There will be new stations at Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool Street and Whitechapel, with interchanges with the London Underground and other National Rail services.
One branch runs to Heathrow Central (for Terminals 2 and 3), Heathrow Terminal 4 and Heathrow Terminal 5, The main western section runs on the surface from Reading to Acton Main Line.
Construction of a flyover near Hayes & Harlington station began in 2014, and will allow Heathrow Express trains to pass over the track used by Crossrail, avoiding delays caused by crossings.
The central tunnels run from a portal just west of Paddington to Whitechapel, with further tunnelling to Stratford and to Canary Wharf.
An almost entirely new line will branch from the main line at Whitechapel to Canary Wharf, crossing under the River Thames, with a new station at Woolwich and finally connecting with the North Kent Line at the Abbey Wood terminus.
Crossrail will be operated by MTR Corporation (Crossrail) Ltd as a London Rail concession of Transport for London, in a similar manner to London Overground.