No trains at all are expected to run on the Airedale and Wharfedale lines on Saturday 1st and Wednesday 5th October because of planned strike action.
Operator Northern says customers should not travel on those dates, nor on Saturday 8th October - though a 'handful' of services will run on the third strike date.
Members of the RMT and Aslef unions are walking out as part of their ongoing dispute.
Northern says there will be no services across its network - including on the lines into Leeds and Bradford from Skipton and Ilkley - on the first two strike dates, and just a 'skeleton timetable' on the third date.
Given the impact strikes have on fleet displacement, Northern is also advising customers to ‘check before you travel’ on Sunday 2nd and Sunday 9th October, when services won't start until much later in the morning.
For more information, Northern's customers should visit: northernrailway.co.uk/strikes
Tricia Williams, chief operating officer at Northern, said: “This is the fourth ‘Do Not Travel’ notice we have been forced to issue this summer due to strike action by the trade unions.
“We apologise in advance for the significant disruption and inconvenience this action by the RMT and ASLEF unions will cause to our customers.
“As we have previously pledged, we will continue to work towards a resolution to this issue with the hope of avoiding more disruptive strikes in the future.”
