CDL Vehicle Combination Practice Test

To ensure the fifth wheel is properly locked when coupling a trailer, it's important to perform a visual check along with applying the trailer brakes. This combination of actions allows the driver to confirm both the physical connection of the trailer to the truck and that the coupling mechanism has engaged securely.

A visual inspection lets you see if the fifth wheel jaws have closed around the kingpin of the trailer and that there are no visible issues, such as misalignment or improper seating. Applying the trailer brakes afterward helps to verify that the trailer is indeed locked in place. If the brakes engage properly, it confirms that the connection is secure and the fifth wheel is locked.

Ensuring the proper locking of the fifth wheel is critical for safe operation on the road, as any failure in this connection could lead to dangerous situations, such as the trailer coming loose during transit. Other methods, such as relying solely on the trailer brakes or only conducting a visual check, do not provide the necessary level of assurance that the trailer is securely coupled. Checking the weight of the trailer is not relevant for confirming the lock and does not contribute to the proper coupling process.