British Rail Class 312

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British Rail Class 312
First Great Eastern Class 312 at Kirby Cross in 2004
Inside a Class 312 unit before refurbishment
In service	1975–2004
Manufacturer	British Rail Engineering Limited
Order no.	30863 (312/0 BDTSOL vehicles) 30864 (312/0 MBSOs) 30865 (312/0 & /1 TSOs) 30866 (312/0 DTCOLs) 30867 (312/1 BDTSOLs) 30868 (312/1 MBSOs) 30870 (312/1 DTCOLs) 30891 (312/2 BDTSOLs) 30892 (312/2 MBSOs) 30893 (312/2 TSOs) 30894 (312/2 DTCOLs)[1]
Built at	Holgate Road, York
Family name	BR First Generation (Mark 2)
Replaced	Class 125
Constructed	1975–1978
Number built	49
Number preserved	0 (2 vehicles from 1 unit)
Successor	Class 317 Class 321/4 Class 323 Class 360
Formation	4 cars per unit: BDTSOL-MBSO-TSO-DTCOL
Diagram	ED212 (312/0 MBSOs) ED213 (312/1 MBSOs) ED214 (312/2 MBSOs) EE305 (all DTCOLs) EF213 (all BDTSOLs) EH209 (all TSOs)[1][2]
Fleet numbers	As built: 312/0: 312001–312026 312/1: 312101–312119 312/2: 312201–312204 As rebuilt: 312/0: 312701–312726 312/1: 312781–312799 312/2: 312727–312730[3]
Capacity	As built: 322 seats (25 first-class, 297 standard)[2]
Operators	British Rail c2c Central Trains First Great Eastern
Depots	Bletchley Clacton Hornsey[4]
Specifications
Car body construction	Steel[2]
Train length	256 ft 8+1⁄2 in (78.245 m)[3]
Car length	Drv. cars: 65 ft 1+5⁄8 in (19.853 m) Int. cars: 65 ft 4+1⁄4 in (19.920 m)[2]
Width	9 ft 3 in (2.82 m)[2]
Height	12 ft 4+1⁄2 in (3.772 m)[2]
Floor height	3 ft 9 in (1.14 m)[2]
Doors	Hinged, manually operated ("slam")[3]
Wheelbase	Motor bogies: 9 ft 0 in (2.74 m) Trailer bogies: 8 ft 6 in (2.59 m) Over bogie centres: 46 ft 6 in (14.17 m)[2]
Maximum speed	312/0 & /1: 90 mph (140 km/h) 312/2: 75 mph (121 km/h)[2]
Weight	BDTSOL: 35 tonnes (34 long tons; 39 short tons) DTCOL: 33 tonnes (32 long tons; 36 short tons) 312/0 MBSO: 56 tonnes (55 long tons; 62 short tons) 312/1 &/2 MBSO: 55.5 tonnes (54.6 long tons; 61.2 short tons) TSO: 30.5 tonnes (30.0 long tons; 33.6 short tons)[2]
Traction motors	4 × English Electric 546A[4][5]
Power output	1,080 hp (810 kW)[3]
HVAC	Electric heating[2]
Electric system(s)	6.25 kV 50 Hz AC overhead (312/1s only) 25 kV 50 Hz AC overhead (all)[3]
Current collector(s)	Pantograph
UIC classification	2′2′+Bo′Bo′+2′2′+2′2′
Bogies	Motor cars: BREL BP14 Trailer cars: BREL BT8[2]
Minimum turning radius	231 ft 0 in (70.41 m)[2]
Braking system(s)	Electro-pneumatic[2]
Safety system(s)	AWS[2]
Coupling system	Drop-head buckeye[6]
Multiple working	Within class, and with Class 310
Seating	Transverse
Track gauge	1,435 mm (4 ft 8+1⁄2 in) standard gauge

The British Rail Class 312 alternating current (AC) electric multiple units (EMUs) were built between 1975 and 1978^[7] for use on outer-suburban passenger services. It was the last class of multiple unit to be constructed with the British Rail Mark 2 bodyshell, as well as the last class of multiple unit to be built with slam doors in Britain. These features contributed to their relatively early withdrawal at 25–28 years old, compared with a typical EMU life expectancy of 30–40 years.