Tool: Brake Reaction Test Updated: 4 September 2026 Free · no signup
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Brake Reaction Test

React to real brake lights, dodge the indicator traps, and see how many metres your reactions cost at speed.

How it works ↓
The tool

How fast do you really brake?

You are following the car ahead at a speed and a gap you choose. When its brake lights come on, react. Ignore the indicator traps, and see how many metres your reaction time costs at speed. Five rounds, scored on your median. Set the road wet, the sky bright, or put a phone in your hand.

The short answer

You are following a car at a speed and a following gap you choose. When its red brake lights come on, brake. When the amber indicators flash, don't. Five brake lights make a run, scored on your median, and your time converts into metres travelled before your foot even reaches the pedal. Miss the moment and the car ahead fills your windscreen until you hit it. You can set the road wet, the sky dark or bright, and put a phone in your hand, then watch what each one costs you.

  • Expect 0.6 to 1.0 seconds, not the 0.2 s of click-the-colour reflex sites: this test makes you recognise and decide, which is what braking actually demands. The bands in full.
  • New here? Start with how to use it, which walks through the four setting groups and what each one changes.
  • Reaction distance is only half the story: your tyres still have to stop the car after it. The braking simulator adds that half.
  • Educational tool only. It is a demonstration of reaction time and stopping distance, not a driving assessment and not a measure of fitness to drive. What it cannot tell you.
  • Privacy: the test runs in your browser. Only your personal best is kept, on your device.
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In this guide
In this guide 9 sections

How toHow to use it

The test opens in setup mode so you can choose the drive before anything moves. Nothing is timed until you start, and the settings lock for the duration of a run so every round is measured against the same drive.

  1. Set your speed and your gap Open Drive and pick the speed you want to test at and the following gap in seconds. Both cars travel at that speed. The gap is the honest bit: set the one you actually leave, not the one you know you should.
  2. Choose the road and the light Conditions sets the road wet or dry and the sky dark or bright. Daylight is harder than it sounds, because brake lights have far less to stand out against.
  3. Add a distraction, if you dare Distractions puts a phone in your hand on a timer you choose, or turns the cabin light on. Both are optional and both are instructive.
  4. Pick your view View switches between the driver's seat and a chase camera behind the car. Full screen is here too on devices that support it.
  5. Tap to start, then watch the car ahead Press the stage, or the space bar. When the red brake lights come on, brake as fast as you can. When the amber indicators flash, do nothing: that is the trap, and reacting to it counts as a false start.
  6. Read the result, not just the number After five reactions you get a median and, below it, the metres that median costs at your chosen speed. If you crash, the run pauses and tells you why before you continue.

The shots below are shrunk to fit. Click any of them to enlarge, then use the arrows to move through the set.

Brake reaction test settings: speed, following gap, road conditions, distractions and camera view
Setup. Four setting groups, and the red bar listing everything the model holds constant.
Driver's seat view at night, following the car ahead at 100 km/h before it brakes
Driver's seat. The default view, holding your chosen speed behind the car ahead.
The car ahead switches on its red brake lights at night, the moment the brake reaction test is timing
The moment. Red lights on. Everything after this is your reaction time.
Eyes off the road overlay, showing what a glance at a phone hides while driving
Checking your phone. The road is still there. You are not looking at it.
Brake reaction test results: median reaction time, five round times and the distance travelled before braking
Your run. Five reactions, the median, and what it cost in metres.
Brake reaction test settings: speed, following gap, road conditions, distractions and camera view
Setup. Four setting groups, and the red bar listing everything the model holds constant.
Driver's seat view at night, following the car ahead at 100 km/h before it brakes
Driver's seat. The default view, holding your chosen speed behind the car ahead.
The car ahead switches on its red brake lights at night, the moment the brake reaction test is timing
The moment. Red lights on. Everything after this is your reaction time.
Eyes off the road overlay, showing what a glance at a phone hides while driving
Checking your phone. The road is still there. You are not looking at it.
Brake reaction test results: median reaction time, five round times and the distance travelled before braking
Your run. Five reactions, the median, and what it cost in metres.
Keyboard and screen. The space bar and the enter key both work as the brake, so you are not fighting a touchpad. On a phone, use the Full screen button under View: the stage is small in a page, and a small stage makes the brake lights harder to see than they should be.

SettingsEvery setting explained

Four groups, and every option changes something real in the simulation rather than just the scenery.

