 Those carriages were withdrawn and refitted with electric lighting and control cables for motor communication.The conversions did not happen immediately, but by 1921 1st class trailers 1AT-12AT and 14AT-18AT, and conversion work was progressing for the fleet of second class trailers 1BT through (roughly) 100BT.In 1921 it was decided that having class segregation among each class of the suburban fleet was too difficult to manage appropriately, and so the trailers all became first class and the motors all second class.