Thousands of rail workers at different companies are in dispute over a number of issues, raising the prospect of coordinated and hard-hitting industrial action.
RMT and TSSA union members at South West Trains are voting for industrial action over 660 job cuts.
RMT members at National Express East Anglia are also balloting over 300 job cuts, while workers at First Capital Connect are voting against plans to cut the opening hours of 40 ticket offices.
Almost 1,400 RMT members at South Eastern Trains are to be balloted over job cuts and other issues. All these ballots close on Tuesday of next week, apart from the TSSA one at South West Trains, which is set to end on Wednesday of this week.
Around 7,000 TSSA members at Network Rail are balloting against a planned two-tier pension scheme. This ballot closes on 23 March.
Some 100 train conductors in the RMT union at London Midland depots at Bletchley, Northampton and Watford are to strike on Friday of this week and Sunday of next week.