Drive

Setting Options What it changes
Speed 20, 50, 70, 90, 100, 110 Both cars travel at this speed. It sets how much road a tenth of a second is worth, and the braking distance the physics engine returns.
Units km/h or mph Switches the speedometer and every distance between metres and feet. Note that it keeps the number rather than converting it, so 100 km/h becomes 100 mph: a genuinely faster drive, not the same one relabelled.
Following gap 1 to 10 seconds How far back you sit, in time. Because both cars brake identically, this is also exactly how long you have to react before you hit them.

Conditions

Setting Options What it changes
Road Dry, Wet, Heavy rain Wet is about 1 mm of water, roughly the depth used in official tyre wet-grip testing. Heavy rain is about 2.5 mm. Both reduce grip through the same engine our braking simulator uses, and both add spray, reflections and shorter visibility.
Light Night, Daylight Night is the default because it is the easier test: red lights against a dark road. In daylight the brake lights ahead have far less to stand out against, which is a real effect and a measurable one.

Distractions

Setting Options What it changes
Phone Eyes on road, or Checking phone Covers the road with a phone screen on a timer. You cannot see the brake lights while it is up.
Check every 3-6 s through to 30-60 s How often you glance down. It is a range, not a fixed interval, because the danger is precisely that it is a lottery.
For 1-2 s through to 6-12 s How long each glance lasts. Sooner or later one of them lands on top of a brake light.
Cabin light Off or On Available at night only. It lights the cabin, your eyes adjust to suit it, and everything beyond the windscreen loses contrast.

View

Setting Options What it changes
Camera Driver's seat, or Chase Driver's seat is the default and the honest one. Chase sits behind your car, which makes the closing distance easier to judge than it is in real life.
Full screen On supported devices Appears only where the browser allows it. Worth using on a phone.
Pause motion On or off Stops the scenery moving for anyone who finds motion uncomfortable. It turns itself on if your device asks for reduced motion. The test still works; only the scenery stops.
Settings lock while you run. Once a run starts you cannot change the drive underneath it, so all five reactions are measured against the same conditions. The list of what the model holds constant stays readable throughout.

ResultsWhat your results mean

Your rating comes from the median of five brake reactions: the middle result, so one lucky guess or one slow blink doesn't swing your score. Results of 0.6 to 1.0 seconds are realistic for an attentive driver.

Median Rating What the tool says
Under 0.50 s Exceptional Highly alert, anticipating hazards.
0.50 to 0.70 s Excellent Alert driver, good conditions.
0.70 to 0.90 s Good Normal attentive driving, typical for most.
0.90 to 1.20 s Average Slower than most people manage when they are watching for it.
Over 1.20 s Slow Well down on what this test usually shows.

These bands are the tool's own, chosen to spread results across a useful range. They are not a published standard, and a slow result here is a prompt to try again when you are fresh rather than a finding about you.

Why this reads higher than reflex websites. Click-when-the-colour-changes tests measure raw reflex, typically around 0.2 to 0.25 seconds. Driving is harder than that: you have to notice the lights, recognise them as brake lights rather than indicators, decide, and then move your foot. That is what this test measures, and it is why road-safety models assume well over a second for a real emergency.

The test also counts two things that are not reaction times. A false start is braking for the amber indicators, or before anything happened at all. A crash is reacting too late to stop in the gap you set. Neither is scored as a reaction, and both are worth more attention than the headline number.

ScienceHow driving reaction time works

Braking to a hazard is three steps, and each one costs time:

  • Recognition: your eyes register the brake lights and your brain works out what they are. Roughly 0.15 to 0.3 seconds.
  • Decision: brake, swerve, or nothing? Roughly 0.1 to 0.3 seconds. This is the step the yellow-indicator trap exercises.
  • Movement: foot off the accelerator and onto the brake. Roughly 0.15 to 0.25 seconds.

Those ranges describe an alert driver who is expecting the hazard, and they add up to about 0.4 seconds on a great day. Fatigue and distraction stretch every one of them, which is how a real braking reaction reaches well over 1.5 seconds. At 100 km/h your car covers 27.8 metres every second, so each tenth of a second is another 2.8 metres travelled before the brakes do anything at all.

There is a second reason your road reaction is longer than your result here: you knew the brake light was coming. A genuinely unexpected hazard takes substantially longer to process, and road-design guidance allows longer again for the drivers it plans around.

