Which of the following is true regarding the dolly parking brake?

The dolly parking brake is crucial for securing the dolly, especially when it is uncoupled from the tractor. When dealing with a dolly in a double or triple trailer setup, the parking brake helps to prevent the dolly from rolling away. This security measure is important for both safety and stability in the overall configuration of the trailers.

Additionally, using the dolly parking brake ensures that the trailers remain in place while loading or unloading, reducing the risk of accidents. Proper engagement of the parking brake is part of standard operating procedures for truck drivers, especially when dealing with multiple trailers. It serves as a foundational safety feature in the operation of dolly and trailer setups.