Braking Distance

Braking distance grows with the square of speed:

• 2× the speed = 4× the braking distance.
• 3× the speed = 9× the braking distance.

Sit with that, because it's the single most consequential fact in this module, and it's the one human intuition gets wrong. Intuition scales linearly: a bit faster, a bit longer to stop. Physics disagrees — kinetic energy grows with speed squared, and your brakes must dissipate all of it. Going from 50 to 100 km/h doesn't double your braking distance; it quadruples it.

[DIAGRAM: braking-distance-quadratic — see SVG below]

This is also the honest answer to "it's only 10 km/h over." From 50 to 60 km/h, braking distance grows not by 20% but by 44% (6²/5² = 36/25). The overage feels trivial in the seat; it isn't trivial in metres.

What else affects it: the road's gradient and condition, the load, and the brakes themselves — condition, technique, and how many wheels are doing the work.

Calculating it — the mental-math method (dry road, good tyres, good brakes):

1. Remove the last digit of your speed. (50 → 5)
2. Multiply the figure by itself. (5 × 5 = 25)
3. Multiply by 0.4. (= 10 metres at 50 km/h, dry)

The 0.4 is empirical: measured braking distance from 10 km/h on dry tarmac is about 0.4 m, and everything above scales quadratically from there.

The precise formula: distance = speed² ÷ (250 × f), where f is the friction coefficient — roughly 0.8 on dry tarmac and as low as 0.1 on ice. Kenya has no ice, but the span is the lesson: braking distance can stretch to many times its dry value purely from what's under the tyres, before you or your car change at all.