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Question

Difficulty: MediumStopping Distances

You are driving an ordinary passenger car at 30 mph30\text{ mph} (48 km/h48\text{ km/h}) along a dry, level road in good weather conditions. In an emergency stop, what is the typical braking distance required for your vehicle to come to a complete standstill?

  1. A
    9 metres9\text{ metres} (30 feet30\text{ feet})
  2. 14 metres14\text{ metres} (45 feet45\text{ feet})Answer
  3. C
    23 metres23\text{ metres} (75 feet75\text{ feet})
  4. D
    28 metres28\text{ metres} (90 feet90\text{ feet})

Answer

The typical braking distance at 30 mph30\text{ mph} under dry conditions is 14 metres14\text{ metres} (45 feet45\text{ feet}).
Under normal dry conditions, a vehicle travelling at 30 mph30\text{ mph} (48 km/h48\text{ km/h}) has a thinking distance of 9 metres9\text{ metres} (30 feet30\text{ feet}) and a braking distance of 14 metres14\text{ metres} (45 feet45\text{ feet}), giving a total stopping distance of 23 metres23\text{ metres} (75 feet75\text{ feet}). Therefore, the braking distance component alone is 14 metres14\text{ metres} (45 feet45\text{ feet}).

Step-by-Step Solution

1
Identify the total stopping distance breakdown from The Highway Code for a car travelling at 30 mph30\text{ mph} (48 km/h48\text{ km/h}).
Total stopping distance is 23 metres23\text{ metres} (75 feet75\text{ feet}), comprising thinking distance and braking distance.
Stopping distance consists of two separate components: thinking distance and braking distance.
2
Determine the thinking distance component at 30 mph30\text{ mph}.
Thinking distance is 9 metres9\text{ metres} (30 feet30\text{ feet}).
At 30 mph30\text{ mph}, reaction time typically accounts for 9 metres9\text{ metres} before the brakes are applied.
3
Subtract the thinking distance from the total stopping distance to isolate the braking distance.
23 metres−9 metres=14 metres23\text{ metres} - 9\text{ metres} = 14\text{ metres} (75 feet−30 feet=45 feet75\text{ feet} - 30\text{ feet} = 45\text{ feet}).
Braking distance is the physical distance the car travels after the brake pedal is pressed until coming to a complete stop.

Key Concept

Highway Code stopping distance components at 30 mph
Estimated Time:1m 0s
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Topics

Stopping Distances

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