Crossrail has been delayed again until 2021 with costs rising by up to £650m, TfL have announced, with software development for the signalling and train systems, and the complex assurance and handover process for the railway cited as the two critical reasons for the latest delay.

The complex project had initially been expected to open in December 2018, but has been plagued by delays and spiralling costs, and a National Audit Office report in May this year found that a fixation on the opening date had “adversely influenced decisions.” 

In April, Crossrail outlined its new plan to complete the outstanding works with an expected delivery window between October 2020 and March 2021 for the start of Elizabeth line services through central London.

Crossrail now say the Elizabeth line will open as soon as practically possible in 2021, with a more comprehensive update on progress expected early in 2020.

The latest projections now show a central cost forecast (including risk contingency) of almost £16bn (£15,363m), which is £400m more than envisaged. Further modelling scenarios consider even higher levels of risk of £650m more than the funding already committed under a DfT finance package.

Mark Wild, chief executive of Crossrail Ltd, said: “The two critical paths for the project remain software development for the signalling and train systems, and the complex assurance and handover process for the railway; both involve safety certification for the Elizabeth line. These must be done to the highest quality standards to ensure reliability of the railway from day one of passenger service.

“Crossrail Ltd will need further time to complete software development for the signalling and train systems and the safety approvals process for the railway. Our latest assessment is that the opening of the central section will not occur in 2020, which was the first part of our previously declared opening window. 

“The Elizabeth line will open as soon as practically possible in 2021. We will provide Londoners with further certainty about when the Elizabeth line will open early in 2020.

"Our detailed cost forecasts continue to show that the project’s costs will increase due to programme risks and uncertainties. The latest projections indicate a range of between £400m to £650m more than the revised funding agreed by the mayor, government and Transport for London in December 2018.

“We are doing everything we can to complete the Elizabeth line as quickly as we can but there are no short-cuts to delivering this hugely complex railway. The Elizabeth line must be completed to the highest safety and quality standards.”

The latest delay was announced six months after the London assembly called on Crossrail’s new management team to be “realistic, pragmatic and honest with themselves and Londoners”, and to “leave behind the days of chasing an opening date and focus on the successful delivery of a new line for Londoners.”