Coupling can be tested by a driver:

Question

It is essential to safety that a driver inspects coupling before starting a trip. Trailer coupling on a double or triple combination can be tested by pulling against the pin of the second semi-trailer.

Accepted Answer

Pulling against the pin of the second semi-trailer.

Answer

Placing their fingers inside the coupling mechanism.

Answer

Placing glue over the fifth wheel.

Answer

Releasing the orange lever in the cab.