Hundreds of union members at three train operators are set to take part in strike action immediately after Christmas in a dispute over pay and conditions.
The Transport Salaried Staffs Association (TSSA) stressed the action will have a "severe impact" on services, especially in the Midlands and South West.
The union said strike action will begin on CrossCountry from 9pm on Boxing until 9pm on 27 December while members at both Great Western and West Midlands trains will walkout from midday on 28 December for 24 hours.