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Difficulty: MediumFactors Affecting Braking Distance

You are driving along a rural road that has recently been resurfaced with loose gravel chippings. How does this road surface affect your vehicle's stopping distance?

  1. A
    It increases your thinking distance because your reaction time is lengthened on an unfamiliar surface.
  2. B
    It has no effect on braking distance provided your vehicle's tyre tread depth exceeds the legal minimum.
  3. It increases your braking distance because the loose stones reduce tyre grip on the road.Answer
  4. D
    It decreases your braking distance because loose stones create extra friction against the tyres.

Answer

It increases your braking distance because the loose stones reduce tyre grip on the road.
Loose gravel chippings create an unstable road surface where stones roll between the tyre tread and the solid road beneath. This drastically lowers tyre grip and friction, requiring a significantly longer distance for the vehicle to come to a complete halt once the brakes are applied.

Step-by-Step Solution

1
Differentiate between the components of total stopping distance
Total stopping distance consists of thinking distance (driver reaction) and braking distance (vehicle deceleration distance).
Road surface characteristics affect the physical interaction between the vehicle and the ground, not human reaction time.
2
Evaluate the effect of loose gravel chippings on tyre traction
Loose stones move beneath the tyre contact patch, significantly reducing the coefficient of friction compared to solid asphalt.
Lower friction reduces braking efficiency and prolongs the distance required for the vehicle to decelerate to a complete stop.
3
Select the option that correctly attributes the effect to braking distance
The road condition increases braking distance due to reduced grip.
This accurately reflects UK Highway Code guidance on safety margins across poor or loose road surfaces.

Key Concept

Physical road surface conditions such as loose gravel, mud, or water directly reduce tyre traction and increase braking distance without altering thinking distance.
Estimated Time:1m 0s
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Topics

Factors Affecting Braking Distance

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