Passengers on Southern rail, Merseyrail, and Northern are all being affected by strikes by members of the Rail, Maritime and Transport (RMT) union today.
The 24-hour walkout on Southern is the latest action in a long-running row over changes to the role of the guard. There is also an overtime ban in action by members of the train drivers' union Aslef.
Meanwhile, Northern staff are carrying out the last of a three-day walkout, and there's a Merseyrail strike today as well as on the 23 July – the last day of The Open golf championship.
The RMT says it is in dispute with the firms over so-called driver-only operated trains, which it says will be unsafe.
General secretary Mick Cash said:
RMT members on Southern, Northern and Merseyrail remain absolutely rock-solid and determined in separate disputes that have the common objective of putting safe rail travel before private profit.
RMT is available for serious talks but every approach we make is kicked back in our faces.
Northern said it was doing all it could to keep customers on the move, and would run more than 40 per cent of its timetable. Services are expected to be extremely busy though, and travellers have been advised to allow extra time for their journeys.
Merseyrail boss Jan Chaudhry-van der Velde said his team had put together "the best possible timetable" to provide a limited train service. Trains will run from 7am to 7pm, but some stations will be closed.
Southern, meanwhile, said today's action wasn't expected to have "any further effect" on services, though it cancelled around a quarter of its services to deal with the Aslef overtime ban.