Passengers face five more months of disruption during upgrading of the main Edinburgh-Glasgow rail line, the ScotRail Alliance announced today.
Trains will be replaced by buses after around 8:30pm between Sundays and Thursdays from September to December, and January to March.
Services on some lines which use part of the route will also start later on Sundays - around 11am - with replacement buses replacing earlier trains.
These include Perth-Dunblane-Stirling-Edinburgh trains.
The work to electrify the main line between the cities via Falkirk comes weeks after the end of more than four months of disruption caused by the closure of the Queen Street tunnel in Glasgow for track upgrading.
The project - the Edinburgh Glasgow Improvement Programme - is already running seven months behind schedule, with electric trains not now expected to start running until next July.
The Alliance warned there would be further timetable changes to follow, including on other routes.
The changes will operate from Sunday 4 September to 31 March, with a break for the festive period between 8 December and 7 January, when normal services will resume.
Passengers between Edinburgh and Glasgow are urged to switch to a secondary line via Bathgate.
Evening trains between Sundays and Thursdays from Glasgow and Stirling will run only as far as Polmont, with buses for the rest of the journey to and from Edinburgh.
Sunday morning trains between Glasgow and Inverness, Aberdeen, Dundee and Alloa will be diverted via Cumbernauld until 11am.
ScotRail Alliance infrastructure director David Dickson, from track owner Network Rail, said: “We understand the inconvenience this work will cause our customers, and every effort has been made to minimise disruption as much as we possibly can.
"We are urging people to check their journey now and certainly before they set off.
"We will have extra staff on hand at key stations to assist customers.”