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Question

Difficulty: MediumWinter Driving

A commercial motor vehicle driver encounters a shaded mountain downgrade during freezing precipitation where icy patches are forming. Arrange the following actions in the correct chronological sequence to maintain vehicle control and safely negotiate the slope according to CDL winter driving standards.

  1. 1Deactivate the engine retarder or auxiliary brake to eliminate the risk of drive-wheel skid on slippery surfaces.
  2. 2Decelerate smoothly to a safe control speed before entering the downgrade.
  3. 3Shift the transmission into a low gear that matches the reduced control speed.
  4. 4Utilize light, steady snub braking as needed while descending to keep the vehicle below the maximum safe speed.

Answer

The correct sequence is: Deactivate the engine retarder -> Decelerate smoothly to a safe control speed -> Shift the transmission into a low gear -> Utilize light, steady snub braking as needed while descending.
Under CDL winter driving procedures, a driver must first disengage auxiliary retarders whenever road surfaces are wet, icy, or snow-covered to avoid sudden drive-wheel lockup. The driver then reduces speed to a safe control level and selects a low transmission gear before beginning the descent. Once on the slope, speed is governed primarily by engine compression, with light, intermittent snub braking used as needed.

Step-by-Step Solution

1
Turn off the engine retarder / auxiliary brake.
Prevents auxiliary engine braking force from inducing a sudden drive-wheel skid on slick pavement.
Retarders apply braking torque only to the drive axles, which can break traction instantly when wheels cross ice or packed snow.
2
Reduce travel speed significantly before the downhill grade.
Establishes a safe entry speed prior to gravitational acceleration.
Stopping distances on ice can be up to ten times greater, making speed control before the descent critical.
3
Downshift the transmission into the appropriate low gear.
Engages engine compression to control descent speed without sole reliance on service brakes.
Gear selection must occur before starting down the hill to prevent gear-hunting or wheel lockup during a shift on slick road surfaces.
4
Apply light, controlled snub braking intermittently during descent.
Holds the vehicle at or below the target safe speed without locking up wheels or overheating brake linings.
Gradual snub braking maintains vehicle stability and directional control on variable winter pavement.

Key Concept

Downhill speed management and retarder deactivation procedures under winter roadway conditions
Estimated Time:1m 30s
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Topics

Winter Driving

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