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Difficulty: MediumSpeed on Curves and Downgrades

When descending a steep grade with a designated safe speed of 40 mph, which braking procedure correctly describes the proper snub braking technique to control vehicle speed?

  1. A
    Apply light, continuous brake pedal pressure to maintain a steady speed of exactly 40 mph throughout the entire downgrade.
  2. Apply the brakes firmly to slow the vehicle down to 35 mph, release them completely, and reapply firmly once speed builds back up to 40 mph.Answer
  3. C
    Allow vehicle speed to reach 45 mph, then apply maximum emergency braking force until the speed drops to 25 mph before releasing.
  4. D
    Engage engine retarders at maximum strength on wet or icy pavement to hold 40 mph without utilizing the service brakes.

Answer

Apply the brakes firmly to reduce speed to 35 mph, release them completely, and reapply once speed reaches 40 mph.
Proper snub braking requires applying the service brakes with enough force to feel a definite slowdown until speed reaches 5 mph below the designated safe speed (from 40 mph down to 35 mph in approximately three seconds), then releasing the pedal completely until speed returns to 40 mph. This cycling gives brake linings and drums regular opportunities to dissipate heat, preventing thermal brake fade.

Step-by-Step Solution

1
Establish the safe descent speed based on gross weight, grade steepness, road conditions, and weather.
The target safe speed is established at 40 mph in the proper low transmission gear.
The transmission must provide the primary braking effect before auxiliary or service brakes are used.
2
Allow the vehicle to reach the safe speed of 40 mph, then apply service brakes with moderate firmness until the speed drops 5 mph below safe speed (35 mph).
Vehicle speed decreases to 35 mph in approximately three seconds.
Firm application dissipates momentum efficiently while minimizing continuous rubbing friction.
3
Release the brake pedal completely until road speed climbs back to 40 mph, then repeat the cycle.
Brakes cool down during the release intervals while the low gear holds speed in check.
The intermittent release cycle prevents brake drum and lining overheating, eliminating brake fade.

Key Concept

Proper snub braking technique on steep downgrades
Estimated Time:1m 0s
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Topics

Speed on Curves and Downgrades

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