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.