Railway signal workers in Scotland are to be balloted for strikes in an escalation of a dispute over rosters.
The Rail Maritime and Transport union said hundreds of its members will vote on whether to launch a campaign of industrial action.
The move follows a row with Network Rail involving signallers in the Stirling area.
RMT general secretary Bob Crow said: "Despite RMT making every possible effort to resolve this dispute through negotiation, we have met with nothing but a brick wall and broken promises from management and as a result we now have no option but to move to a strike ballot across Scotland.
"The ballot is currently being prepared and RMT will advise on the timetable in due course."