The RMT union has announced more strike dates.
Industrial action will be held across four 48-hour periods on 13-14 and 16-17 December, and 3-4 and 6-7 January.
Services have been severely disrupted in recent months as the row over pay, working conditions and job security has continued.
But the RMT said the latest strike action would send "a clear message" that workers want a better deal.
Its members at Network Rail and 14 train companies voted last week in favour of further walkouts.
More than 40,000 RMT members are expected to take part, the union said, after its bosses held a meeting on Tuesday to decide on the latest dates.
The RMT said there would also be an overtime ban from 18 December until 2 January, meaning the union will be taking industrial action for four weeks in total.
Our teams will look to continue operations as normal where possible and notify you should a delivery be affected.
Source: BBC News