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Difficulty: MediumDriving in Fog

A tractor-trailer operator navigating a rural two-lane highway before dawn encounters sudden patches of fog that leave a layer of moisture on the pavement. Which operating practice should the driver follow to maintain safe vehicle control?

  1. A
    Engage the auxiliary engine retarder to maximum power to assist in braking without using the foot brake on damp surfaces.
  2. Use low-beam headlights, switch off the engine retarder, and adjust speed so the vehicle can stop within the distance clearly visible ahead.Answer
  3. C
    Close the gap behind the preceding vehicle to use its taillights as a primary navigational guide through dense patches.
  4. D
    Maintain standard cruising speed while relying strictly on active braking distance calculations to stop for potential roadway hazards.

Answer

Use low-beam headlights, switch off the engine retarder, and adjust speed so the vehicle can stop within the distance clearly visible ahead.
According to commercial driving safety regulations, operating in fog requires using low-beam headlights to avoid glare, disengaging auxiliary retarders when moisture makes pavement slick to prevent drive-wheel skids, and reducing speed so total stopping distance never exceeds visible sight distance.

Step-by-Step Solution

1
Select proper lighting configuration
Low-beam headlights illuminate the roadway without causing severe back-reflection from suspended water droplets.
High beams reflect light directly back into the driver's eyes in fog, blinding the operator.
2
Deactivate auxiliary braking systems
Drive wheels maintain traction on moisture-slicked pavement without unexpected wheel lockup.
Retarders apply braking force only to drive axles, which readily induces skids on damp or wet road surfaces.
3
Calibrate travel speed to forward sight distance
Total stopping distance (perception + reaction + braking) remains strictly less than the visible forward path.
Driving faster than the distance one can see ahead makes collisions unavoidable when an unexpected hazard appears.

Key Concept

Defensive speed adjustment, lighting choice, and retarder disengagement when operating commercial motor vehicles in fog and slick conditions.
Estimated Time:1m 0s
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Topics

Driving in Fog

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