 The following month, after four of the carriages had been converted into motor cars and fitted with British Thomson-Houston control equipment that had been invented by Frank J. Sprague in Chicago, an electric multiple unit was tested.The report, published February 1902, found that the multiple unit was superior, and in May 1902 the CLR ordered 64 motor cars, 40 from Birmingham Railway Carriage and Wagon and 24 from Metropolitan Amalgamated Railway Carriage & Wagon.Seating 42 passengers, 24 in transverse bays and 18 on longitudinal seating, these were powered by two GE66 traction motors.