If the dolly has air brakes, how are they released?

Air brakes on a dolly are essential for safe operation, and understanding how to release them is crucial for proper handling of doubles and triples trailers. When the air tank petcock is opened, it allows the compressed air from the air tanks to flow into the brake system, thereby releasing the brakes. This action ensures that the system can equalize pressure and that the brakes are no longer applied, allowing for the safe movement of the dolly.

Opening the air tank petcock is the correct procedure because it directly facilitates the release of air pressure that keeps the brakes engaged. This is particularly important in ensuring that the vehicle can be maneuvered safely after stopping or parking. Understanding the mechanics of the air brake system and how to operate it properly is vital for any driver with a doubles or triples endorsement to ensure safety on the road.