FactorsWhat slows your reactions down

  • Fatigue. The heavyweight. Research by Dawson and Reid (Nature, 1997) found that being awake 17 hours impairs performance about as much as a 0.05% blood alcohol level. If your results sit over a second, tiredness is the first suspect.
  • Phones. A conversation loads the same decision-making the test measures, and hands-free does not remove that load. Texting is in a category of its own. The New Zealand Road Code puts the cost plainly: at 90 km/h, two seconds with your eyes off the road is 50 metres travelled. Turn on the phone setting and the test bills you for exactly this.
  • Alcohol and drugs. Slower recognition and slower decisions, well before you feel "drunk".
  • Medication. Antihistamines, sleep aids and some pain medication carry drowsiness warnings for exactly this reason.
  • Time of day. Reactions dip in the small hours and mid-afternoon, when your body clock runs low.
  • Age. Reaction time lengthens gradually with age, though experience and hazard anticipation claw a lot of it back.
  • Light and contrast. Brake lights are easy against a dark road and much harder in bright daylight, and an interior light kills your contrast further. Both are settings here, so you can measure the difference on yourself instead of taking our word for it.

Conditions change day to day, so one run is a snapshot rather than a verdict. Test yourself tired and test yourself fresh, and the gap between the two numbers will tell you more than either one on its own.

GapWhat following gap should you set?

Set the gap you actually leave. That is the number worth testing, and the test is built so that the gap in seconds is exactly the time you have: because both cars brake identically, a 2 second gap gives you 2 seconds to react, at any speed. That is the two-second rule, demonstrated rather than asserted.

New Zealand's Road Code teaches a 2-second rule for normal conditions and a 4-second rule when the road is wet or slippery, in bad weather, or when towing. You count it off a landmark as the car ahead passes it. It is deliberately stated in seconds rather than metres, because seconds scale with speed and car lengths do not.

The law is a floor, not a target. The Land Transport (Road User) Rule 2004 sets minimum following distances in metres: 36 metres where you are doing 90 km/h or more. At 100 km/h that is about 1.3 seconds. The Road Code's 2 seconds is roughly 56 metres at the same speed, so the rule you were taught is considerably more generous than the minimum you can be measured against. Set the test to 1 second and you will see why the extra matters.

Following distance is a subject of its own. Our following distance guide covers every situation, including towing, heavy vehicles and being tailgated yourself.

TyresReaction distance plus braking distance

Your total stopping distance is two pieces: the metres you travel while reacting, then the metres your tyres need once the brakes bite. This test measures the first; your tyres decide the second.

The two compound. At 100 km/h, a driver reacting in 1.2 seconds travels about 33 metres before braking; a 0.7-second driver travels about 19 metres. That is nearly 14 metres between them before either car slows. Put worn tyres on the slower car, wet road braking can need 30 to 50 percent more distance than new tyres, and the same emergency ends more than five car lengths apart for two otherwise identical cars.

You can't buy a faster brain, but you can buy a shorter stop. Sleep and attention set your reaction; tread depth and wet grip set your braking. One of those is on our shelves.

See both halves together in the braking simulator: its engine is checked against 974 catalogued braking tests, and of the 871 that could be tested directly, 97.4 percent landed within tolerance. It is the same engine that decides how hard both cars brake in this test, which is why the wet setting here behaves like the wet setting there.

LimitsWhat 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. 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 with good tyres in good condition. An ordinary car on an ordinary road needs more room than this.
  • 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 are the 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. Only your personal best is stored, on your own device.

What the model holds constant

Everything below is fixed. That is what makes the comparison between two of your own runs fair, and it is also why the distances are optimistic against a real car on a real road. The same list is readable inside the tool while you use it.

Held constant Why it matters
Tyres as new, 8 mm The single biggest variable in braking, and it is switched off here. At the 1.5 mm legal minimum, wet braking is a different exercise entirely.
Pressure correct Under-inflation lengthens braking and heats the tyre.
Tyre age 0 years Rubber hardens as it ages, and old tread grips worse than it looks.
Wet grip grade C A mid-range EU wet grip rating. A grade A tyre stops appreciably shorter, an E appreciably longer.
1500 kg, unladen A loaded car, a full boot or a towed trailer all need more room.
ABS fitted, brakes cold No brake fade, no failures, no difference between a new car and a tired one.
Sealed asphalt No gravel, no chip seal, no painted lines, no diesel.
Flat, no camber Gradient changes stopping distance in both directions.
20 °C Cold rubber grips less. A frosty morning is not this.
Car ahead identical In reality the car in front may stop much shorter than yours, or much longer.
Straight line only No steering, no swerving, no corner.
It always stops fully The lead car brakes to a stop every time, so you are never judging a partial slow-down.
No other traffic Nothing beside you, nothing behind you, and nowhere else to look.

