CDL Air Brakes TestUsing Air BrakesMedium
A driver needs to park a commercial vehicle equipped with air brakes on a slight downgrade. In addition to engaging the parking brake, what other essential safety measure should be taken?
- ALeave the transmission in neutral.
- BDrain all air from the air tanks.
- CEngage the emergency brake and leave the service brakes applied.
- DChock the wheels.
Show answer & explanationAnswer & explanation
Correct answer: D. Chock the wheels.
When parking on a downgrade, especially with a heavy vehicle, chocking the wheels is an essential additional safety measure, even with the parking brake engaged. This provides a physical barrier against rolling if the parking brake were to fail or slowly leak pressure.
Why the other options are wrong
- A. Leaving the transmission in neutral removes any engine braking assistance and is not a safe practice on a downgrade.
- B. Draining all air from the tanks would indeed apply the spring brakes, but it's not the primary additional safety measure for a downgrade, and the tanks should not be fully drained except for maintenance.
- C. The emergency brake IS the parking brake in an air brake system. Leaving the service brakes applied would drain air pressure from the system, potentially releasing them over time.
Parking on Downgrade (Air Brakes)
The procedure for safely securing a commercial vehicle with air brakes on a sloped surface, requiring the use of the parking brake and additional wheel chocks.
- Engage parking brake.
- Chock the wheels.
- Prevents accidental rolling.
- Crucial safety measure on grades.
Memory trick: On a grade, don't just brake, add chocks for safety's sake.