Members of the Rail, Maritime and Transport (RMT) union on Arriva Rail North (Northern) walked out for the 29th time since the row started.
Only a third of trains were due to run.
The company said: “We will be operating a reduced timetable with very few trains running before 9am and after 6pm.
“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.”
The union claimed crime has increased in the area served by Northern, saying it showed the need for guards on every train.
A Northern spokesman said: “Travelling to and from Northern stations is safe and it is inaccurate and misleading of the RMT to suggest otherwise.
“Over 100 million passenger journeys are made on Northern’s network each year and there is no evidence that crime at Northern stations, in particular those which are unmanned, has increased.”
RMT general secretary Mick Cash said: “RMT members are standing rock solid again this morning on Northern Rail in the continuing fight for safety, security and access on our trains and are angry and frustrated that the company continue to refuse genuine talks that could work out a deal that underpins the guard guarantee.
“Our members remain absolutely resolute in the campaign for a safe, secure and accessible railway for all while the German owners of the company are quite happy to take a reckless gamble with passenger safety.
“No guard on the trains, combined with the destaffing of stations, is a toxic cocktail that gives the criminals a free hand on Britain’s violent railways.
“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 have treated us with contempt and made a mockery of the talks process.”
Strikes will be held on Northern on the next three Saturdays, while RMT members on South Western Railway will strike for 48 hours from next Friday in the same dispute.