Workers at Merseyrail have started a 24-hour strike in a dispute with the firm over driver-only-operated trains.
The action, which began at 00:01, coincides with the final day of The Open golf tournament in Southport.
Rail union RMT said it recognised "the severe impact" the strike would have but it had "no option but... to force the company back to the negotiating table".
Merseyrail said there would be limited services across the region.
A spokesperson said trains would still be able to get people to and from Royal Birkdale, where the championship has been held since Thursday.
However, there will be no rail services across the rest of the Merseyrail network.
RMT claims the driver-only-operated trains are unsafe and will lead to widespread job losses.
The union's general secretary, Mick Cash, said: "Merseyrail are completely ignoring the clear wishes of their own passengers, who overwhelmingly oppose the idea of driver-only-operated trains on their network."
"Merseyrail have repeatedly kicked all conciliatory approaches by RMT negotiators back in our faces and made it crystal clear that all that they are interested in is the union signing a surrender document, which gives them a free hand to rip apart the safety culture on the railway," he added.
Merseyrail managing director, Jan Chaudhry-van der Velde, described the action as "disgraceful".
"The RMT executive thinks nothing of doing down the Liverpool city region in its proudest moments," he said.
"This industrial action is nothing to do with safety. If it was, the RMT would never have agreed a staffing deal last month with Great Western Railway, which sees new trains introduced, some with guards on them and some operating only with drivers."