Workers from three train companies are to strike on the day of the Grand National.
Employees on Southern, Merseyrail and Arriva Trains North are to strike on April 8 in disputes over staffing and the role of conductors, the RMT union announced.
It could throw many travel plans into chaos as people flock to watch the Grand National in Aintree, Liverpool.
Many people travel to the Grand National at Aintree in Liverpool by train, so any disruption to Merseyrail services will hit those going to the biggest race in the world.
The RMT also announced that a planned strike on Southern - owned by Govia Thameslink Railway - on April 4 had been moved to the 8th after the company offered fresh talks if the industrial action was suspended.
General secretary Mick Cash said: "RMT members on Southern Rail have been fighting for safety and access to rail services for nearly a year now and it is time for the company to get out of the bunker and to start making some progress.
"There is no reason for Southern/GTR to drag their heels and RMT is prepared to meet on the 4th of April as they have requested.
"We now have plenty of breathing space to get talks under way and we would urge the company to seize the opportunity that our decision today has opened up for both parties and the union would prefer for the talks to happen sooner rather than later.
"RMT guards and driver members on Southern have shown incredible strength and resilience throughout the past year and have been clear from the off that this is not a dispute about 'who opens the doors' - it is a dispute about a safe method of operation and about the guarantee of that crucial, second safety-critical member of staff on Southern services.
"It is time for that fundamental issue to be addressed at the negotiating table.
"If Southern are prepared to agree to talks on April 4, or sooner, with meaningful proposals on the table that address the issues at the heart of the dispute, the union's executive would be in a position to consider the suspension of the current planned action."
A Southern spokesman said: "We have received no official confirmation from the RMT and will review our response when we do."
Richard Allan, deputy managing director of Arriva Rail North, said: "We are surprised that RMT has announced strike action for April 8 as we had been in contact with their officials in the last 24 hours to organise further talks.
"We have been clear that we want RMT, along with our people, our customers and stakeholders, to play a role in bringing our modernisation plans to life.
"We want to work with everyone on how we modernise the way we provide customer service and continue to run a safe and reliable railway."