Only around one in five train services across Britain are expected to run later as rail workers take part in their final walkout.
More than 40,000 rail, maritime and transport union members across 15 rail companies and Network Rail are on strike.
The action is part of an ongoing dispute over work, pay and conditions.
Services will start later and finish earlier and people are being urged to avoid traveling unless absolutely necessary.
TSSA union members who staff station cashiers and work in onboard operational roles will also be on strike, affecting Avanti West Coast, c2c and Transpennine Express services.
Around half of the rail network will be closed all day and trains will only run between 7.30am and 6.30pm BST, with services starting later than usual on Sunday as workers return to their duties.
This is already the third strike related to rail transport this month. The RMT, TSSA and drivers’ union Aslef took action last Saturday – affecting about 90% of services – and Aslef members walked out on Wednesday.
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In a letter to Transport Minister Anne Marie Trevelyan, RMT general secretary Mick Lynch said he hoped an agreement could be reached between the union and rail companies.
But he said “to achieve this, your government must loosen the handcuffs of the train operators who are currently taking their mandate directly from you”.
In response, a Department of Transport spokesman called on union bosses to “work with their employers, not against them” when agreeing on the way forward.
“Our railway is in desperate need of modernisation, but any strikes will only punish the people who stand up to the unions and push passengers further away,” they said.
Manuel Cortes, general secretary of the TSSA union, called the workers’ demands “reasonable” and said his members deserved a pay rise after several years of wage freezes.
“We are calling on the employers and the government to open negotiations to find solutions to the problems rail workers have with regard to pay, conditions and job security,” Cortes said.
Passengers who need to travel on a Saturday are advised to check the National Rail Inquiry or their train operator’s website for when their last train will depart.
Network Rail chief negotiator Tim Shoveller said: “Despite our best efforts to compromise and find a breakthrough in talks, rail unions are determined to continue and coordinate their strike action.
“This means rail workers are unnecessarily giving up an even bigger chunk of their pay, passengers’ lives are once again disrupted and the railway’s recovery from the pandemic is further damaged.”
Separately, there will be further strikes on Monday in Scotland after the RMT rejected ScotRail’s 5% pay offer, which it described as a “kick in the teeth”.
ScotRail warned of “significant disruption” to services and said it would run “very limited” services on just three routes on the day.