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Difficulty: HardSpeed Control and Following Distance

A driver operating a passenger vehicle while towing a heavy travel trailer is descending a steep downgrade on a highway during a rain shower. Traffic ahead is moving near the posted maximum speed limit of 55 mph55\text{ mph}. Under safe driving practices and the Basic Speed Law, how should the driver manage their vehicle speed and following distance?

  1. Reduce speed below the posted limit and increase following distance to at least 55 to 66 seconds to compensate for reduced traction and increased vehicle momentum.Answer
  2. B
    Maintain the posted speed limit of 55 mph55\text{ mph} while keeping a standard 33-second following distance, since posted limits establish the legally safe speed for all vehicle types regardless of weather or load.
  3. C
    Maintain the posted speed limit of 55 mph55\text{ mph} while expanding following distance to 66 seconds, because speed reductions are legally required only when visibility falls below 500 feet500\text{ feet}.
  4. D
    Reduce speed below the posted limit while maintaining the standard 33-second following distance, as slowing down fully neutralizes the additional stopping distance caused by the trailer.

Answer

Reduce speed below the posted limit and increase following distance to at least 55 to 66 seconds to compensate for reduced traction and increased vehicle momentum.
Under the Basic Speed Law, drivers must adjust their speed according to weather, road gradient, and vehicle loading. Towing a trailer down a wet, steep grade increases momentum and significantly lengthens stopping distance. Safe vehicle control requires both reducing speed below the posted maximum and increasing following distance to at least 55 to 66 seconds.

Step-by-Step Solution

1
Identify compound hazard factors affecting vehicle control.
Recognized three compounding risk factors: increased weight/momentum from towing, gravitational acceleration on a downhill grade, and reduced tire grip on wet pavement.
Each factor prolongs braking distance and impairs steering stability.
2
Apply the Basic Speed Law.
Determine that driving at the posted maximum limit of 55 mph55\text{ mph} is unsafe for these specific physical conditions.
The Basic Speed Law requires driving at a speed that is reasonable and prudent for existing road, weather, and vehicle load conditions.
3
Calculate the appropriate following distance cushion.
Extend the baseline 33-second following distance to a minimum of 55 to 66 seconds.
Heavy combination vehicles on wet downhill slopes require substantially greater distance to come to a complete emergency stop.

Key Concept

Basic Speed Law compliance and following distance expansion under compounding hazard conditions (towing + steep grade + wet pavement).
Estimated Time:2m 0s
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Topics

Speed Control and Following Distance

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