Emergency Procedures & Safety Protocols Flashcards
6 cards from real Air Brake Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Emergency Procedures & Safety Protocols flashcards as text
When air pressure drops to approximately 20–45 psi in a vehicle with spring brakes, what happens?
Answer: The spring brakes automatically apply, bringing the vehicle to a stop
Spring brakes are held off by air pressure; when pressure falls to approximately 20–45 psi, the springs overcome the air and apply the brakes automatically as a fail-safe measure.
What should you do if your air pressure warning light comes on while driving?
Answer: Safely pull off the road immediately and stop before pressure drops to the point where spring brakes apply
The warning light activates at about 60 psi; you must stop safely before pressure drops further and the spring brakes apply automatically, which could cause a sudden and uncontrolled stop.
What is a 'brake fade' and how does it affect stopping distance during an emergency?
Answer: Reduced braking effectiveness due to heat, which significantly increases stopping distance
Brake fade occurs when friction surfaces overheat, reducing their ability to generate stopping force, which greatly increases stopping distance — especially dangerous in an emergency.
In an emergency where the trailer begins to jackknife, what is the correct immediate action?
Answer: Release the brakes to allow the trailer wheels to regain traction and straighten
Releasing brake pressure allows the locked trailer wheels to roll again, restoring traction and allowing the trailer to straighten. Continued braking sustains the jackknife.
What is the role of the trailer breakaway valve in an emergency separation?
Answer: It automatically applies the trailer brakes if the trailer becomes disconnected from the tractor
The breakaway valve uses a pull cord connected to the tractor; if the trailer separates, the cord pulls the valve, cutting off air to the trailer service line and applying the trailer spring brakes.
Why should a driver never attempt to 'fan' the brakes (rapidly pumping) on a vehicle equipped with air brakes during an emergency stop?
Answer: Repeatedly pumping depletes the air supply faster, potentially causing complete brake failure before stopping
Each brake application uses air; rapid repeated pumping in an emergency rapidly depletes tank pressure, potentially draining enough air to cause spring brake application before the vehicle can be stopped safely.