Teamsters Canada released what it said was a recording between a Canadian National Railway Ltd. supervisor and a conductor that demonstrated why the union is on strike at Canada’s biggest railway.

About 3,200 conductors and railyard operators took to the picket lines on Nov. 19 over issues such as working conditions and drug benefits. The first strike in a decade at Montreal-based CN Rail is rippling through the economy, curtailing shipments of everything from oil to potash and threatening to trim growth.

Listen here to recording of a CN Rail supervisor and conductor.

In the recording, a CN supervisor asks the conductor to move a train to a new location, at which point he and the locomotive engineer would be relieved by a new crew. The conductor says they had notified CN hours earlier of their need to be relieved and they were now resting after working for 10 hours and 20 minutes, according to a statement released with the recording on Monday. The additional driving would take several hours, according to the statement. The conductor ultimately didn’t move the train and was suspended for 14 days without pay as a result, the union said.

The incident occurred on Oct. 19, 2018 near Pickering, Ontario, the union said.

A spokesman for CN Rail couldn’t immediately be reached for comment.

The Teamsters Canada Rail Conference union, which has been without a contract since July, said CN Rail wants to make it more difficult to take time off and make employees work longer hours. It’s also protesting the practice of using remotely controlled locomotives to couple cars.

For his part, CN Rail Chief Executive Officer Jean-Jacques Ruest said last week in a statement that no employee is ever asked to work unsafely. “Any employee that feels fatigued or has safety concerns has a duty to report it and use alternative means to complete his/her assigned task safely.”

--With assistance from Sandrine Rastello.