The RMT, whose members went on strike throughout the country over three days in June, announced three strike dates, one in July and two in August.
Tricia Williams, chief operating officer at Northern, said: “We’ve taken on board learnings from the previous RMT strikes last month and have done everything we can to offer a skeleton service on the parts of our network where we’re able to - but our advice remains not to travel.
“The timetable we have put in place has been agreed with Network Rail, who have had to consider the requirements of other train operators and freight services on the network.
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“We apologise in advance for the disruption and inconvenience that the RMT’s industrial action will cause. Services are also likely to be disrupted on Thursday, 28 July given the impact of the strike on fleet displacement across our 550-station network. Customers should check online before they travel.
"We continue to be keen to speak to the RMT to find a resolution and avoid any future strikes.”
Northern is also advising customers to check before they travel on Thursday, July 28 as some services may have been affected by the previous day's strike action.
In short, the skeleton timetable comprises hourly services between 7.30am and 6.30pm from:
Leeds to Sheffield via Wakefield Westgate
Leeds to York via Micklefield
Leeds to Bradford Forster Square
Leeds to Skipton
Leeds to Ilkley
Ilkley to Bradford Forster Square
Skipton to Bradford Forster Square
Darlington to Saltburn
Liverpool to Alderley Edge via Chat Moss, Manchester Piccadilly and Manchester Airport
Customers should visit northernrailway.co.uk/strikes for the latest advice and travel information.