British Rail Class 345

British Rail Class 345 Aventra
345002 after being delivered to Ilford E.M.U.D.
In service	May 2017
Manufacturer	Bombardier Transportation
Built at	Derby Litchurch Lane
Family name	Aventra
Constructed	2015–2018
Number under construction	66 trainsets
Formation	9 carriages per trainset
Fleet numbers	345001–345066
Capacity	450 seated, 4 wheelchair, 1500 people total
Operator(s)	Crossrail
Depot(s)	Old Oak Common
Line(s) served	Elizabeth Line
Specifications
Train length	205 metres (673 ft)
Doors	Plug, 6 sets of doors per carriage
Maximum speed	145 km/h (90 mph)
Weight	less than 350 tonnes
Acceleration	up to 1 m/s²
Electric system(s)	25 kV 50 Hz AC overhead lines conversion to 750 V DC third rail optional
Current collection method	Pantograph
Safety system(s)	CBTC (Crossrail Tunnels / Abbey Wood Branch) ERTMS (Great Western Main Line) AWS / TPWS (Great Eastern Main Line)
Coupling system	Dellner
Track gauge	1,435 mm (4 ft 8 1⁄2 in) standard gauge

The Class 345 is a Bombardier Aventra design electric multiple unit being manufactured for London's Crossrail. 66 nine-car trains are being manufactured at a cost of £1 billion, with each train able to reach 140 km/h (90 mph) and carry 1,500 passengers. The contract was awarded to Bombardier Transportation in February 2014 and the trains will enter service from May 2017. Initial deliveries are of seven-car sets, which will be extended to 9 car sets at a later date.

In 2008 the UK government's rolling stock plan stated a requirement for around 600 carriages for Crossrail, expected to be similar in design to the , to meet the design improvement requirements of the 2007 'Rail Technical Strategy' (RTS), including in-cab signalling/communication including satellite and ERTMS level 3 technologies, regenerative braking, low cost of operation and high reliability, with low weight and high acceleration.

The publicly released specifications included a passenger capacity of 1,500, with 450 seated, in a fully air-conditioned train no longer than 205 m (673 ft) with a top speed of 145 km/h (90 mph), and an energy efficiency as good as 24 kW·h per train-kilometre. Integration with platform screen doors is also expected. The capital value of the contract, which included construction of a depot at Old Oak Common, was estimated at around £1 billion, the total value may be greater due to the winning bidder expected to undertake maintenance of the trains for three decades, the estimated lifespan of the fleet.

The procurement programme was launched in December 2010. The package valued at approximately £1bn was for 60 high-capacity ten-carriage trains with a capacity of about 1,500 passengers and construction of maintenance depots.

In March 2011, Crossrail announced that Alstom, Bombardier, CAF, Hitachi and Siemens had been shortlisted. The initial bidding process was expected to start in late 2011, with a contract decision in 2013.