A trailer has safety chains forming a secondary coupling beside the main coupling. What do they do if the main coupling separates?

Correct answer

Prevent the coupling bar from touching the ground if it becomes detached and allow a certain degree of control over the trailer to be retained.

They keep the coupling drawbar off the ground and allow some residual control of the trailer. They are not an electrical earth connection or an anti-theft system. Distinguish them from a device that automatically applies the trailer brake on separation. The General Vehicle Regulations require a secondary coupling on trailers with a maximum authorised mass of no more than 1,500 kg that lack a system ensuring braking if the coupling breaks. This does not permit driving with a faulty main coupling.