Tens of thousands of commuters have struggled to get to and from work again today as three rail companies went on strike.
The issue linking Southern Rail, Merseyrail and Northern Rail was the planned axing of on-board guards.
The union mounted picket lines outside stations, saying they were receiving support from the public for its campaign to keep a safety-critical guard on trains.
- Video report by ITV News Correspondent Sally Biddulph
Picket lines sprung up across northern England this morning, creating one of the biggest days of disruption since the railways were privatised.
Southern is embroiled in a row over changes to the role of conductors for almost a year, with the RMT now taking 30 days of strike action.
Merseyrail and Arriva Trains North are planning to introduce new trains in the coming years which will be driver-only operated.
One union representative told ITV News: "They failed to give us a guarantee of a second person on the train. And they failed to give us a guarantee that that person would retain the safety critical competencies - like the current conductor.
"We think that's completely unacceptable and is a less safe method of operation."
Disruption is worsening as more drivers than expected refuse to cross picket lines.
Merseyrail had hoped to run almost half its services, but "many" drivers took the decision not to work today.
The company said it was running around 20% of services, far fewer than previously advertised.
Trains were still running on most routes, every half an hour, but they were not stopping at every station.
Manchester Victoria train station appeared empty at 7am this morning, as members of the RMT union walk out on strike.
Tens of thousands of journeys will be affected today as union members stage a 24 hour strike on Merseyrail and Northern Rail services.
The strikes are likely to see more than half of all services cancelled in the North West.
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