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Difficulty: MediumDriving in Fog

Heavy localized fog suddenly blankets a multi-lane bypass, significantly degrading visibility and leaving pavement damp. Which driving procedure complies with official commercial vehicle safety standards under these conditions?

  1. A
    Set the auxiliary engine retarder to maximum power to decelerate quickly on the damp road surface without using the service brakes.
  2. Operate with low-beam headlights active and reduce speed so the vehicle can come to a full stop within the visible distance ahead.Answer
  3. C
    Close the following distance to track directly behind the taillights of a preceding truck to navigate lane paths.
  4. D
    Maintain normal travel speed while relying solely on estimated braking friction distance without accounting for perception and reaction time.

Answer

Operate with low-beam headlights active and reduce speed so the vehicle can come to a full stop within the visible distance ahead.
When driving in fog, the safest course of action is to use low-beam headlights (to prevent glare reflection) and slow down sufficiently so that total stopping distance does not exceed the distance visible ahead. This ensures full control and adequate reaction space.

Step-by-Step Solution

1
Select the correct headlight setting
Low beams provide roadway illumination without causing high-beam back-scatter glare from moisture droplets.
High beams reflect light directly back into the driver's eyes, blinding the driver and reducing visibility further.
2
Manage vehicle speed relative to sight distance
The truck travels at a speed where the total stopping distance (perception + reaction + braking) is shorter than the forward visible range.
A driver must always be able to stop safely before reaching an unexpected obstacle or stopped vehicle hidden by fog.
3
Assess pavement traction and vehicle controls
Avoid aggressive braking or high retarder settings that could induce a drive-wheel skid on condensation-slicked pavement.
Fog condensation creates slick surface film that drastically reduces tire grip.

Key Concept

Operating in Reduced Visibility and Sight Distance Speed Management
Estimated Time:1m 0s
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Topics

Driving in Fog

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