SR Class 3-SUB

For the London, Brighton and South Coast Railway AC electric multiple units, see SR Class CP, SR Class CW, and SR Class SL.

Southern Railway 3-SUB Units
South Eastern division electric multiple units sandwich a trailer set. Orpington, 1928
In service	1915-48
Formation	power car + trailer car + power car
Operators	London and South Western Railway, Southern Railway and British Railways (Southern Region).
Specifications
Maximum speed	75 mph (121 km/h)
Prime movers	Early units: 4 x 275 hp (205 kW) traction motors total 1,100 hp (820 kW) Later units: 4 x 250 hp (190 kW) traction motors total 1,000 hp (750 kW)
Braking system	Air (Westinghouse)
Track gauge	4 ft 8+1⁄2 in (1,435 mm)

The SR Class 3-SUB were DC suburban electric multiple units, introduced by the London and South Western Railway in 1915. They were constructed by the Southern Railway in the period up to 1939, and though the class designation 3-SUB was not used by the Southern Railway, some authors refer to these units as 3-SUB. When rebuilt to four cars in the 1940s, they became class 4-SUB.