Stopping Distance Simulator

See how much further you travel before stopping as speed increases.

A key relationship tested on the written exam: braking distance is proportional to the SQUARE of speed. Double your speed and braking distance roughly quadruples; triple it and it roughly multiplies by nine. Pick two speeds below to compare (shown as a multiplier, not meters — the exact distance depends on road surface, tires and vehicle weight).

Braking distance at 100 km/h is about 2.8× that at 60 km/h

We only show a multiplier here, not meters — the exact distance depends heavily on road surface, tires and vehicle weight.

Speed & stopping distance

Legal speed limits by road and vehicle type, and the two components of stopping distance.

Tips & tricks

  • Stopping distance = reaction distance (how far you travel before braking starts) + braking distance (from brakes engaging to a full stop). Knowing this split is the whole point of many questions.
  • Both braking distance and centrifugal force scale with the SQUARE of speed — double the speed means roughly 4x the distance or force, not 2x.
  • Default limits: 60 km/h for cars on ordinary roads, 30 km/h for mopeds. A moped can never legally exceed 30 km/h even if a sign posts a higher limit.

Important notes

  • A legal minimum speed (50 km/h) exists only on the main carriageway of expressways — never on ordinary roads.
  • "Under the speed limit is always safe" is false — rain, night, and traffic density all call for slowing further below the posted limit.
  • A wet road or worn tires can roughly double your braking distance compared with dry pavement.

Numbers worth remembering

  • 60 km/h — What is the statutory maximum speed for a car on an ordinary road?
    60 km/h on an ordinary road. Where a sign posts a limit, follow the sign instead.
  • 30 km/h — What is the statutory maximum speed for a moped?
    30 km/h. Even where a sign posts 40 or 50, a moped may not exceed 30.
  • 4× — If your speed doubles, roughly how many times longer is the braking distance?
    About four times — braking distance is proportional to the square of speed. Centrifugal force and impact force scale the same way.
  • 2× — On a wet road, the braking distance can be roughly how many times that of a dry road?
    About twice — the tires grip less. Slow down and leave a longer gap.
Practice with the Number Drill mode

Karimen vs honmen vs gaimen kirikae

Key Numbers to MemorizeThe distances, speeds and time limits the written test asks about, grouped by topic so you don't mix up the similar ones.Japanese Traffic RulesThe traffic rules that come up most in the written test, organized by topic. Road signs have their own page.