What step should be taken after raising and securing the landing gear?

After raising and securing the landing gear, the appropriate step is to supply air to the trailer and test the service brake. This action is crucial because it ensures that the brakes are functioning properly before the trailer is put into operation. Testing the service brake confirms that the air brake system is fully engaged and that there are no leaks or malfunctions. It is an important safety measure, as effective brakes are essential for controlling the vehicle and ensuring safe transport.

While other actions, such as disconnecting electrical connections or checking fuel levels, may be part of the pre-trip or post-trip procedures, they do not directly follow the securing of the landing gear in terms of preparing the trailer for movement. Ensuring that the braking system is operational offers immediate feedback regarding the trailer's readiness for road safety and compliance with regulations.