Workers at three rail companies have begun a 24-hour strike on the day of the Grand National horse race.
The action, involving Southern, Merseyrail and Arriva Rail North, is part of an ongoing dispute over staffing and the role of conductors.
Merseyrail said choosing to strike on the day of the race meeting would damage Liverpool’s reputation.
Managing director Jan Chaudhry-van der Velde said the protest would “do immeasurable damage”.
Speaking after the company’s failed talks with the RMT union, he said the “eyes of the world” would be on Liverpool during the Aintree event.
The RMT said it would unveil a mobile advertising billboard to explain the reasons for the strike to racegoers.
RMT members are opposed to plans to introduce driver-only-operated trains, which they say would be unsafe and lead to widespread job losses.
Merseyrail has drawn up a contingency train timetable to combat the strike action.
Mr Chaudhry-van der Velde 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.”
Rail Minister Paul Maynard said it was “disappointing” that the strike was going ahead and called for conciliatory talks.
John Tilley, regional organiser for the RMT in the North West, said: “We don’t want to be out on strike. We want to be able to settle these issues.
“The bottom line is, on Northern, the proposal is to take guards off 50% of their services, on Merseyrail it’s 100%.
“That’s the point of the dispute and people need to be talking to us about that.”
David Sidebottom, director of the watchdog Transport Focus, believes the strikes are being “dumped on passengers”.
He said: “It is vital that all parties in this dispute get back around the table to resolve this matter.”
Merseyrail said services will operate every seven-and-a-half minutes “at key times” throughout the day.
The company said it had prioritised the route between Aintree and the city centre, with the replacement timetable in place between 11:15 and 13:30 BST and then between 17:30 and 19:15.
There will be fewer trains or no trains at all on other parts of the network, although replacement buses will run on certain lines.
Northern, the trading name of Arriva Rail North, said it had added six trains to its Liverpool Lime Street service to help racegoers travel home.
However, the company said its services would still be significantly reduced, and all trains were expected to be busy.
Southern also said it would also be operating a reduced service along some lines.,
Up to 2,000 staff at Southern rail, Merseyrail and Northern rail walked out on 13 March in the ongoing dispute but only limited disruption was reported.