Driving theory
Stopping distance – reaction distance and braking distance
Quick answer
Stopping distance is how far the car travels from the moment you notice a hazard until it stands still. It is reaction distance plus braking distance. Swedish lessons often use a dry-asphalt rule of thumb: reaction ≈ (km/h ÷ 10) × 3 metres and braking ≈ (km/h ÷ 10)². That is a teaching approximation, not a legal figure.
Key facts
- Stopping distance = reaction distance + braking distance.
- Reaction distance depends on speed and your reaction time (fatigue, alcohol, phones and darkness increase it).
- Braking distance depends on speed, tyres, brakes, road surface and slope. Double the speed and braking distance is about four times as long.
- The rule of thumb assumes roughly dry asphalt and about one second of reaction. Wet, ice and gravel need more room.
How the teaching rule works
First take speed in tens: 50 km/h → 5, 70 → 7, 90 → 9.
Reaction distance: that number × 3. At 50 km/h that is 15 metres — roughly how far you roll while you notice and start braking.
Braking distance: that number squared. At 50 km/h the rule gives 25 metres on dry asphalt.
Stopping distance: 15 + 25 = 40 metres at 50 km/h. At 90 km/h: 27 + 81 = 108 metres. Speed grows faster than most people expect.
On ice, snow or wet roads braking distance can be several times longer. The rule teaches magnitude. It does not replace the gap you need in the weather you are driving in.
Worked examples (dry asphalt, teaching rule)
- 50 km/h
- Reaction 15 m, braking 25 m, stopping 40 m. Longer than most people picture in a 50 zone.
- 70 km/h
- Reaction 21 m, braking 49 m, stopping 70 m.
- 90 km/h
- Reaction 27 m, braking 81 m, stopping 108 m. Almost three times the 50 km/h stopping distance, even though speed is not doubled.
Common mistakes
- Mixing up braking distance and stopping distance — stopping distance also includes the time before your foot hits the pedal.
- Using the dry-asphalt rule on ice.
- Thinking ABS dramatically shortens braking distance. ABS helps you steer while braking; grip still sets the limit.
What to remember
Stopping distance = reaction + braking. Speed hits braking distance hardest. The rule of thumb is a dry-asphalt teaching tool. Leave a gap that fits the real stopping distance in front of you.
Frequently asked questions
- How do you calculate stopping distance?
- Add reaction distance and braking distance. Teaching rule on dry asphalt: (speed/10)×3 plus (speed/10)². At 50 km/h: 15 + 25 = 40 metres.
- What is the difference between braking distance and reaction distance?
- Reaction distance is how far you roll from seeing the hazard until braking starts. Braking distance is how far you roll while braking. Together they are stopping distance.
- Does the rule of thumb appear on the theory test?
- The test can ask about the concepts and how speed and road conditions change the distances. The numbers are a teaching aid. Read the question and do not mix up the terms.
Sources
Knowledge-test facts come from Trafikverket and Transportstyrelsen. Always check the authority page if a rule may have changed.
Reviewed 2026-09-10 · körkortsvägen.se is not Trafikverket or Transportstyrelsen and does not reproduce official exam questions.