Skip to content

General Knowledge · Driving Emergencies

If a commercial vehicle's service brakes fail while driving, what should the driver do?

1.Downshift progressively for engine braking, press the parking brake or trailer hand valve steadily, and look at once for an escape routeCorrect answer
2.Shift into neutral and coast to a stop, since the vehicle will lose speed on its own once the throttle has been closed, with no braking at all
3.Pump the brake pedal rapidly and wait to see whether any air pressure comes back into the system on its own after a moment
4.Turn off the engine to force the vehicle to slow down more quickly than it otherwise would on a grade like that one

Explanation

The correct response to brake failure is to downshift progressively so the engine helps slow the vehicle, apply the parking brake or trailer hand valve with steady pressure, and immediately look for an escape route, such as a side street, open field, or runaway ramp. 49 CFR 383.111(a)(14)(iv) names brake failure as required knowledge without stating the procedure, so this is standard driver-training content, attributed to the manual. The wrong options each abandon a tool that is still available: coasting in neutral gives up engine braking entirely, pumping and waiting wastes the time needed to find an escape route, and shutting off the engine can lock the steering on many vehicles while doing nothing useful for stopping.

Source: 49 CFR 383.111(a)(14)(iv)

Drill Driving Emergencies questions

Related Driving Emergencies questions