Crossrail has issued the first in a new series of updates on its progress to complete the delayed Elizabeth line.
Fit out of the tunnels is almost complete as the project moves on to the testing and commissioning phase for the trains and signalling systems.
Crossrail said it is still on target to meet the revised opening window between October 2020 and March 2021.
It added: “We will be able to provide increasing certainty about when the Elizabeth line will open once we start to fully test the operational railway and integrate the train and signalling software.
“Crossrail remains a hugely complex project, but pressures remain which the team is working hard to mitigate.
“The main areas of programme risk and uncertainty are currently contractor productivity, software testing for the train and signalling systems and systems integration.
“Crossrail Ltd is working closely with its Tier One contractors to demobilise their station delivery teams so that it can move ahead with integrating the nine new stations with the rest of the railway.”
Mark Wild, Chief Executive, Crossrail Ltd said: “Work to complete the Elizabeth line continues to make good progress against our new plan.
“Fit-out is nearing completion at many stations and testing of the train and signalling system is underway but there is still a huge amount to do before the central section can open.
“Crossrail is now in its critical and most challenging final phase due to the significant integration and testing work that remains to be completed.
“We are fully focused on completing the Elizabeth line and ensuring a safe and reliable passenger service as quickly as possible.”