Rail passengers planning to travel today are advised to check for details of services after strike action called by the RMT.
Rail workers at two companies are said to be solidly supporting a fresh strike in the long-running dispute over guards on trains.
Members of the Rail, Maritime and Transport (RMT) union at Arriva Rail North (ARN) (Northern), as well as those at South Western Railway (SWR), walked out for 24 hours, with further strikes planned in the coming weeks.
Services were cancelled or disrupted, with buses replacing trains on some routes.
Northern said today it was operating a reduced timetable with very few trains running before 9am and after 6pm.
This could impact on runners coming to stay or dine in Newcastle the night before the run.
A Northern statement read: "We expect to run around 30% of services and all customers are advised to plan carefully if they intend to travel on the rail network.
"Unfortunately, on some routes, we aren't able to run services, while others have a limited service. On those routes where we are able to operate trains, we expect all services to be extremely busy. We also have replacement bus services available on some routes where trains aren’t running."
Northern said ongoing engineering work in and around Manchester will also see some disruption to services, particularly between Manchester and Liverpool.
Northern's statement went on: "On Sunday there will be planned cancellations on a small minority of routes, primarily in the north west, and again customers should check up to the last minute before travelling.
"This weekend also sees a number of significant events taking place throughout the north of England and customers are reminded of the impact the amended timetables will have on travel to and from those events."
The RMT announced a total of six days of planned strikes on consecutive Saturdays – 25 August, 1 September, 8 September, 15 September, 22 September and 29 September.
RMT general secretary Mick Cash said: "RMT members are standing rock solid again this morning on both Northern and South Western Railway in the continuing fight for safety, security and access on our trains.
"It is scandalous that while other train operators have been prepared to engage seriously with RMT on the crucial issue of a guaranteed second safety-critical member of staff on their services, ARN and SWR have slammed the door in our faces.
"It's time for both these companies to get out of the bunker and start talking with the union on the issue of the guard guarantee. RMT will not allow safety, security and access on our railways to be compromised in the drive for private profit."