RMT union General Secretary Mick Cash said: "The union's position on Driver Only Operation (DOO) is perfectly clear".
Rail workers and unions argue that the move to DOO trains presents a safety risk to passengers, and will ultimately be used by management to reduce staff numbers and bring costs down.
Northern train drivers and guards walked out on a 24-hour strike on Monday in a row over the future role of guards as bosses want to trains to be operated exclusively by drivers.
"RMT members on Southern have shown incredible courage and resilience in the year-long battle to put passenger safety before private profits".
"Trains were still running on most routes, every half an hour, but they were not stopping at every station".
Northern, which connects cities including Leeds, Manchester, Sheffield and Newcastle, plans to run around 40% of its services, stopping in the early evening.
Speaking from the picket line at Buxton train station one member of the Rail, Maritime and Transport union said: "This strike isn't about more money, it is about protecting passengers and keeping the trains safe for everyone to use".
A spokesman told the Guardian Southern has drafted in staff from elsewhere in the business to work as contingency on-board supervisors and conductors. "This action could have been avoided if Arriva hadn't back pedalled from earlier pledges to retain the guard".
They say that in 2014 the revenue income of Merseyrail was £51 million, and Merseyrail paid out a dividend not far short of £14 million meaning a quarter of passenger fares ending up in the pockets of Merseyrails owners, Serco and Dutch state owned Abellio.
@northernassist It was easier to get into work today with industrial action, limited service but empty!
Merseyrail described the new fleet as "affordable" and said that they would be in public ownership.
No trains were being operated by Northern and Merseyrail before 7am and after 7pm.
Now the on-board train guard operates the opening and closing of carriage doors, but the new investment will mean this responsibility will be down to the train driver alone. "All these agreements cover new, modern, faster trains that are being ordered for these franchises".