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Zorluk: OrtaSpeed and Road Conditions

A commercial truck is traveling at a posted speed of 60 mph60\text{ mph} on a rural expressway when a heavy downpour causes water to accumulate on the road surface. According to commercial driving safety standards for wet pavement, which action should the driver take to maintain vehicle control and prevent traction loss?

  1. A
    Maintain the current speed of 60 mph60\text{ mph} but increase following distance, relying on the vehicle's air brake system to handle any sudden stops.
  2. Reduce speed by approximately one-third to about 40 mph40\text{ mph} and turn off the engine retarder.Cevap
  3. C
    Slow down to 40 mph40\text{ mph} while setting the engine brake or retarder to maximum power to assist in continuous slowing.
  4. D
    Maintain highway speed until encountering standing water or a sharp bend, then apply the service brakes firmly to decelerate.

Cevap

Reduce speed by approximately one-third to about 40 mph40\text{ mph} and turn off the engine retarder.
On wet pavement, traction is significantly reduced, requiring commercial drivers to slow down by about one-third of their dry-road speed (e.g., from 60 mph60\text{ mph} to about 40 mph40\text{ mph}). Furthermore, engine retarders must always be switched off whenever roads are wet, icy, or snow-covered because retarder braking force can easily lock the drive wheels and provoke a jackknife.

Adım Adım Çözüm

1
Calculate the required wet-road speed reduction.
A one-third reduction from 60 mph60\text{ mph} yields a target operating speed of approximately 40 mph40\text{ mph} (60−20=4060 - 20 = 40).
Commercial driver safety guidelines require reducing speed by about one-third on wet pavement to prevent hydroplaning and manage extended stopping distances.
2
Evaluate auxiliary braking systems (engine retarders) for wet road conditions.
Engine retarders must be disabled.
Retarder braking force applied only to drive wheels on slippery or wet surfaces can cause the drive tires to lose grip, initiating a skid or jackknife.

Anahtar Kavram

Speed reduction and auxiliary braking safety on wet road surfaces
Tahmini Süre:1m 0s
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