KSA Driving Theory Practice

Stopping Distance: Formula and Table

Stopping distance is the distance your car travels from the moment you notice a danger until it comes to a complete stop. It has two parts: the reaction distance, covered while you react before braking, and the braking distance, covered after you press the brake. The KSA driving handbook gives simple formulas to estimate both in metres from your speed in km/h.

Road diagram: a car and an obstacle, with points marked Hazard seen, Brake pressed and Car stops, and arrows A, B and C between them

The formulas

Stopping distance = reaction distance + braking distance

Reaction distance = (Speed / 10) x 3

Braking distance = (Speed / 10) x (Speed / 10)

The reaction distance assumes a standard reaction time of one second. The braking distance assumes hard braking on a dry road. Because braking distance grows with the square of your speed, doubling your speed makes it about four times longer (Handbook p. 16).

Stopping distance table

Reaction, braking and stopping distance by speed
SpeedReactionBrakingStopping
30 km/h9 m9 m18 m
40 km/h12 m16 m28 m
50 km/h15 m25 m40 m
60 km/h18 m36 m54 m
70 km/h21 m49 m70 m
80 km/h24 m64 m88 m
90 km/h27 m81 m108 m
100 km/h30 m100 m130 m
110 km/h33 m121 m154 m
120 km/h36 m144 m180 m

Calculated with the handbook formulas above (Handbook p. 16).

What makes the distances longer

Speed & Stopping DistanceWhich of these makes the REACTION distance longer?

  1. AThe vehicle is heavily loaded
  2. BThe road is wet
  3. CThe tires are worn
  4. DThe driver is tired or distracted (correct answer)

Correct answer: D. Tiredness or distraction slows your reaction. Wet roads, heavy loads and worn tires lengthen the braking distance instead.Source: Handbook p. 14 · View in topic

Speed & Stopping DistanceWhich of these makes the reaction distance longer?

  1. ACarrying a heavy load
  2. BHaving weak brakes
  3. CDriving on a sandy road
  4. DTaking medicine that causes drowsiness (correct answer)

Correct answer: D. Drugs or medicine causing drowsiness, alcohol, tiredness, distraction and high speed lengthen reaction distance. The others affect braking distance.Source: Handbook p. 14 · View in topic

Speed & Stopping DistanceWhich factor increases BOTH the reaction distance and the braking distance?

  1. AA wet road
  2. BHigh speed (correct answer)
  3. CTiredness
  4. DA heavy load

Correct answer: B. High speed is listed for both. Tiredness affects only reaction distance; a wet road and heavy load affect only braking distance.Source: Handbook p. 14 · View in topic

Speed & Stopping DistanceWhich of these makes the BRAKING distance longer?

  1. AA tired driver
  2. BA distracted driver
  3. CA heavily loaded vehicle (correct answer)
  4. DA driver under the influence of alcohol

Correct answer: C. A heavy load lengthens braking distance. The other three lengthen reaction distance.Source: Handbook p. 15 · View in topic

Speed & Stopping DistanceSand, snow or a wet road surface mainly increases:

  1. AThe driver's reaction time
  2. BThe reaction distance
  3. CNothing, if the tires are new
  4. DThe braking distance (correct answer)

Correct answer: D. Poor road conditions such as sand, snow or a wet surface make the braking distance longer.Source: Handbook p. 15 · View in topic

Speed & Stopping DistanceWhich vehicle condition makes the braking distance longer?

  1. AWorking headlights
  2. BBad tires or malfunctioning brakes (correct answer)
  3. CA full windscreen washer tank
  4. DA clean windshield

Correct answer: B. Bad tires and malfunctioning or insufficient brakes both lengthen braking distance.Source: Handbook p. 15 · View in topic

Speed & Stopping DistanceHow can you reduce your stopping distance?

  1. AReduce speed and increase attention (correct answer)
  2. BIncrease tire pressure above the recommended level
  3. CFollow the vehicle ahead more closely
  4. DBrake later but harder

Correct answer: A. The handbook lists two ways: reduce speed and increase attention.Source: Handbook p. 17 · View in topic

Practise speed and stopping questions →