British Rail Class 399

British Rail Class 399 Citylink
Class 399 at Parkgate in April 2019
In service	14 September 2017 (2017-09-14)–present
Manufacturer	Vossloh España
Built at	Valencia, Spain
Family name	Citylink
Constructed	2014–2015
Number built	7
Fleet numbers	399201–399207
Capacity	236 (96 seated, 140 standing)
Operators	Sheffield Supertram
Depots	Nunnery (Sheffield)
Lines served	Supertram network, Dearne Valley line
Specifications
Car body construction	Stainless steel
Train length	37.200 m (122 ft 0.6 in)
Width	2.650 m (8 ft 8.3 in)
Height	3.720 m (12 ft 2.5 in)
Floor height	425 mm (1 ft 4.7 in) at doors
Doors	Double-leaf sliding plug, 2 per side per end section
Articulated sections	3
Wheel diameter	720 mm (28 in)
Maximum speed	62 mph (100 km/h)
Weight	Approx. 66 t (65 LT; 73 ST)
Steep gradient	10%
Traction system	ABB IGBT-VVVF[1]
Traction motors	6 × 145 kW (194 hp)
Power output	870 kW (1,170 hp)
Acceleration	1.15 m/s2 (2.6 mph/s)
Deceleration	Service: 1.2 m/s2 (2.7 mph/s) Emergency: 2.67 m/s2 (6.0 mph/s)
Electric system(s)	750 V DC and 25 kV 50 Hz AC overhead line
Current collector(s)	Pantograph
UIC classification	Bo′+2′Bo′+Bo′
Minimum turning radius	Horizontal: 22 m (72 ft 2 in) Vertical: 165 m (541 ft 4 in)
Safety system(s)	AWS TPWS
Track gauge	1,435 mm (4 ft 8+1⁄2 in) standard gauge
Notes/references
Sourced from [2][3] unless otherwise noted.

The British Rail Class 399 Citylink is a type of rail vehicle built by Vossloh on its Citylink platform for operation by Sheffield Supertram. Primarily a low-floor tram, it is also capable of being used on the National Rail network; the Class 399 is the first such tram-train to see operational use in the United Kingdom.

In 2013, an order was placed with Vossloh for the construction of a batch of seven tram-trains for Supertram. It operates as a pioneering tram-train hybrid vehicle as part of an initial pilot of the operation of such vehicles.^[4] The launch of live services using the Class 399 was repeatedly delayed, reportedly due to planning and development-related difficulty experienced by Network Rail, who were responsible for the installation of additional track and other infrastructure-related changes to accommodate the tram-trains upon the heavy rail network, as well as a necessary full track replacement programme performed by Supertram.

In January 2016, the first tram-train commenced live testing on the Supertram network. The type first entered passenger service on 14 September 2017, but were initially restricted to only some sections of Supertram's network as further work was still required on other parts, including Network Rail lines. Full tram-train service began on 25 October 2018. The results of the trials may become a decisive factor on the adoption of tram-train technology at various other sites across the country.