CDL Vehicle Combination Practice Test

After locking the kingpin into the fifth wheel, how should you check the connection?

1. Pulling the tractor ahead gently with trailer brakes locked

2. Visually inspect the connection

3. Ask a partner to check

4. Rely on the sound of the lock

The correct answer is: Pulling the tractor ahead gently with trailer brakes locked

The correct method for checking the connection after locking the kingpin into the fifth wheel is by pulling the tractor ahead gently with the trailer brakes locked. This maneuver ensures that the connection is secure and that the kingpin and the fifth wheel are engaged properly. When the tractor pulls forward, it puts pressure on the fifth wheel, confirming that the kingpin is locked in place and cannot disconnect. This method effectively demonstrates the operational integrity of the hitching mechanism under realistic conditions. While visually inspecting the connection is important in the initial inspection process, it does not provide the assurance that comes from actual movement. A visual check alone may miss subtle issues that could arise during operation. Relying on a partner to check can introduce additional variables and is not always feasible or safe, especially in a solo operation. Similarly, while the sound of the lock engaging can provide some reassurance during the hookup, it is not a definitive test of the connection's integrity under load. Therefore, the act of gently pulling the tractor forward with the brakes engaged is the most reliable method to confirm that the hitch is properly connected.