Rail passengers face disruption as Northern staff stage a 24-hour strike, days after travel chaos when new timetables were introduced.
RMT union members at Northern are striking for 24 hours on Thursday in an ongoing dispute about safety involving driver-only operated trains.
The union said Northern had declared "war on passengers".
Northern called for "meaningful" talks and said the majority of trains running would be between 07:00 and 19:00 BST.
The firm faced widespread criticism over cancellations, delays and the implementation of a new timetable on Monday.
The government announced urgent plans to deal with Northern's "poor performance", which the transport secretary Chris Grayling will discuss with leaders from the north of England later.
The meeting comes as Thursday's strike from 00:01 to 23:59 BST is set to be followed by similar action on Saturday.
A spokesman for Northern said it expected the "trains and any replacement buses we operate to be extremely busy".
Passengers have been told to allow extra time for journeys, "plan carefully and consider whether travel is necessary".
The majority of available trains would run between 07:00 and 19:00 to get people "into work and home again", Northern said.
Anthony Smith, chief executive of the independent watchdog Transport Focus, said Northern's passengers "have had a torrid time recently and these strikes will mean yet more cancelled plans and disrupted journeys".
"It is vital that all parties in this dispute get back around the table to resolve this matter without bringing the railway to a standstill," he added.
The latest strikes are going ahead as Northern "refuse point blank to engage in talks", according to RMT general secretary Mick Cash.
He said the operator had shown it was "not capable of running a railway" and had declared "war on passengers and staff in the drive for increased profits".
The union said passenger safety would be put at risk by getting rid of guards and extending driver-only services and has been in dispute with five operators for more than two years.
Northern's deputy manager director Richard Allan said it was "disappointing" the union had targeted the bank holiday weekend and "the first week of the new timetable".
"We urge RMT to move away from its nationally co-ordinated strikes and allow its local representatives to engage in meaningful discussions with us on how we better serve customers."