Crossrail chiefs insisted on Tuesday that the long-awaited line remained on course to open by the end of June.
Mass evacuation test events – which will involve thousands of volunteers role-playing to test the emergency response – are due to be held at the over the coming weekends.
Transport for London said “significant progress” was made over Christmas and the “trial operations” phase, which began on November 20, saw upgrades to train and signalling software and tunnel fire safety schemes.
A precise opening date has yet to be announced but TfL commissioner Andy Byford said he would not allow the line – which will be renamed the Elizabeth line when services start running – to open until he was sure it was reliable.
Originally due to have been opened by the Queen in December 2018, Crossrail has gone billions over budget, with the total cost now in excess of £20 billion.
Last week it emerged that the impact of the pandemic is expected to cost it about £1 billion in lost fares in its first three years, due to the increase in commuters working from home and fewer visitors to central London.
The trial operations phase, which involves running 12 trains an hour between Paddington and Abbey Wood, is about 40 per cent complete.
Eight of the 10 new stations are complete, with Canary Wharf station due to be handed over in a matter of weeks. However, Bond Street station is around three months behind schedule.
Mayor Sadiq Khan said: “The Elizabeth line will transform travel across London and the South East. I’m delighted it is on track to open in the first half of 2022, in what will be a landmark moment for the capital.”
Crossrail will initially open in three sections – the central section between Paddington and Abbey Wood, alongside the above-ground sections already running as TfL Rail – the services between Shenfield and Liverpool Street in the east, and between Reading, Heathrow and Paddington in the west.
Services from Reading, Heathrow and Shenfield will connect with the central tunnels from autumn 2022, with full end-to-end running in place by May 2023.
Mr Byford said: “This is an extremely exciting year for us and for London as we get ever closer to opening the Elizabeth line and welcoming customers from Abbey Wood to Paddington.
“The launch of this much needed and transformational addition to the transport network will be central to the recovery for London and the UK. There will be no better symbol of London’s renaissance from the pandemic.”