Crossrail 2 funding problems could be solved by building the line in stages, managing director Michele Dix said.
The scheme, which would be an underground line from Wimbledon in south-west London to Tottenham Hale in the north-east, with regional branches to Broxbourne, Epsom, Shepperton and Chessington, will cost £31bn to build.
Dix told the New Civil Engineer Tunnelling Summit 2017 that building and opening the line in “chunks” has been considered as a solution to the gap in funding. The options are either phase building, where each section of the line is a separate entity as with HS2, or stage building, where it is one project that is built in sections.
She said: “We have got to make the scheme more affordable…[and consider] whether or not the scheme could be built in chunks, will that make it more affordable?”
However she added that there is a risk with building in phases as some parts may not get built, saying “it has to stack up all by itself if the second part never comes”.
There is demand for housing at the north-east of the proposed route, a need to ease congestion on the rail line in the south west, and pressure to relieve overcrowding at central London underground stations, which means choosing which sections to build first would be a challenge, Dix added.
The project must be more affordable so that “Crossrail 2 can go ahead but so can other schemes important to the UK such as Northern Powerhouse Rail and the Midlands Engine”, she said.
Transport secretary Chris Grayling confirmed his support for the project in July this year, but said London would need to cover half of the bill during construction. The desired opening date for the line is the 2030s, to coincide with the completion of HS2 Phase 2b, which is expected to cause overcrowding at Euston underground station if Crossrail 2 is not built.
Speaking at the launch of the Transport Infrastrucutre Efficiency Strategy yesterday, Grayling said that he wanted both Northern Powerhouse Rail - the proposed line from Liverpool to Hull - to be built as well as Crossrail 2.