When testing the air service brakes, what is the recommended action?

When testing the air service brakes, the recommended action is to brake firmly while slowly moving forward. This method allows the driver to effectively assess the response of the braking system under actual driving conditions, helping to check for proper function and feel of the brakes. During this testing process, a firm application of the brakes is necessary to gauge their effectiveness, ensuring that they engage properly and bring the vehicle to a controlled stop without any delay or unusual behavior.

Soft braking while moving forward might not provide a clear indication of how well the brakes are functioning, as a lack of sufficient pressure can mask any issues. Braking sharply while stationary does not simulate real driving conditions and may not reveal potential problems with the braking system. Meanwhile, braking while reversing can be misleading and potentially unsafe, as it does not account for the dynamics involved when a vehicle is moving forward.