A report by Parliament’s Public Accounts Committee (PAC) has warned that the final bill for the already over-budget Crossrail project cannot be foreseen.

In a report into the project the committee of MPs said that given the scale and complexity of the remaining work to get the railway open, it was “staggering” that they were still projecting to open in December 2018 as late as July 2018.

The previous Chair and Chief Executive still assert that sticking to the December 2018 opening date was important to keep contractors motivated and costs low, and they continue to emphasise that they had overcome significant engineering challenges at earlier stages in the programme.

Part of the problem has been laid at the decision to split the project into 36 separate smaller construction contracts, rather than fewer larger contracts. Your correspondent recalls one site visit that required three separate safety briefings due to moving between three contractor controlled areas.

The former Chair placed some blame for performance falling behind schedule at the feet of some of the key contractors who had been “causing problems”, but the Committee notes that it was Crossrail’s job to manage its contractors, and failed to understand the extent to which contractors’ levels of productivity were diverging significantly and repeatedly from its expectations.

Although Crossrail management at the time come under heavy fire, so does the Department for Transport for their lack of oversight on a project which absorbed such a high upfront package of taxpayer funding. The DfT has acknowledged that striking a balance between autonomy and oversight of its delivery bodies is one of its main lessons from Crossrail.

Crossrail currently estimates that the central section of the railway will open between October 2020 and March 2021, a delay of around two years. The full line, with all the trimmings probably wont be ready until 2022.

In a separate statement from the DfT, they have confirmed that they are still on target to launch TfL Rail branded services between Paddington and Reading by the end of this year.

However, trains are unlikely to stop at Bond Street for at least another year after that. There is also substantial work to complete at at least eight stations on the existing network to the east and west of London, including Ealing Broadway, Acton Main Line, Romford and Ilford, and there is a risk that not all of the stations will have step-free access when the Elizabeth line eventually opens.

The running costs of the railway will also be higher than anticipated at first, as delays to installing some of the systems will mean more staff need to be employed to run the network.

The biggest issue in the report though is that the Committee says that it still cannot be sure that the £17.6 billion cost of Crossrail wont rise even further over the next year.