After the jaws lock when coupling, you should:

The correct approach after the jaws lock when coupling is to perform a tug test followed by a visual confirmation of the coupling's security. This procedure is vital for ensuring that the trailer is securely attached to the tractor.

The tug test involves gently pulling forward to check if the trailer is properly secured and that the jaws have indeed locked around the kingpin. If the trailer moves and comes uncoupled during this test, it indicates that the connection was not secure, which could lead to dangerous situations when driving.

Visually confirming the coupling helps in identifying any visible issues, such as misalignment or incomplete attachment. This thorough check ensures that both mechanical and visual safety measures are adhered to before operating the vehicle.

The other options lack essential safety measures. For instance, inspecting lights and driving away does not address the stability of the coupling. Relying on a fellow driver could lead to miscommunications or oversights. Raising the landing gear before confirming the coupling can risk the trailer being disconnected if it is not secure, thus jeopardizing safety during travel.