CDL Vehicle Combination Practice Test

Before backing under a trailer, confirming that the trailer brakes are locked is crucial for safety and operational efficiency. When the trailer brakes are set, it ensures that the trailer remains stationary and doesn't roll away during the coupling process. This prevents dangerous situations, such as the trailer moving unexpectedly while the truck is trying to line up for the connection, which could lead to accidents or damage to both the truck and the trailer.

Properly locking the trailer brakes not only aids in maintaining control during the backing process but also ensures that the coupling can be done without additional complications. This step is fundamentally significant to secure the load and ensure a smooth and safe operation.

Assessing the compatibility of the hitch, checking for sufficient clearance, and ensuring tire inflation are all important aspects of vehicle safety and operation but are secondary to the immediate necessity of ensuring the trailer is stable before attempting to couple or back under it.