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Zorluk: OrtaWinter Driving

A commercial driver is operating a combination vehicle on a rural highway with patches of packed snow and ice. During the afternoon, the ambient temperature increases from 20∘F20^\circ\text{F} to 32∘F32^\circ\text{F} (−7∘C-7^\circ\text{C} to 0∘F0^\circ\text{F}), causing a thin film of water to form over the icy road surface. Which of the following statements correctly describes the effect of this temperature change on traction and the proper driver response?

  1. A
    Traction decreases because wet ice is more slippery than dry ice; the driver should maintain highway cruising speed while engaging the engine retarder to its highest setting to assist service brakes.
  2. Traction decreases significantly because wet ice is much more slippery than ice at colder temperatures; the driver should reduce speed to a crawl, increase following distance, and ensure the engine retarder is turned off.Cevap
  3. C
    Traction remains unchanged because ice provides identical friction across all sub-freezing temperatures; the driver should continue at normal speed while maintaining the standard dry-pavement following distance of one second per 10 feet of vehicle length.
  4. D
    Traction increases as the softening surface allows steer tires with 2/32-inch tread depth to channel away slush; the driver should accelerate slightly to clear the melting sections.

Cevap

Traction decreases significantly because wet ice is much more slippery than ice at colder temperatures; the driver should reduce speed to a crawl, increase following distance, and ensure the engine retarder is turned off.
According to commercial driving safety principles, ice is most slippery when the temperature is right around the freezing point (32∘F32^\circ\text{F} / 0∘C0^\circ\text{C}) because a layer of water forms on top of the ice. In these conditions, drivers must reduce vehicle speed to a crawl, increase following distance substantially, and turn off all auxiliary retarders to prevent drive wheels from skidding.

Adım Adım Çözüm

1
Analyze the physical effect of the temperature change on icy road surfaces.
As temperature reaches the freezing point (32∘F32^\circ\text{F} / 0∘C0^\circ\text{C}), ice begins to melt, creating a thin water layer that drastically reduces tire-to-surface coefficient of friction compared to colder, dry ice.
Commercial driver safety manuals emphasize that 'wet ice' is far more dangerous and slippery than ice at lower temperatures.
2
Determine the required speed, space, and auxiliary brake adjustments.
The driver must slow the vehicle to a crawl, dramatically expand following distance, and deactivate engine retarders.
Retarder application on icy drive wheels removes traction instantly and can cause an unrecoverable jackknife.

Anahtar Kavram

Friction dynamics of wet ice at freezing temperatures and auxiliary brake management
Tahmini Süre:1m 15s
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Winter Driving

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