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Difficulty: MediumStopping Distances

You are driving at 30 mph30\text{ mph} (48 km/h48\text{ km/h}) on a road covered in smooth ice. According to The Official Highway Code, the typical overall stopping distance on a dry road at this speed is 23 metres23\text{ metres} (75 feet75\text{ feet}). What is the maximum total stopping distance you should allow for in these icy conditions?

  1. A
    46 metres46\text{ metres} (150 feet150\text{ feet})
  2. B
    92 metres92\text{ metres} (300 feet300\text{ feet})
  3. 230 metres230\text{ metres} (750 feet750\text{ feet})Answer
  4. D
    115 metres115\text{ metres} (375 feet375\text{ feet})

Answer

230 metres230\text{ metres} (750 feet750\text{ feet})
According to The Official Highway Code, stopping distances on icy roads can increase by up to ten times compared to dry conditions. For a vehicle travelling at 30 mph30\text{ mph} where the baseline dry stopping distance is 23 metres23\text{ metres} (75 feet75\text{ feet}), multiplying by 1010 yields a maximum distance of 230 metres230\text{ metres} (750 feet750\text{ feet}).

Step-by-Step Solution

1
Identify the base stopping distance for the given speed under normal conditions
At 30 mph30\text{ mph} (48 km/h48\text{ km/h}), the standard stopping distance on a dry road is 23 metres23\text{ metres} (75 feet75\text{ feet}).
The baseline stopping distance consists of 9 metres9\text{ metres} thinking distance plus 14 metres14\text{ metres} braking distance.
2
Apply the official environmental multiplier for ice and snow according to The Highway Code
Icy conditions increase stopping distances by up to 1010 times (10×10\times).
Severe loss of tyre friction drastically lengthens braking distance.
3
Calculate the total required stopping distance on ice
23 metres×10=230 metres23\text{ metres} \times 10 = 230\text{ metres} (75 feet×10=750 feet75\text{ feet} \times 10 = 750\text{ feet}).
Multiplying the base distance by 1010 provides the maximum expected stopping distance.

Key Concept

Highway Code stopping distances under adverse weather conditions (tenfold increase on ice)
Estimated Time:1m 0s
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Topics

Stopping Distances

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