Workers at three rail companies are launching strike action amid bitter rows over staffing and driver-only trains which will disrupt travel for passengers, including racegoers attending the Grand National.
Members of the Rail, Maritime and Transport union (RMT) at Merseyrail, Arriva Trains North and Southern are walking out for 24 hours, with little sign of a breakthrough in the disputes spreading across the industry.
The strike at Arriva and Merseyrail coincides with the Grand National at Aintree, the biggest horse race of the year, which is attended by tens of thousands of people, many travelling by train.
Merseyrail is expecting drivers in the Aslef union to refuse to cross RMT picket lines, so a team of managers is being drafted in to provide a service before and after the race between Liverpool city centre and Aintree.
There will be a seven-and-a half-minute service at "key" times, but fewer or no trains on other parts of the network.
Rail replacement buses will run on some lines.
Jan Chaudhry-van der Velde, managing director at Merseyrail, said: "Despite the RMT's best efforts to scupper this iconic event and create misery for the tens of thousands of people who look forward to it all year, we've developed a timetable aimed at getting as many people between central Liverpool and Aintree as we normally do on Grand National day."
Arriva Trains North said its services will be "significantly" reduced, with the last trains leaving Liverpool Lime Street between 7.02pm and 8.16pm.
The operator said it had added six trains to its Liverpool Lime Street service on Saturday evening to help racegoers travel home.
Richard Allan, deputy managing director, said: "We are asking customers to plan ahead carefully. We are also asking customers travelling direct to Manchester to consider using other train operators' express services.
"This will help to free up space on Northern services that stop at many local stations not served by other operators."
The Merseyrail and Arriva disputes are over new trains coming into service in 2020 which will be driver-only, while the Southern row is now a year old, with the RMT taking its 31st day of strike action today.
The union will parade an advertising billboard through Liverpool and Aintree explaining why the RMT is taking strike action to defend safety-critical guards.
The RMT is demanding an inquiry and a halt to the introduction of driver-only services because of safety implications.
General secretary Mick Cash said: "It is well established that once the guarantee of a guard is withdrawn then disabled passengers are disadvantaged because they can no longer be assured of being able to turn up and get on or off the train at unstaffed stations."
The Transport Salaried Staffs Association said in a message to its members at Merseyrail: "TSSA members are advised to carry out their normal duties and attend for work at their normal times of work and for their normal rostered shifts.
"Members should decline to change their rostered hours of duty except in circumstances where their contract of employment allows their employer to change them."
Southern is aiming to have a near-normal service during the strike, saying nine out of 10 trains ran during the last walkout in March.
The company announced it planned to run a normal train service on all but one of its routes.
Passenger services director Angie Doll said: "We're now running a near-normal service on RMT strike days, so fewer people are being affected by the RMT's action. We plan to provide almost our entire normal Saturday timetable."
No Southern services will operate between Clapham Junction and Milton Keynes Central via Kensington Olympia/Watford Junction.