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Difficulty: MediumMountain Driving and Steep Downgrades

A driver is navigating a loaded tanker with a gross weight of 68000 lbs68{}000\text{ lbs} along an 88-mile, 6%6\% mountain downgrade on dry pavement. Halfway down the descent, the driver feels the brake pedal become increasingly soft and notices that repeated applications fail to slow the vehicle, indicating severe brake fade. If a runaway truck escape ramp is visible 12 mile\frac{1}{2}\text{ mile} ahead, which action should the driver take immediately?

  1. A
    Remain in the highway travel lane and apply continuous, heavy pressure to the brake pedal in an effort to regain friction.
  2. B
    Steer onto the paved shoulder and attempt to coast until reaching a level section of the highway.
  3. Steer the vehicle directly onto the escape ramp to bring the truck to a safe stop.Answer
  4. D
    Engage the auxiliary retarder at its highest setting while rapidly pumping the service brakes to clear heat buildup.

Answer

Steer the vehicle directly onto the escape ramp to bring the truck to a safe stop.
When foundation brakes suffer severe brake fade or total failure on a long mountain descent, the driver must immediately steer into an available runaway truck escape ramp. Escape ramps use loose material such as deep gravel, sand beds, or ascending gravity ramps to safely dissipate vehicle kinetic energy and bring the commercial motor vehicle to a complete stop without endangering other highway users.

Step-by-Step Solution

1
Identify the symptoms of brake fade on a steep mountain descent.
Recognize that a spongy pedal and diminished deceleration mean the foundation brakes are overheated and unable to control vehicle speed.
Excessive heat causes brake drums to expand and friction material to glaze, resulting in loss of stopping power.
2
Locate and evaluate available emergency runaway facilities.
Spot the designated runaway truck escape ramp located ahead on the downgrade.
Escape ramps are engineered to safely absorb vehicle kinetic energy without causing a rollover or high-speed collision.
3
Commit the vehicle to the escape ramp immediately.
The truck enters the gravel bed or arrester system and comes to a controlled stop.
Delaying escape ramp entry or attempting alternative maneuvers on the highway leads to catastrophic runaway crashes.

Key Concept

Immediate utilization of runaway truck escape ramps upon experiencing brake fade or failure on steep downgrades.
Estimated Time:1m 0s
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Topics

Mountain Driving and Steep Downgrades

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