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Difficulty: HardStopping Distances

A car accelerates from 30 mph30\text{ mph} (48 km/h48\text{ km/h}) to 60 mph60\text{ mph} (97 km/h97\text{ km/h}) on a dry road. According to The Highway Code, by how much does the vehicle's braking distance increase?

  1. A
    9 metres9\text{ metres} (30 feet30\text{ feet})
  2. B
    50 metres50\text{ metres} (165 feet165\text{ feet})
  3. 41 metres41\text{ metres} (135 feet135\text{ feet})Answer
  4. D
    28 metres28\text{ metres} (90 feet90\text{ feet})

Answer

41 metres41\text{ metres} (135 feet135\text{ feet})
According to The Highway Code, braking distance is the distance a vehicle travels after the brakes are applied until it stops. At 30 mph30\text{ mph}, the standard braking distance is 14 metres14\text{ metres} (45 feet45\text{ feet}). At 60 mph60\text{ mph}, the standard braking distance is 55 metres55\text{ metres} (180 feet180\text{ feet}). The increase in braking distance is 55 m−14 m=41 metres55\text{ m} - 14\text{ m} = 41\text{ metres} (180 ft−45 ft=135 feet180\text{ ft} - 45\text{ ft} = 135\text{ feet}).

Step-by-Step Solution

1
Identify the braking distance at 30 mph30\text{ mph} according to The Highway Code.
Braking distance at 30 mph30\text{ mph} is 14 metres14\text{ metres} (45 feet45\text{ feet}).
At 30 mph30\text{ mph}, the total stopping distance of 23 metres23\text{ metres} comprises 9 metres9\text{ metres} thinking distance and 14 metres14\text{ metres} braking distance.
2
Identify the braking distance at 60 mph60\text{ mph} according to The Highway Code.
Braking distance at 60 mph60\text{ mph} is 55 metres55\text{ metres} (180 feet180\text{ feet}).
At 60 mph60\text{ mph}, the total stopping distance of 73 metres73\text{ metres} comprises 18 metres18\text{ metres} thinking distance and 55 metres55\text{ metres} braking distance.
3
Calculate the difference between the two braking distances.
55 metres−14 metres=41 metres55\text{ metres} - 14\text{ metres} = 41\text{ metres} (180 feet−45 feet=135 feet180\text{ feet} - 45\text{ feet} = 135\text{ feet}).
Subtracting the initial braking distance from the final braking distance yields the exact increase in braking distance alone.

Key Concept

Calculating changes in braking distance independently from thinking distance across different speeds under UK Highway Code standards
Estimated Time:2m 0s
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Topics

Stopping Distances

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