CDL Combination Vehicles TestCombination Vehicle Air BrakesMedium
A driver is preparing to couple a tractor to a semi-trailer. After backing the tractor under the trailer, raising the landing gear slightly, and connecting the air lines and electrical cable, what is the next critical step to ensure a secure connection before fully raising the landing gear?
- AInspect the kingpin for damage.
- BCheck for proper fifth wheel lubrication.
- CMake sure the glad hands are sealed correctly.
- DPull gently forward against the trailer to check the connection.
Show answer & explanationAnswer & explanation
Correct answer: D. Pull gently forward against the trailer to check the connection.
After connecting the lines and slightly raising the landing gear, gently pulling forward against the trailer is essential to confirm that the kingpin is securely locked into the fifth wheel. This prevents the trailer from separating from the tractor during operation.
Why the other options are wrong
- A. Kingpin inspection for damage should be done before backing under the trailer, as part of the initial trailer inspection.
- B. Fifth wheel lubrication is important but should be checked earlier in the pre-coupling process, not as the next step after connecting lines.
- C. Ensuring glad hands are sealed is done when connecting the air lines, which occurs prior to this specific next step.
Coupling Check (Pull Test)
After connecting air/electrical lines and slightly raising landing gear, gently pull the tractor forward against the trailer to confirm the kingpin is locked.
- Verifies secure fifth wheel connection
- Prevents trailer separation
- Done before fully raising landing gear
Memory trick: Connect, lift, pull, then you're ready to roll!