The latest addition to the underground network, which will be known as the Elizabeth Line once opened, had been due for completion this December.
However, Crossrail Limited has said that more time is needed to complete “final infrastructure and extensive testing” to ensure a “safe and reliable railway” is delivered for customers “from day one of passenger service”.
Services are already running on part of the line, temporarily dubbed TFL Rail, but the central section between Paddington and Abbey Wood will now not open until autumn 2019.
The construction of the project is drawing to a close with the completion of the remaining mechanical, electrical and communications systems along with architectural fit-out in the new central section stations.
The remaining rail infrastructure works are due to be completed this year. This ranges from removal of temporary services to completing the remaining installation of the permanent lighting and drainage pumps in the tunnels.
Simon Wright, Crossrail Chief Executive, said: “The Elizabeth line is one of the most complex and challenging infrastructure projects ever undertaken in the UK and is now in its final stages.
“We have made huge progress with the delivery of this incredible project but we need further time to complete the testing of the new railway.
“We are working around the clock with our supply chain and Transport for London to complete and commission the Elizabeth line.”
The original programme for testing is said to have been compressed by more time being needed by contractors to complete fit-out activity in the tunnels and the development of railway systems software.
Railway systems cover the integrated systems and associated software that required to operate the railway including rolling stock, signalling, tunnel ventilation, communications and power.
When it is fully opened, trains will run from Reading and Heathrow in the west through 13 miles of new tunnels to Shenfield and Abbey Wood in the east.
