Examkin

Question

Difficulty: MediumBrake Failure

You are driving a delivery truck when the service brakes fail completely upon approaching a downhill curve. In what sequence should you perform emergency control measures to safely decelerate and stop the vehicle?

  1. 1Downshift the transmission into a lower gear to maximize engine compression braking.
  2. 2Pump the brake pedal rapidly to generate any residual hydraulic pressure.
  3. 3Apply the parking brake progressively while holding the release control to prevent drive-wheel lockup.
  4. 4Direct the vehicle toward an open escape path, such as an uphill bank or clear shoulder, to come to a complete rest.

Answer

Downshift the transmission into a lower gear, pump the brake pedal rapidly, apply the parking brake progressively while holding the release control, and direct the vehicle toward an open escape path.
When commercial vehicle service brakes fail, standard emergency procedure requires immediately downshifting to harness engine compression braking, pumping the pedal to restore any remaining hydraulic pressure, using the parking brake with manual release control to modulate deceleration, and ultimately steering into an escape route to halt safely.

Step-by-Step Solution

1
Downshift into a lower gear.
Engages engine braking to counter acceleration before road speed climbs too high for gear synchronization.
Engine retarding force provides immediate, non-friction deceleration without risking brake overheating.
2
Pump the brake pedal rapidly.
Builds up any remaining hydraulic fluid pressure in the master cylinder and wheel lines.
Three or four fast pumps can sometimes generate sufficient clamping pressure to regain partial stopping control.
3
Apply the parking brake with the release mechanism held.
Applies secondary mechanical braking force to the drive axle without locking wheels into an uncontrollable skid.
The parking system operates independently of service brake hydraulics but requires modulation to prevent jackknifing.
4
Steer into an open escape route.
Brings the vehicle to a full stop using road gradient, soft terrain, or open space away from hazards.
Dissipates remaining kinetic energy safely when primary stopping systems cannot bring the vehicle to a complete standstill on the roadway.

Key Concept

Standard sequential emergency response protocol for sudden commercial vehicle service brake loss.
Estimated Time:1m 15s
Rate this question

Topics

Brake Failure

More questions from this topic