A commercial vehicle driver traveling on a multi-lane expressway encounters a sudden traffic slowdown and discovers that excessive pushrod travel combined with overheating has caused total service brake fade. Having already completed sequential downshifting to maximize engine braking, which action should the driver execute to bring the vehicle to a controlled stop?
- Apply the parking brake control cautiously, releasing or modulating it immediately if the drive wheels lock up to prevent a severe skid.Answer
- BPull the parking brake valve fully into the locked position and hold it locked to maximize tire friction against the pavement surface.
- CShift the transmission into neutral and steer toward the paved shoulder to allow rolling resistance alone to stop the vehicle.
- DEngage an auxiliary retarder at its maximum setting while steering onto an unpaved median to scrub speed.
Answer
Apply the parking brake control cautiously, releasing or modulating it immediately if the drive wheels lock up to prevent a severe skid.
When service brakes fail completely and downshifting has already been utilized, the parking or emergency brake can be applied to stop the vehicle. However, because the parking brake applies full mechanical spring pressure directly to the wheels, it must be carefully modulated—or released if wheels begin to lock—to prevent an uncontrollable skid or jackknife.
Step-by-Step Solution
Key Concept
Emergency stopping procedures and parking brake modulation during service brake failure
Estimated Time:1m 30s