Interactive tool
Stopping distance simulator
Move the sliders and watch how far your car really travels before it stops. Speed, your reaction time and the road surface each change the answer — often by more than drivers expect.
Section 1
Try it yourself
The amber stretch is the distance you cover while you react — before the brakes even touch. The red stretch is the actual braking. Together they are your real stopping distance.
From a 30 km/h housing estate to 120 km/h motorway.
0.67 s is the official Highway Code figure for an alert driver. Real-world reaction is often 1.0 s, and 1.5–2.5 s when tired or distracted.
Section 2
Why the numbers move the way they do
Stopping distance is two separate things added together. They behave very differently as speed rises.
Thinking distance grows with speed
This is how far you travel during your reaction time — from seeing the hazard to pressing the pedal. Because it is simply speed multiplied by time, it grows in a straight line: double the speed and you double this distance.
thinking = speed × reaction timeBraking distance grows with speed squared
This is the killer. A moving car carries kinetic energy proportional to the square of its speed, and the brakes have to shed all of it. Double the speed and braking distance roughly quadruples. This is why a small speed increase has a large effect on whether you stop in time.
braking = speed² ÷ (2 × grip × g)The surface penalty applies to the braking part only. The Highway Code advises that braking distance roughly doubles in the wet and can be up to ten times greater on ice or snow. Your thinking distance does not change with the weather — your reaction time is the same — but the distance needed to actually stop grows dramatically.
Section 3
Stopping distance at a glance
Dry-road figures for an alert driver (0.67-second reaction). These reproduce the official RSA Rules of the Road / Highway Code stopping distances. Notice how the total climbs far faster than the speed.
| Speed | Thinking | Braking (dry) | Total (dry) | Total (wet) | ≈ Car lengths (dry) |
|---|
Rounded to the nearest metre. These are the official figures for good conditions — treat them as a minimum. Real distances vary with the vehicle, tyres, brakes, load, gradient and exact surface, and increase sharply once your reaction time rises above 0.67 s. One car length ≈ 4.5 m.
Section 4
What this means for your following gap
Stopping distance is only half the story behind the two-second rule. Here is how they connect.
The two-second rule buys reaction time
A two-second gap to the car ahead covers roughly your thinking distance — the time to notice the car in front braking and to respond. It assumes the car ahead is also braking, not a stationary wall. It is a minimum, not a comfort margin.
An emergency stop needs the full distance
If the hazard is stationary — a stopped queue, a fallen object, a pedestrian — you need the whole stopping distance shown in the simulator, not just two seconds. In the wet, double the gap. On ice, leave a vast margin or slow right down.
Want the full picture on safe following distance?
Our research-led review digs into where the two-second rule comes from, when it holds, and when it quietly fails — using RSA, Roadcraft and MIT human-factors data.
Read the Two-Second Rule reviewSection 5
Common questions
Are these the official Rules of the Road figures?
Yes. At the default settings — an alert driver (0.67 s reaction) on a dry road — the tool reproduces the stopping distances published in the RSA Rules of the Road and the UK Highway Code (for example, 12 m at 32 km/h, 53 m at 80 km/h and 96 m at 113 km/h). The wet and ice/snow options apply the braking-distance multipliers those guides use: roughly ×2 in the wet and up to ×10 on ice or snow. We then let you raise the reaction time so you can see how quickly the distance grows when attention slips.
Why does my real reaction time matter so much?
The published figures assume an alert driver reacting in around two-thirds of a second to one second. A tired, distracted or phone-using driver can take two seconds or more. Slide the reaction control to 2.0 s and watch the thinking distance balloon — at motorway speed that alone can be tens of metres of road covered before you have even touched the brake.
Does ABS or a newer car shorten this?
ABS helps you steer while braking hard and stops the wheels locking, but it does not defeat physics — grip is grip. On a dry road the difference in distance is small; its real value is on slippery surfaces and in keeping control. Good tyres, correct pressures and a well-maintained braking system matter more to the actual distance than the badge on the car.
How does this connect to my lessons?
Reading distance and managing speed before hazards is core to passing your test and to driving safely afterwards. We coach observation, the system of car control and realistic speed choice on every lesson. If you want to understand the deeper mechanics, pair this tool with our physics of braking and cornering guide.
At the default settings the figures match the published values for good conditions; treat them as a minimum. Educational tool only — does not replace statutory guidance or qualified instruction.