Rail bosses are confident that contingency plans could keep mainline routes open during a prolonged stoppage by maintenance staff, but acknowledge that a nationwide strike by signalers would immediately hit travel.

They fear that the three disputes may all come to a head over the Bank Holiday weekend, a move that would bring parts of the congested motorway network to a standstill.

The results of the maintenance workers ballot tomorrow is expected to give a resounding mandate to strike. Bosses still hope that the signalers’ ballot, which will be disclosed next Friday, may yet avert a stoppage. The results of a third ballot, of supervisors belonging to the TSSA union, will be announced this Friday.

The 5,500 signalers are in dispute over proposed changes to safety routines and work rosters. The 13,000 maintenance workers were balloted over plans by Network Rail, which runs the fixed railway infrastructure, to cut 1,500 jobs. The company claims that 1,100 have already agreed to take voluntary redundancy, but will not rule out the threat of compulsory job losses.

It is also trying to bring about changes to working practices, many of which were inherited from the nationalised British Rail. The company wants to change its maintenance roster so that workers can routinely be brought in on Saturday and Sunday nights, when fewer trains run and access to the tracks is easier, without having to pay overtime. Many maintenance staff are currently contracted to work Monday to Friday.

Robin Gisby, Network Rail’s director of operations, said: “I can’t live with the RMT holding the whole country to ransom. The union wants a cast-iron guarantee there will not be any compulsory redundancies. I cannot give that guarantee.”

He said that trains would keep running on the mainline railway even if maintenance teams down tools. However, smaller branch lines would see services curtailed or have speed restrictions imposed.

A four-day strike 18 months ago had limited impact on services.

Mr Gisby said that the workplace tensions were heightened by the political uncertainty ahead of a General Election. He also said that the RMT felt threatened by the loss of income that a reduced head count would bring. The union insists that proposed changes to the maintenance regime pose a danger to passengers and make a rail disaster “an inevitability”.

The last national rail strike was in 1994, when signalers held a number of stoppages during a three-month period.