Class 503

The Class 503 was a third rail DC (650v) electric multiple unit used on the Wirral and Mersey lines. The class was built in two batches, the first nineteen 3-car sets built in 1938 for the LMS (known as 1938 Stock) and a near identical second batch of twenty-four sets for British Railways in 1956-7 (1956 Stock) [1]. The Class 503s were advanced for their day with air-operated sliding doors and a high power to weight ratio thanks to the construction methods used which employed light alloys and avoided heavy frames [2].

28690 in LMS livery

Information
Number built:	129 cars (43 3-car sets)
Built:	1938, 1956-7
Builder:	Metro-Cammell / Birmingham Railway Carriage & Wagon Company
Engine:	4 BTH traction motors (650v DC third rail)
Power:	540 hp (403 kW)
Formation:	(Original) Driving Motor Brake Standard (DMBS)+Trailer Composite (TC)+Driving Trailer Standard (DTS) (Modified) DMBS+Trailer Standard (TS)+DTS

In the 1970s the stock was modified to have central end doors to comply with Department of Transport regulations for stock which operates in single track tunnels (to allow for the exiting of passengers in an emergency if the side doors cannot be used) [3]. They also had their first class provision removed to become fully standard class.

After a long career the Class 503 was finally withdrawn in 1985 and replaced by Classes 507 and 508. One set was retained and kept for special services until 1988, then it was preserved. The preserved set was from the 1938 Stock batch and is one of only two pre-war EMUs still in existence in close to original condition.

Another view of the preserved unit

[1] Colin J. Marsden, DMU and EMU Recognition Guide (Ian Allan, 2013) p, 381
[2] R.L. Vickers, EC Electric Trains and Locomotives in the British Isles (David & Charles, 1986) p. 74
[3] Brian Haresnape & Alec Swain, Third Rail DC Electric Multiple Units (Ian Allan, 1989) p. 28