. Adjust your speed so that the stopping distance is within your line of sight.
Does ABS make the car always stop faster?
ABS prevents the wheels from locking and helps you retain steering control during heavy braking. That does not automatically mean the braking distance will always be shorter on all surfaces; on some very slippery surfaces the difference can be small.
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