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By Dearbail Jordan
Business reporter, BBC News
Train journeys are expected to start later on Tuesday following the latest round of strikes by rail workers.
Members of the RMT union who work for Network Rail will end a walkout at 06:00 GMT on 27 December.
However, it means many trains will not begin running until between 09:00 and midday.
Network Rail said that 70% of services will be operating but has urged passengers to check their travel times with train companies.
"Staff are returning to work so it is [a] much later start-up for passenger services," a spokesman for Network Rail said.
"Passengers should really check before they travel so they don't just turn up at a station for no trains to be there."
ScotRail said it will start to restore some services from about 07:15 but warned there would be some disruption throughout the day.
"Routes across the country will see services start up later than normal due to signal boxes opening at different times following industrial action," it said.
Thousands of RMT members across Network Rail, which operates and maintains the rail system, and 14 train companies have been engaged in strike action in a row over pay and conditions.
It coincides with wider industrial unrest across a number of sectors including nurses and ambulance drivers as well as Border Force workers at six of the UK's biggest airports.
Employees are walking out over pay at a time when the rate of price rises, or inflation, is running at a 40-year high.
Rail strikes will restart between 3 and 4 January as well as from 6 to 7 January.
In the meantime, there is an overtime ban by RMT members at 14 train companies which is scheduled to run until 2 January.
Network Rail said that 70% of normal services will run on Tuesday which it hopes will increase to 90% in the days ahead.
However, it expects this will drop to 20% of normal services once the next set of strikes begins in early January.
Mick Lynch, general secretary of the RMT, said: "The union remains available for talks to resolve this dispute.
"But until the government gives the rail industry a mandate to come to a negotiated settlement on job security, pay and condition of work, our industrial campaign will continue into the new year, if necessary."
A spokesman for Network Rail said: "The only way we're going to resolve any industrial dispute is by negotiation and by talking so of course we'll look to sit round the table.
"It is just unclear at the moment where we can go as all the cards we have to deal are already on the table."