Driving Reaction Time Test
You are following a car. When its brake lights come on, click, tap or press Space, then see how far you would travel before you even start to brake.
- Brake light stimulus
- Thinking distance at your speed
- mph or km/h
- Highway Code comparison
Your times against the average
Dots are your attempts, the solid line is your median and the curve shows the usual spread of online scores.
Your history on this device
Finished rounds appear here with your personal best. They are stored only in this browser and never sent anywhere.
Your stopping distances
Finish a round to fill in your columns. Highway Code thinking distances assume about 0.67 s. Braking distances are typical dry road figures.
| Speed | Your thinking distance | Highway Code thinking | Braking | Your stopping distance |
|---|---|---|---|---|
| 20 mph | - | 6.0 m | 6.2 m | - |
| 30 mph | - | 9.1 m | 13.9 m | - |
| 40 mph | - | 12.1 m | 24.7 m | - |
| 50 mph | - | 15.1 m | 38.6 m | - |
| 60 mph | - | 18.1 m | 55.6 m | - |
| 70 mph | - | 21.1 m | 75.7 m | - |
What is a driving reaction time test?
It measures how quickly you respond to the car in front braking, then turns that time into distance. Every 0.1 seconds at 70 mph is 3.1 metres (10 feet) travelled before you start to slow down. Here a car sits ahead of you on the road. After a random wait its brake lights come on, and you press as fast as you can. The test reports your reaction in milliseconds, converts it to thinking distance at the speed you choose and adds a typical braking distance to give a full stopping distance. Your result sits next to the UK Highway Code figures, which assume about 0.67 seconds to react.
How to test your driving reaction time
- Choose your units and speed.
- Click or tap the road, or press Space, to start following the car.
- Watch the car. After a random wait of 2 to 7 seconds its brake lights come on.
- Press the instant you see them. You get your reaction time and the distance covered before you reacted.
- After five stops, compare your median thinking and stopping distances with the Highway Code figures.
Why use this driving reaction test
- Reaction time as distanceSee your result in metres and feet at your chosen speed, which is what reaction time means on the road.
- Any common speedSwitch between 20 and 70 mph or 30 and 120 km/h and the distances update instantly.
- A road-like signalYou react to small brake lights on the car ahead, not to a whole screen changing colour.
- Your history stays on this deviceEvery session is saved in this browser with your personal best. No account, nothing sent to a server, and one button clears it.
Who uses the driving reaction test
- Learner drivers. Make stopping distances stick before the theory test by seeing your own numbers.
- Driving instructors. Show a pupil how much a half-second glance at a phone really costs.
- Road safety lessons. A quick classroom demo of speed, reaction time and stopping distance.
- Before a long drive. A result far slower than your usual one is a good reason to rest first.
Highway Code stopping distances
The UK Highway Code gives these typical stopping distances for a car in good condition on a dry road. Thinking distance is how far you travel while reacting; braking distance is how far the car takes to stop once the brakes are on.
| Speed | Thinking distance | Braking distance | Stopping distance | In feet |
|---|---|---|---|---|
| 20 mph | 6 m | 6 m | 12 m | 40 ft |
| 30 mph | 9 m | 14 m | 23 m | 75 ft |
| 40 mph | 12 m | 24 m | 36 m | 118 ft |
| 50 mph | 15 m | 38 m | 53 m | 175 ft |
| 60 mph | 18 m | 55 m | 73 m | 240 ft |
| 70 mph | 21 m | 75 m | 96 m | 315 ft |
Why real braking takes longer than this test
On screen you know a signal is coming and only a finger moves. On the road you first have to notice the hazard, often in the corner of your eye, decide it is real, lift your foot and press the pedal. Studies of drivers find that the whole sequence takes about 0.7 seconds when a driver is expecting to brake and around 1.5 seconds for a genuine surprise. Doubling your speed doubles the thinking distance but roughly quadruples the braking distance, which is why a small speed change makes such a difference to the total.
What your score includes
Your result is the time from the frame that shows the change on your screen to the moment your device registers the press. The test makes the change inside requestAnimationFrame and starts the clock at the timestamp of the next frame, which is when the changed frame is handed to the display. The stop time is the timestamp your device stamped on the click, tap or key press, so page scripts, ads and rendering do not add to your time. That is also why scores here can be about one frame lower than on tests that start the clock when the change is requested.
| Part of the chain | Typical delay | How to reduce it |
|---|---|---|
| Screen refresh | Up to one frame: 16.7 ms at 60 Hz, 6.9 ms at 144 Hz, 4.2 ms at 240 Hz | Use a high refresh rate display |
| Monitor or TV processing | A few ms on most monitors, often much more on TVs outside game mode | Turn on game mode or low latency mode |
| Mouse | 1 ms at 1000 Hz polling, up to 8 ms at 125 Hz | A wired or gaming wireless mouse |
| Touchscreen | Often tens of milliseconds | Compare scores on the same device |
| Keyboard | A few ms on gaming keyboards, more on some laptop keyboards | Use the same input every time |
| Browser and page | Removed by the timestamps described above | Nothing to do |
Example: what 0.31 seconds means at 30 mph
A median of 0.31 seconds at 30 mph means 4.2 metres (14 feet) travelled before you react. Add the typical 14 metre braking distance and you need about 18 metres to stop. The Highway Code allows 9 metres of thinking distance at 30 mph, because a real driver also has to move a foot to the pedal and is not always looking straight at the car ahead.
What to expect from the result
This measures a finger press on a screen, not a foot on a pedal. Moving your foot from the accelerator to the brake adds roughly 0.2 to 0.3 seconds, and surprise adds much more: driver studies put full brake reaction at about 0.7 seconds when the driver expects to brake and up to about 1.5 seconds when surprised. Braking distances follow the Highway Code typical figures for a dry road and a car in good condition; on wet roads they can double. Never use your phone or this test while driving.
Driving reaction time FAQ
What is the average driver reaction time?
For an expected event, studies put it at about 0.7 seconds from seeing a hazard to pressing the brake, and about 1.5 seconds for a complete surprise. The UK Highway Code thinking distances assume about 0.67 seconds. On this screen test most people score 0.25 to 0.35 seconds, because only a finger moves and you know the brake lights are coming.
How is thinking distance calculated?
Thinking distance is speed multiplied by reaction time. Convert the speed to metres per second (mph × 0.447, or km/h ÷ 3.6) and multiply by your reaction time in seconds. At 50 mph, which is 22.4 m/s, a 0.7 second reaction means 15.6 metres travelled before braking starts.
What are the Highway Code stopping distances?
Typical stopping distances are 12 m at 20 mph, 23 m at 30 mph, 36 m at 40 mph, 53 m at 50 mph, 73 m at 60 mph and 96 m at 70 mph. Each is thinking distance plus braking distance on a dry road.
What slows a driver's reactions?
Phones and other distractions, tiredness, alcohol and drugs, some medicines, and age. Hands-free calls slow reactions too, because attention matters more than where your hands are.
Is this an official driving or medical test?
No. It is a quick self-check and a teaching aid. Real braking involves your foot, the pedal and the car, and real hazards are not announced. Use it to see how distance grows with speed and reaction time.
Are my results saved or sent anywhere?
Your results are saved only in this browser, so you can see your history and personal best next time. Nothing is sent to a server, there is no account, and you can clear the history at any time.
More reaction and input tests
Try the reaction time test, F1 reaction test, audio reaction time test or ruler drop test. To check the hardware behind your score, run the refresh rate test, mouse test or keyboard test, or see how fast you can click with the CPS test. All of them are in the device tests collection.