Rail passengers in Scotland have been warned to expect months of disruption to their journeys as the rail network is upgraded.
They have been told that some journey times are likely to be longer on key routes between the central belt, the north and north-east of Scotland.
Some trains operating after the peak evening rush will be cancelled or diverted.
The work is scheduled to begin on 21 May and run until at least September.
But disruption to the line between Glasgow Central and Edinburgh, via Shotts, is likely to continue until work finishes on 7 December.
Queuing systems will also be in operation at key stations, ScotRail added.
The rail firm said the upgrade work was necessary to increase reliability of the rail network.
It will pave the way for "new faster, longer, greener trains" in Scotland, it added.
Jacqueline Taggart, of ScotRail Alliance, said: "No-one likes having their journey changed.
"However, this short-term disruption will lead to a more reliable, better rail network that will rank amongst the very best.
"We are going through a massive period of change on Scotland's railway.
"The work that we are carrying out over the next few months will bring about a revolution in rail - with more and better trains, more services and more seats than ever before.
"However, while we transform the railway, there is inevitably going to be some impact on people's services.
"We are doing everything we can to minimise this, and to keep people moving."
Breakdown of rail service disruption
- Glasgow - Alloa/Stirling/Dunblane/Perth
On Sunday to Thursday evenings after 20:00, until Sunday 10 September, trains may be diverted or cancelled. Replacement buses operate when there are no trains running. The last trains of the day heading north may depart earlier than usual.
- Glasgow Queen Street - Dundee/Aberdeen/Inverness
On Sunday to Thursday evenings after 20:00 until Sunday 10 September, services may be diverted via Polmont or cancelled. Replacement buses operate when there are no trains running. The last trains of the day heading north may depart earlier than usual.
- Glasgow - Falkirk Grahamston
On Monday to Thursday evenings after 20:00, until Thursday 7 September, trains may be cancelled. Trains between Glasgow Queen Street Low Level and Cumbernauld run as normal with replacement buses operating between Cumbernauld and Falkirk Grahamston.
- Glasgow Central - Edinburgh via Shotts
On Sunday all day and Monday to Thursday evenings after 20:00, until Thursday 7 December, trains may be cancelled or operate between West Calder - Edinburgh only at certain times of the day. Replacement buses operate when there are no trains running.
Customers can also use Lanark trains, which run as normal, between Glasgow Central - Bellshill in both directions.