Rail passengers are facing delays after the closure of Reading station until after the new year, in the first step of an £850m overhaul.
Network Rail is beginning its remodelling of the station, which will include five more platforms, two additional entrances and a new viaduct.
Major re-signalling works means no trains from 27 to 30 December.
The lifting into place of a new railway bridge will also reduce services.
The station will reopen on New Year's Eve and trains will operate a bank holiday timetable.
Until then, many local passengers will have to use replacement buses, but inter-city trains are being re-routed through the Chilterns and Oxford for Bristol and Wales, or through Waterloo and Basingstoke to reach the West Country.
Dan Payne, of rail operator First Great Western, said: "One of the things that we've learned in the last couple of years is that customers want to stay on trains rather than use bus replacement services wherever possible.
"So that's exactly why we've planned what we've done at the moment."
Caversham Road will also be closed from the evening of 30 December to the morning of 3 January while the bridge is lifted into place.
The new 1,000-tonne railway bridge will eventually carry rail track to new platforms.
It is hoped the station and road will reopen on 4 January, the first working day after the new year.
Work to reorganise traffic flows and road layouts around Reading town centre ahead of the project began in June.