Road safety

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How far does it take a car to stop?

Change the speed, reaction time, road conditions and tyre condition and see straight away how the stopping distance changes. Put two scenarios side by side and see how fast one car is still going where the other has already stopped.

Ready-made comparisons:
Speed and driver
Road
Water on the road
Tyres Wet grip class (EU tyre label)
Tyre condition
Car

Loading the calculation model…

Things to try

  • Speed. Choose “50 vs 70 km/h”. The obstacle is placed where the 50 km/h car stops — see how fast the 70 km/h car is going when it gets there.
  • Attention. During the reaction time the car keeps going at full speed. At 50 km/h every extra second is about 14 metres.
  • Tyres and weather. Tread depth matters especially on wet roads; summer tyres on snow and melting ice around zero are the most dangerous situations.
  • Presenting. “Presentation mode” opens the calculator full screen. “Copy link” saves all your choices in the address — you can send the scenario to someone or prepare it for a presentation.

What the calculation takes into account

Braking is calculated in small time steps: tyre and road grip at the given speed and temperature, ABS, brake performance, load, air resistance and road gradient. The model is calibrated against 369 measured braking distances from independent tyre tests and checked against about 1300 further magazine test results.

The result is an estimate, not a measurement. Each result shows a likely range. The real braking distance also depends on the specific tyre, the road surface and the driver. Ice means ordinary road ice; on smooth glare ice the braking distance is longer (choose “Smooth ice”).

Sources

  • ADAC, Tekniikan Maailma, UTAC, Vi Bilägare, Auto Bild, Za Rulem and others — independent tyre tests
  • EU product register EPREL and the tyre label test method UNECE R117
  • DEKRA — the effect of tread depth on wet roads
  • Green, M. (2000). “How long does it take to stop?” Transportation Human Factors 2(3) — reaction time: prepared driver approx. 0.7 s, unexpected hazard approx. 1.25–1.5 s
  • VTI (Sweden), Statens vegvesen (Norway), Estonian Road Administration — friction coefficient on road ice

The tool is free for everyone — drivers, parents, schools and driving schools. The page has no ads, prices or shops.