If the vehicle is designed to accept other devices which do not enable the straps to be directly attached to belt anchorages without intervening sheaves or other similar devices or which require belt anchorages supplementary to those mentioned in point 4.3, the safety belt or an arrangement of wires, sheaves or other similar devices representing the equipment of the safety belt, shall be attached by such a device to the belt anchorages in the vehicle and the belt anchorages shall be subjected to the tests prescribed in point 5.4, as appropriate.