Road shuttle in 1918. From 1925 to 1934 these vehicles were used between Watford and Rickmansworth. In 1913, an order was placed for 23 motor cars and 20 trailers, saloon cars with sliding doors at the end and the middle. These started work on circle services, including the new electric service to New Cross via the East London line. In 1921, 20 motor cars, 33 trailers and 6 first-class driving trailers were received with three pairs of double sliding doors on each side. These were introduced on circle services. Between 1927 and 1933 multiple unit compartment stock was built in batches by the Metropolitan Carriage & Wagon and Birmingham Railway Carriage & Wagon Company companies to be used on electric services from Baker Street and the City to Watford and Rickmansworth. The first order was only for motor cars; half had Westinghouse brakes, Metropolitan-Vickers control systems and four MV153 motors; they replaced the motor cars working with bogie stock trailers. The rest of the motor cars had the same motor equipment but used vacuum brakes, and worked with converted 1920/23 Dreadnought carriages to form 'MV' units. In 1929, 'MW' stock was ordered, 30 motor coaches and 25 trailers similar to the 'MV' units, but with Westinghouse brakes. A further batch of 'MW' stock was ordered in 1931, this time from the Birmingham Railway Carriage & Wagon Co. This was to make seven 8-coach trains, and included additional trailers to increase the length of the previous 'MW' batch trains to 8 coaches. These had GEC WT545 motors, and although designed to work in multiple with the MV153, this did not work well in practice. London Passenger Transport Board In 1933, the Metropolitan and District railways were merged with the other underground railways, tramway companies and bus operators to form the London Passenger Transport Board (LTPB). In 1934, ninety former Metropolitan Railway cars were refurbished to form the Circle Stock. Although most of these cars were made in 1921, some were older. The motors were replaced and the cars were repainted a red and cream. Serving the Metropolitan main line there were three incompatible types of multiple unit compartment stock that had been built in 1927–33, and these were assembled into 9 × 8-car and 10 × 6-car trains after Westinghouse brakes were fitted and some cars regeared. The LPTB, continuing the District Railway multiple unt classification system labelled these T Stock.