CDL General Knowledge TestCombination Vehicles (if applicable)Medium
During coupling, after backing the tractor under the trailer and before raising the landing gear, what is the next critical step to ensure a secure connection?
- AConnect the glad hands and electrical cable.
- BPerform a 'tug test' to check the fifth wheel connection.
- CRaise the landing gear completely.
- DCheck for proper height of the fifth wheel.
Show answer & explanationAnswer & explanation
Correct answer: B. Perform a 'tug test' to check the fifth wheel connection.
After backing under, locking the fifth wheel, and visually checking the connection, performing a 'tug test' is the next critical step. This physically verifies that the kingpin is securely locked into the fifth wheel before the trailer's full weight is transferred.
Why the other options are wrong
- A. Connecting air and electrical is important but comes after verifying the physical coupling.
- C. Raising the landing gear should only be done after the tug test confirms the connection is secure.
- D. Checking the fifth wheel height is done *before* backing under the trailer to ensure a proper angle.
Coupling: Tug Test
A procedure to physically verify the secure connection of the kingpin to the fifth wheel by gently pulling the tractor against the trailer's set brakes.
- Performed after locking jaws engage.
- Before raising landing gear.
- Confirms a safe coupling.
Memory trick: Lock, look, then tug, before you raise the landing rug.