Workers on London’s Elizabeth Line will strike on January 12 in a dispute over pay and pensions, Prospect and the TSSA rail union announced.
Travellers have also been warned that the Elizabeth Line will have a reduced service on Saturday, with passengers advised to complete their journeys by 2pm. It will be closed on Christmas Day.
In addition, TSSA members at CrossCountry, Great Western Railway and West Midlands Trains will walk out between December 26 and 29.
The next strike from the RMT rail union starts at 6pm on Saturday - Christmas Eve - until 6pm next Tuesday. More two-day walkouts are due on January 3 and 4, then January 6-7.
The post-Christmas strike announcement comes after passengers using mainline railways were warned that the last trains leaving the capital will depart around 3pm on Saturday.
Parts of the London Overground will stop running from around 11am and the Elizabeth line from 2pm on Saturday and some sections of the Tube will also close earlier than normal.
Transport for London said there would be a reduced service on the Overground, and advised passengers to complete their journeys by 11am on its Stratford to Richmond or Clapham Junction, Gospel Oak to Barking Riverside, and Romford to Upminster branches.
Journeys on the Overground between Euston and Watford Junction, Highbury & Islington and Clapham Junction, Crystal Palace, West Croydon and New Cross and services out of Liverpool Street to Enfield Town, Chingford and Cheshunt should be completed by 1pm.
The Overground will be fully closed on Christmas Day and Boxing Day.
