Calculation
s = v·tR + v²/(2·a)
Stopping distance adds the distance travelled unbraked during reaction time to the actual braking distance.
Dubbel Kraftfahrzeugtechnik Q 4.2 (Anhalteweg = Reaktionsweg + Bremsweg, tr 0,5–1,2 s) mit Dubbel Mechanik B 2.1.1
Vehicle stopping distance (reaction plus braking distance)
Stopping distance adds the distance travelled unbraked during reaction time to the actual braking distance.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Stopping distance s — Total distance from perceiving the hazard to standstill.
- Initial speed v — Speed at the moment the hazard is perceived.
- Reaction time tR — Time from perceiving the hazard until the brake takes effect; commonly assumed about 1 s.
- Braking deceleration a — Average deceleration during braking.
Example
v=100 km/h, tR=1 s and a=7 m/s² give a 27.78 m reaction distance plus 55.12 m braking distance, totalling s≈82.9 m.
Assumptions and limits
Constant speed during reaction time and constant deceleration during braking on a level, dry road; extra allowance for shock reaction, ABS effects and road condition are excluded.
Understand Vehicle stopping distance (reaction plus braking distance)
This calculator determines a vehicle's full stopping distance, from perceiving a hazard to standstill, as the sum of reaction distance and braking distance.
What does this quantity describe?
During reaction time tR the vehicle travels unbraked distance v·tR; only after that does deceleration begin. Total distance is s=v·tR+v²/(2a).
Formula and variables
s = v·tR + v²/(2·a)
s = v·tR + v²/(2·a)
| Symbol / input | Meaning |
|---|---|
| Stopping distance s | Total distance from perceiving the hazard to standstill. |
| Initial speed v | Speed at the moment the hazard is perceived. |
| Reaction time tR | Time from perceiving the hazard until the brake takes effect; commonly assumed about 1 s. |
| Braking deceleration a | Average deceleration during braking. |
Choose the inputs correctly
v is speed when the hazard is perceived, tR reaction time until the brake takes effect, a the average braking deceleration.
How to use the calculator
Take v from the driving scenario, tR with the common assumption of about 1 s (typical driver) or an application-specific value, a as for pure braking distance.
Worked example
v=100 km/h, tR=1 s and a=7 m/s² give a 27.78 m reaction distance plus a 55.12 m braking distance, totalling s≈82.9 m.
Understand the result and units
At high speeds, braking distance contributes quadratically while reaction distance contributes only linearly to the total; at low speeds, reaction distance dominates instead.
v is a speed, tR a time, a an acceleration. s is output as a length.
Typical applications
Traffic-safety training, sizing safe following distances, and accident analysis.
Assumptions, limits and common mistakes
Constant speed during reaction time and constant deceleration afterward, a level and dry road; individual reaction-time variation, ABS effects and road condition are excluded.
Common mistake: Do not confuse tR with pure visual reaction time; the common 1 s assumption already includes perceiving, deciding and acting.
Frequently asked questions
What is “Vehicle stopping distance (reaction plus braking distance)” used for?
Traffic-safety training, sizing safe following distances, and accident analysis.
Where do the input values come from?
v is speed when the hazard is perceived, tR reaction time until the brake takes effect, a the average braking deceleration.
What does the result not cover?
Constant speed during reaction time and constant deceleration afterward, a level and dry road; individual reaction-time variation, ABS effects and road condition are excluded.