Sofia Metro opened bids for the contract on August 13, revealing that the consortium had offered a price of Levs 418m ($US 238.6m), while its rival CAF had submitted a bid of Levs 483m.
Siemens and Newag are offering a 60m-long version of Siemens' Inspiro metro train which the consortium has already supplied to Warsaw.
The 7km central section of Line 3 from Botevgradsko Shosse to Ovcha Kuptel will run entirely underground in a double-track bored tunnel and will have seven stations. When all phases are complete, the line will run for 16.5km from Vassil Levski in the east to Knazyhevo in the west, interchanging with Line 1 at St Clement and Line 2 at NDK.
Peak ridership is forecast to be 6500 passengers per hour per direction (pphpd) and the line will have design capacity to accommodate 13000 pphpd with trains running at 90-second headways.
Trains will be 60m long and platforms will be 100m long to accommodate future train lengthening if required.
Unlike lines 1 and 2, which are equipped with third-rail electrification, traction power will be provided by 1.5kV dc overhead electrification.
The project is being partially funded by the European Union through the 2014-2020 Operational Programme Transport for Bulgaria.