Choose the drive
Set speed, following gap, surface, time of day, distraction and camera. The selected values are held while a run is active.
Free driving tool
Brake Reaction Test
Follow the car through a generated 3D drive. Brake for real red brake lights, ignore the amber indicators, and see how far you travelled before braking began.
Free to useNo account needed
Know what this test is measuringSee how to run five rounds, choose the camera and conditions, read the median, and understand the limits of a screen reaction test.
Live reaction testFive lights. One median.Red means brake. Amber means wait.
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.
Tyres as new · 8 mm
Pressure correct
Tyre age 0 years
Wet grip grade C
1500 kg, unladen
ABS, brakes cold
Sealed asphalt
Flat, no camber
20 °C
Car ahead identical
Straight line only
It always stops fully
No other traffic
TAP TO STARTspace or enter works too
RUN–
LAST–
MEDIAN–
BEST–
FALSE0
CRASHED0
R1–
R2–
R3–
R4–
R5–
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.
Powered by 
Help, method and limits
Brake Reaction Test guide
Run the test correctly, understand what each setting changes, and keep a screen score in its proper context.
React only to red
Start the run, then brake when the car ahead shows real red brake lights. Amber indicators are deliberate false cues. Use the brake control, tap, Space or Enter.
Conditions and camera
Compare dry, wet and heavy-rain drives in daylight or at night. Switch between chase and driver’s-seat views without changing the underlying timing.
Distraction option
The phone option temporarily removes the road from view. Its timing controls demonstrate how even short glances consume the following gap.
Median of five
The central result is the median of the five correct reactions. One unusually quick or slow round therefore has less influence than it would in an average.
Distance before braking
The result converts time into distance at the selected speed. That is reaction distance only; the vehicle still needs braking distance afterward.
Show every number
The built-in working section keeps the timing, distance conversion and braking assumptions inspectable rather than hiding them behind a score.
What the score cannot prove
This is an educational screen test. It is expected, visually simple and affected by the device. It is not a driving, medical or cognitive assessment.
Ready to continue the test? Your settings and completed rounds have been kept.