The tool also shows its working: every figure on the results panel can be expanded to the arithmetic behind it, so nothing on screen has to be taken on trust.

QuestionsCommon questions

The test

What is a good brake reaction time?

For a test like this one, 0.5 to 0.9 seconds is good real-world driving form and under 0.5 is exceptional. Over 1.2 seconds is worth a second run when you are fresh, because tiredness and distraction are the usual explanations. Remember that this is a best case: you knew the light was coming.

Why is my time higher than on reflex-test websites?

Those measure a twitch to a colour change, about 0.2 seconds. This test makes you recognise brake lights, reject the indicator trap, and act, which is the job your brain actually does behind a car. Comparing the two is apples and oranges.

Why the median instead of the average?

Five rounds, middle score. A single lucky anticipation or one long blink would drag an average around; the median tells you what you can actually repeat.

Why did I crash even though I braked?

Because the gap was spent before your brakes contributed anything. Both cars slow at the same rate, so the only distance you lose is the distance you travel while reacting. If your reaction is longer than the gap you set, you hit them. That is the whole lesson, and it is why the rule is taught in seconds.

How does reaction time affect stopping distance?

At 100 km/h you travel 27.8 metres per second before braking begins. A driver reacting in 1.5 seconds covers 41.7 metres; at 1.0 seconds it is 27.8 metres. Nearly 14 metres of road, decided before either brake pedal moves.
Settings and road rules

What following gap should I set?

Start with the gap you actually leave, then try it at the recommended one. New Zealand's Road Code teaches two seconds in normal conditions and four seconds when it is wet, slippery, in bad weather or when towing. Set the test to one second at 100 km/h and the reason for the extra becomes obvious quickly.

Does the wet setting model my tyres?

No. Wet uses about 1 mm of water and heavy rain about 2.5 mm, but the tyre itself is held constant at new tread and a mid-range wet grip grade. Worn tyres at the legal minimum can need 30 to 50 percent more distance in the wet, so the wet setting here is, if anything, generous. The braking simulator is the tool that models specific tyres.

Why does switching to mph not convert my speed?

Because it is a unit for the whole drive, not a conversion of one number. Selecting 100 with mph chosen gives you a 100 mph drive and reports every distance in feet. If you want the metric equivalent of a speed, choose it from the list in km/h.

Can I use it on a phone?

Yes, and the test works the same way. Use the Full screen button under View where your browser offers it, because a small stage makes the brake lights harder to spot than they should be and that lands in your result.

Is this a driving assessment?

No. It is an educational demonstration of reaction time and stopping distance. It is not a medical or cognitive test, it is not a measure of fitness to drive, and no result here should be used to judge whether anyone is safe on the road. If you are worried about your reactions, that is a conversation for your doctor, not a web page.

Your reaction is half the stop. Your tyres are the other half.

Whatever your time, worn tread spends the margin your reactions earn. Tell us what you drive and we will tell you what actually grips in the wet, fitted and balanced in Te Puke.

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About the author
TH

Taylor Houghton

Manager, Tyre Dispatch · Warehouse Manager, Traction Tyres

Petitioner to Parliament · tyre labelling Tyrewise launch video Te Puke, Bay of Plenty workshop

Taylor Houghton has spent his working life in the tyre trade, beginning in his father's tyre business at the age of five and handling import containers through his school years. He developed Tyre Dispatch, the retail arm of Traction Tyres, and now manages it alongside the Traction Tyres warehouse in Te Puke, with responsibility for buying and brand selection. He holds no ownership interest in either business.

Both brands the company distributes exclusively in New Zealand, Anchee and Predator, were his selections, each assessed on factory accreditation, compound composition and independent test data rather than name recognition. More than 100,000 Anchee tyres have since been sold here, and both brands hold five star review averages.

The guides, calculators and tools on this site are his own work, as is the workshop dataset behind them, which covers 1,700+ documented tyre inspections and 45,000+ photographs and represents more than a thousand hours, the majority outside business hours. He is the petitioner to Parliament for mandatory tyre performance labelling and minimum wet-grip standards in New Zealand, and appeared in the launch video for Tyrewise, the national tyre stewardship scheme.

Photography, measurements and advice on this site are first-hand; where a figure comes from elsewhere, it is attributed.

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