Network Rail carried out upgrades to the existing tracks and stations in west London during the Spring Bank Holiday as part of the Crossrail programme .
Three quarters of the new railway's route, which will be known as the Elizabeth Line from December 2018, runs above ground through outer London, Berkshire and Essex.
Network Rial have been working to upgrade the infrastructure so it can cope, including platform extensions and upgrades at Hayes & Harlington, Southall and West Ealing.
As well as these changes, construction on the flyover at Stockley junction continued, which will form the basis of a new ramp.
Network Rail hope that the flyover will allow trains to run more reliably at the busy junction to Heathrow airport and once operational, the Elizabeth line will allow passengers to travel from Reading and Heathrow in the west right through the capital without changing trains.
Matthew Steele, Crossrail Programme Director at Network Rail, said: "Once opened, the Elizabeth line will greatly improve the capacity of the transport network in London and beyond with new trains offering more frequent and more reliable services from Berkshire, Essex and the south east of London.
"I would like to thank passengers and our lineside neighbours for their patience over the bank holiday whilst we carried out these major works."
Matthew White, Surface Director at Crossrail added: "The Elizabeth line will provide a step change in public transport for people in outer London, Berkshire and Essex.
"The work carried out by Network Rail on these sections of the route will help to deliver quicker, more reliable services and better stations for many thousands of passengers."
Elsewhere, Acton railway station was given the green light for a major revamp as part of the Crossrail project.