Dual coupling

The screw coupling is mounted on a hinge on the opposite side of the knuckle coupler.

Exceptions are the new LHB coaches imported from Europe, and a few other makes of carriages converted to use knuckle couplers.

British locomotive-hauled passenger carriages adopted a dual coupling system in the 1950s.

They have retractable buffers and a central Buckeye automatic knuckle coupler that lowers to reveal a hook for a screw-type chain coupling.

Today this dual coupling system has been adopted for all loco-hauled passenger trains in Great Britain to allow faster shunting operations.

Combined Janney and Shibata couplers on a JNR Class EF63 locomotive (left) connected to a 115 series EMU (right). The dual couplers are mounted to a pivot, allowing both to swing.