Workers on Arriva Trains North have started voting on whether to launch a campaign of industrial action in a dispute over the role of guards.
Members of the Rail, Maritime and Transport (RMT) union are being balloted in the latest row over staffing on the railways.
More than 1,200 union members will be involved in the vote, which closes on February 28.
RMT general secretary Mick Cash said: "The union's position on driver-only operation (DOO) is perfectly clear.
"We will not agree to any extensions of DOO and will fight to retain the safety-critical role of the guard and to keep a guard on the train."
A company spokesman said: "Our focus is on protecting the jobs and pay of our people as we work to implement a modernisation programme that will maintain high safety standards, deliver better journeys and improve customer service.
"We therefore believe RMT is very premature in starting a ballot of conductors to vote for strike action.
"We want to agree a constructive resolution to this dispute and to continue the discussions we have started with RMT. Should any strike action go ahead, we want to reassure our customers that we are preparing plans to keep them moving."