Brake Reaction Test

You are following the car ahead at your chosen speed and gap. When its red brake lights come on, brake as fast as you can, but ignore the amber indicators.

Educational tool only. This is a demonstration of reaction time and stopping distance. It is not a driving assessment, a medical or cognitive test, or a measure of anyone's fitness to drive.

TAP TO STARTspace or enter works too

RUN– LAST– MEDIAN– BEST– FALSE0 CRASHED0

R1–

R2–

R3–

R4–

R5–

Complete five brake reactions for your rating.

What your reaction means on the road

Distance travelled before your foot even reaches the brake, at your median of –:

–used reacting

–your gap

–to spare when you braked

That is reaction distance only: your tyres still have to stop the car after it. Add your braking distance in the simulator.

Show the working: every number on this page

What this tool is, and what it cannot tell you

This is an educational demonstration, not a driving assessment. It is not a medical or cognitive test, it is not a measure of fitness to drive, and nothing here should be used to judge whether anyone is safe on the road.

Your reaction here is a best case. You know a brake light is coming and you are watching for it, so this measures a simple, expected reaction. Reacting to something genuinely unexpected on the road takes substantially longer, and published road-design guidance allows more again. Treat the number as the floor of what you are capable of, not as your reaction time in traffic.

The braking figures are best case too. They come from the same engine as our braking simulator, calibrated against published tyre tests on a dry sealed surface with good tyres in good condition. An ordinary car on an ordinary road needs more room than this. Rain is modelled only as a depth of water on sealed asphalt, and nothing else varies: no gradient, no load, no worn tyres, no vehicle differences.

Both cars are treated as identical and brake equally hard, which is what makes your gap in seconds line up exactly with the time you have. Real vehicles differ.

Your device is part of the measurement. Screen refresh and input handling add a few hundredths of a second, and a slow or busy device adds more.

The ratings compare you against this tool's own bands, chosen to spread results across a useful range. They are not a published standard.

Your results stay in your browser. Nothing you do here is recorded or sent to us, and no third-party service is contacted: the fonts are served by this page itself and the 3D library comes from our own content library.