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Question

Difficulty: MediumNight Driving

You are operating a commercial motor vehicle at night on an unlighted rural highway with low beams engaged. To maintain safe speed management and prevent overdriving the headlights, which operational rule must you follow?

  1. A
    Calculate safe traveling speed using vehicle braking distance alone, omitting perception and reaction distances from your stopping margin.
  2. Adjust your speed so that total stopping distance is always within the distance illuminated by your headlights.Answer
  3. C
    Maintain daytime cruising speeds as long as you establish a standard three-second following distance behind forward traffic.
  4. D
    Set your traveling speed so that total stopping distance equals twice the forward distance illuminated by your headlight beams.

Answer

Adjust your speed so that total stopping distance is always within the distance illuminated by your headlights.
According to commercial driving safety principles, a driver must never overdrive their headlights. The vehicle's total stopping distance (the sum of perception distance, reaction distance, and braking distance) must never exceed the distance illuminated by the headlights so the driver can stop safely for unexpected roadway hazards.

Step-by-Step Solution

1
Identify the nighttime visibility constraint and hazard.
Low-beam headlights provide a finite illumination envelope (typically 250 feet), limiting how far ahead roadway hazards can be identified.
At night, a driver cannot react to or brake for an obstacle until it enters the field of illumination.
2
Evaluate the definition and danger of overdriving headlights.
Overdriving headlights occurs when total stopping distance exceeds the sight distance provided by the headlights.
If total stopping distance is greater than the illuminated range, a collision is unavoidable if a stationary hazard lies directly ahead in the dark.
3
Determine the proper operational rule for night speed control.
The driver must regulate speed such that perception distance + reaction distance + braking distance is less than or equal to headlight sight distance.
This guarantees the driver has sufficient distance to detect, react, and stop safely before reaching any hazard.

Key Concept

Headlight sight distance and stopping envelope management
Estimated Time:1m 0s
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Topics

Night Driving

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