Companies bidding for the main tunnelling contracts on the UK's £16bn ($24bn) Crossrail project will be asked to include two new stations in their bids in an effort to lower costs.
Construction at Liverpool Street and Whitechapel, and Bond Street and Tottenham Court Road has already been combined, giving the bidders an option to include either the western or eastern stations when they submit their bids in the summer.
The western tunnel will be bored from Royal Oak through to the new Farringdon station and the eastern tunnel will be bored from Stepney Green through to Pudding Mill Lane, and Limmo Peninsula through to Victoria Dock to the east.
The station tunnels work is scheduled to finish in 47 months and will include building platforms, concourses, cross passages and escalator tunnels, according to building.co.uk.
The bidders for the tunnelling works include joint ventures from Balfour Beatty, Morgan Est and Vinci, Bam Nuttall, Ferrovial Agroman and Kier, Costain, Skanska and Bilfinger Berger Civil, Dragados and John Sisk & Son, and Laing O'Rourke and Bouygues.
Crossrail is expected to open in 2017.