Workers at the Amey rail contractor are in dispute over pay and conditions.
RMT union members have voted overwhelmingly to strike over the issues. TSSA union members have already taken action and have more planned for Friday of this week.
The TSSA and the firm met at the Acas conciliation service on Tuesday of this week.
If the talks do not reach a satisfactory outcome, TSSA members will strike from 2pm on Friday until 11am on Monday of next week.