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Question

Difficulty: EasyCoasting and Engine Braking

Why is coasting (travelling downhill in neutral or with the clutch pedal held down) dangerous?

  1. A
    It applies sudden engine braking that can induce a skid
  2. It reduces vehicle control and can cause the brakes to overheatAnswer
  3. C
    It directly increases driver reaction time and thinking distance
  4. D
    It immediately locks the steering mechanism while in motion

Answer

It reduces vehicle control and can cause the brakes to overheat
When a vehicle is coasting, the engine is disconnected from the driven wheels. On a downhill gradient, the lack of engine braking allows the vehicle to pick up speed quickly. This forces the driver to rely solely on the footbrake, which can overheat and become less effective (brake fade), whilst also reducing steering stability.

Step-by-Step Solution

1
Identify the mechanical consequence of coasting
Pressing the clutch or selecting neutral disconnects the engine from the transmission, removing engine braking.
Engine braking naturally helps regulate vehicle speed when descending slopes.
2
Determine the impact on vehicle braking systems on a descent
The driver must rely entirely on the footbrake, leading to brake overheating and reduced vehicle control.
Continuous friction on the brake discs causes brake fade, diminishing stopping efficiency.

Key Concept

Loss of engine braking and risks of coasting downhill
Estimated Time:45s
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Topics

Coasting and Engine Braking

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