Rail commuters suffered cancellations and delays as the new winter timetable was launched.
Staff shortages, signalling problems and ongoing industrial action were among the issues affecting the network on Monday morning.
On Sunday Northern experienced staff shortages and trains were cancelled at short notice between Blackpool North and Preston.
Some early-morning trains operated by Northern on Monday were cancelled due to a shortage of drivers.
The operator's website listed the issue as affecting a number of services, including between Blackpool North and Manchester Airport, Leeds to York and Sheffield, and Darlington to Saltburn.
As of 8am on Monday, the Transpennine Express had 24 cancellations listed for throughout the day due to a shortage of crew or train faults.
Affected services included those linking Manchester Airport with Edinburgh and Newcastle, and trains from Liverpool Lime Street to Scarborough.
Stephen Brookes, Rail Sector Champion for the Cabinet Office Disability Hub and Minister for Disabled People, was frustrated by the cancellations between Blackpool and Preston.
He said: "Yet more train numerous Northern cancellations from Blackpool North. Two wheelchair using friends now dare not travel at weekends.
"Can we be told when will this short/no notice regular situation get resolved. We are tired of having a Monday - Friday service only."
A spokesman for Northern, which is running more than 2,800 services today, said: "The new timetable for Northern is working well so far today.
"The small number of delays and cancellations are due to operational issues including driver sickness, signalling failure and train faults.”
Passengers on Great Western Railway were being warned to expect cancellations, delays and fewer trains between Reading and London Paddington due to a fault with the signalling system at Maidenhead.
Due to strike action by the RMT union, travellers on South Western Railway (SWR) have been warned of fewer trains, earlier finishes and some replacement buses throughout December.
Services are expected to be affected every day until January 2.
Industry groups had previously promised more services, shorter journeys and new routes becoming possible across the country under the new timetable.
RDG said the industry had put "years of work into drafting, consulting and planning" for the changes.
But teething problems were evident when the new timetable came into effect on Sunday.
Train timetables are changed twice a year, in May and December.
The infamous botched change of May 2018 led to chaos, and passenger watchdog Transport Focus said travellers would be hoping for a smoother introduction with the latest changes.