ScotRail passengers are facing double disruption to Sunday travel, as engineering work takes place while trains have already been cut back in a pay dispute.
Several routes out of Glasgow Queen Street are affected - including Cumbernauld, Edinburgh, Aberdeen, Inverness, Oban and Fort William.
ScotRail apologised to travellers and said some trains would be diverted and buses would replace others on parts of the network.
A reduced timetable is already in place - with only about 50% of services running on Sundays after drivers declined to work overtime in a row over pay.
Routes affected
- Aberdeen/Inverness/Elgin: Revised times and trains diverted between Glasgow and Stirling.
- Edinburgh via Falkirk High: Trains will not call at Croy and Falkirk High. Buses replace trains between Glasgow Queen Street and Linlithgow.
- Alloa: Services between Glasgow Queen Street and Stirling at revised times. Trains will not call at Bishopbriggs, Lenzie and Croy, with buses between Glasgow Queen Street and Alloa
- Cumbernauld: Trains run at revised times with most extended to Stirling.
- Anniesland: No services as this route is affected by the cut back timetable
- Oban/Fort William: Buses replace trains between Glasgow Queen Street and Crianlarich.
- In Glasgow buses replace trains between Mount Florida and Neilston.
ScotRail advised passengers to allow extra time for travel and check their journey times on the mobile app.
Service delivery director Mark Ilderton said: "We're sorry for the inconvenience this may cause to customers who have their journey impacted by service alterations.
"We know how frustrating this can be and thank them for their patience."
Mr Ilderton added that ScotRail was "fully committed" to further discussion with unions in the driver dispute over pay.
The publicly-owned rail firm cut 600 services and introduced an emergency timetable after four unions turned down a pay offer earlier this month.
Aslef, Unite, RMT and TSSA have rejected the three-year deal backdated from April this year until 2027 which would see workers receive a 2% rise each April and a 1% increase the following January.
Drivers' union Aslef is balloting ScotRail staff over industrial action.
Aslef Scottish organiser Kevin Lindsay said the union would return to negotiations and described the reduced timetable in operation as "an act of economic vandalism".
He said: "It has not only inconvenienced passengers but also significantly impacted Scotland's economy."
Fair settlement
The train cutbacks have already affected travel to major events in July like the Open golf tournament and the TRNSMT music festival
Transport Scotland said it acknowledged the desire of rail unions to negotiate a fair settlement for their members
A spokesperson added: "Train planning and staff rotas are operational matters for ScotRail.
"However, we fully expect any timetable to give the best reliability and availability for passengers and that changes are communicated well in advance to enable effective journey planning."