ScotRail is set to slash hundreds of services as part of a temporary timetable due to staff shortages amid a row over pay.
Around 600 services will be affected from Wednesday, with the rail operator claiming the move will “provide greater certainty and reliability” for customers instead of late-notice cancellations.
It comes after four unions – ASLEF, RMT, TSSA and Unite – rejected a pay offer last week.
Train drivers’ union ASLEF branded the provisional timetable “economic vandalism” as it considers a ballot for industrial action over the dispute.
Dozens of trains have been cancelled and services affected in recent days due to a lack of workers.
ScotRail said fewer train drivers than normal have been available for overtime or rest day working, as is their contractual right.
The temporary timetable will see 1,660 services operating daily from Monday to Saturday, compared with the usual level of around 2,250, a cut of 26%.
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The first and last trains on more than half of all routes will remain the same but services during peak times will revert to an off-peak service.
The publicly-owned firm said it is recruiting 160 new drivers, but some rest day working and overtime is “still needed to deliver a normal timetable”.
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Mark Ilderton, ScotRail service delivery director, apologised for the disruption.
He added: “We are operating services which the vast majority of customers use and are still using all the available trains in our fleet so customers can continue to travel.
“We want to resolve the pay dispute with the trade unions and remain fully committed to further discussions.
“We’re asking customers to check their journey on our website or mobile app, as train times will have changed.”
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ScotRail said planning is ongoing to support travel to major events, including The Open golf tournament in Troon.
Customers booked on services cut from the timetable can claim refunds with no additional administration fee or can use their tickets on an alternative service.
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Kevin Lindsay, ASLEF Scottish organiser, said the Scottish government was taking a “fantasy land approach” to industrial relations on the country’s railways.
He added: “Rather than slashing the timetable in an act of economic vandalism that will impact towns and cities across Scotland as well as Scotland’s rail passengers, ScotRail and the Scottish government must get serious about pay and urgently get back round the negotiating table with a serious and credible offer.
“The Scottish government and ScotRail need to understand quickly that investment in our railways includes investing in its most precious resource, its workers.
“We urge them to come back to us with an offer that is serious and that treats our members with the fairness and respect they deserve.”