Talks aimed at averting strike action by Network Rail signalling workers have broken down without agreement.
Members of the Rail Maritime and Transport Union (RMT) will hold two 24-hour walkouts this week, in a row about rosters and transfers.
The stoppages, involving nearly 450 RMT members will start at noon on Tuesday and Thursday.
The train operator First ScotRail has warned customers that the action will severely disrupt services.
A limited timetable between Glasgow and Edinburgh is likely but it is expected that no trains at all will run north of Perth during the stoppages.
RMT general secretary Bob Crow said: "Network Rail is blatantly trying to unilaterally rewrite agreements without consulting the workforce."
But Network Rail's David Simpson denied claims that they were wishing to make changes to rostering hours.
"We apologise to all who would be affected by a strike which is outwith our control"He added: "Despite our best efforts to resolve this dispute, we are bitterly disappointed to inform passengers and freight operators that the RMT still intends to take strike action this week.
"We have been unable to shift the union from their position - a position that puts safety at risk by demanding safety assessments be voluntary, not compulsory.
"We have prepared a contingency train service which aims to reduce the impact on passengers as far as possible. Details are available from train operators and National Rail Enquiries."
Mary Grant, managing director of First ScotRail, said: "We will be disappointed if the dispute is not resolved and apologise in advance to all who would be affected and inconvenienced by a strike which is outwith our control."
Renewed discussions got under way on Monday morning, after eight hours of talks with the conciliatory body Acas failed to come to any agreement on Friday.
First ScotRail said customers should check its website for revised timetables.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~36~RS~)