Examkin

Soru

Zorluk: ZorSpeed and Road Conditions

A commercial driver is operating a loaded vehicle at 40 mph on a roadway that transitions to packed snow leading toward an elevated bridge and curve. Which combination of speed adjustment and vehicle control actions is required to safely navigate this section?

  1. A
    Reduce vehicle speed to approximately 27 mph before the bridge, keeping the engine retarder engaged while calculating stopping requirements based only on braking distance.
  2. Reduce vehicle speed to 20 mph or less before entering the curve and bridge, and ensure the engine retarder is switched off.Cevap
  3. C
    Engage the engine retarder to maximum to decelerate to 20 mph before the bridge, relying on retarder back-pressure to maintain drive-wheel traction.
  4. D
    Maintain 40 mph until reaching the bridge, then apply firm, continuous service brakes throughout the curve to bring the vehicle down to 20 mph.

Cevap

Reduce vehicle speed to 20 mph or less before entering the curve and bridge, and ensure the engine retarder is switched off.
According to commercial driving safety regulations, operating on packed snow requires a speed reduction of at least one-half (from 40 mph down to 20 mph or less). This speed reduction must be completed prior to entering any curve or elevated structure (which freezes before other roadway sections). In addition, engine retarders must be turned off whenever road surfaces are slippery or covered with snow/ice to eliminate the risk of drive-wheel lockup and sudden jackknife.

Adım Adım Çözüm

1
Calculate the mandatory speed reduction for packed snow.
Reduce speed by at least 1/2 from 40 mph to 20 mph or slower.
Official commercial driving standards require reducing road speed by half or more on packed snow due to drastically reduced tire traction.
2
Determine the required retarder setting for slippery road conditions.
Switch off and disable all engine retarders.
Retarders apply strong mechanical braking force solely to the drive axles; on slippery surfaces like snow or ice, this causes drive-wheel lockup and immediate skidding.
3
Identify the proper timing and location for braking ahead of a curve and overpass.
Complete all deceleration before reaching the bridge and entering the curve.
Braking inside a turn diverts available traction from lateral steering to braking, precipitating a spin-out or rollover.

Anahtar Kavram

Traction-appropriate speed reduction and retarder deactivation on winter road surfaces
Tahmini Süre:1m 30s
Bu soruyu puanla

Konular

Speed and Road Conditions

Bu konudan daha fazla soru