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Question

Difficulty: MediumFactors Affecting Thinking Distance

A motorist driving through an urban shopping street suddenly notices a pedestrian stepping off the kerb ahead. Which factor will increase the distance the vehicle travels before the motorist can react and press the footbrake?

  1. A
    Driving on a road surface covered with loose gravel
  2. B
    Travelling with tyres that are worn below the legal tread depth
  3. Driving while suffering from an illness that slows mental reaction timesAnswer
  4. D
    Driving on a wet asphalt surface following a heavy rain shower

Answer

Driving while suffering from an illness that slows mental reaction times
Thinking distance is determined strictly by the vehicle's speed and the driver's reaction time. Being unwell, fatigued, distracted, or under the influence of medication slows cognitive processing and physical reflexes, which directly increases the distance covered before the driver can begin braking.

Step-by-Step Solution

1
Identify the specific component of total stopping distance being questioned
The question asks specifically about the interval before the footbrake is applied, which defines thinking distance (reaction time multiplied by vehicle speed).
Total stopping distance consists of two independent components: thinking distance and braking distance.
2
Evaluate the provided factors to distinguish driver-related influences from vehicle/environmental influences
Road surface condition, rain, and tyre wear affect mechanical friction and braking distance, whereas illness affects the driver's brain processing speed and physical response.
Only factors influencing the driver's alertness, perception, or physical reaction speed can alter thinking distance at a given speed.

Key Concept

Thinking distance is the distance travelled during the driver's reaction time; it is solely affected by the vehicle's speed and factors influencing driver reaction capability (e.g., tiredness, illness, alcohol, drugs, and distractions).
Estimated Time:45s
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Factors Affecting Thinking Distance

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