Calculation
s = v² / (2·a)
Braking distance grows with the square of speed; doubling speed quadruples braking distance at the same deceleration.
Dubbel Mechanik B 2.1.1 Kinematik, gleichmäßig beschleunigte Bewegung: s = v²/(2·at)
Vehicle braking distance
Braking distance grows with the square of speed; doubling speed quadruples braking distance at the same deceleration.
MINTSI
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Result
Select a target and calculate.
Understand the inputs
- Braking distance s — Distance travelled from brake application to standstill.
- Initial speed v — Speed at the moment braking begins.
- Braking deceleration a — Average deceleration during braking; passenger cars on dry roads achieve about 7 to 9 m/s².
Example
v=100 km/h (27.78 m/s) and a=7 m/s² give s=27.78²/(2·7)≈55.1 m.
Assumptions and limits
Constant deceleration throughout braking and a level, dry road; reaction time, ABS control effects and road condition (wet, snow) are excluded.
Understand Vehicle braking distance
This calculator determines the pure braking distance of a vehicle from initial speed and braking deceleration, excluding driver reaction time.
What does this quantity describe?
From uniformly decelerated motion, braking distance follows as s=v²/(2a), where v is speed at brake application and a the average deceleration.
Formula and variables
s = v² / (2·a)
s = v²/(2·a)
| Symbol / input | Meaning |
|---|---|
| Braking distance s | Distance travelled from brake application to standstill. |
| Initial speed v | Speed at the moment braking begins. |
| Braking deceleration a | Average deceleration during braking; passenger cars on dry roads achieve about 7 to 9 m/s². |
Choose the inputs correctly
v is the speed at the moment braking begins, a the average deceleration achieved during braking.
How to use the calculator
Take v from a speedometer reading or driving scenario, and a from vehicle data or typical experience values for the road surface.
Worked example
v=100 km/h (27.78 m/s) and a=7 m/s² give s=27.78²/(2·7)≈55.1 m.
Understand the result and units
Since braking distance grows with the square of speed, a 41% higher speed already doubles braking distance.
v is a speed, a an acceleration. s is output as a length.
Typical applications
Traffic-safety considerations, driving-school instruction and accident reconstruction as a building block alongside stopping distance.
Assumptions, limits and common mistakes
Constant deceleration throughout braking, a level and dry road; reaction time, ABS control behaviour, road condition and vehicle load are excluded.
Common mistake: Do not confuse braking distance with stopping distance; the latter additionally includes the distance travelled during reaction time.
Frequently asked questions
What is “Vehicle braking distance” used for?
Traffic-safety considerations, driving-school instruction and accident reconstruction as a building block alongside stopping distance.
Where do the input values come from?
v is the speed at the moment braking begins, a the average deceleration achieved during braking.
What does the result not cover?
Constant deceleration throughout braking, a level and dry road; reaction time, ABS control behaviour, road condition and vehicle load are excluded.