Dave Able with the Teamsters union for engineers says part of the problem is a shortage of manpower at the rail companies.
The railways run shorter trains in extremely cold weather so the brakes will work.
The CEO of Canadian Pacific Railway (TSX:CP) has said adding more locomotives would only serve to further slow down the system.
But Able says more locomotives could be added if there were sufficient crews to keep freight trains running.
Able says CP cut its staff by about 300 people in the West alone and is only starting to call workers back from seasonal winter layoffs.
“Our guys are in there working day in and day out and they’re getting fatigued," he said. "Everyone needs a reset ... and there’s just not enough people to fill the crews,” he said.
Able also said CP has not replaced hundreds of people who retired in the last year.
“With the attritions, they let it get down to the bare minimum.”
He also blamed recent changes to the way CP manages employees in local areas. He said it's now less efficient to get crews to where they are needed the most.
“They’ve consolidated the manpower and it isn’t as effective.”
CP Rail has said trains are hauling more grain than ever before and that the company is doing everything it can to resolve the backlog.
Earlier this month, federal Transportation Minister Lisa Raitt and Agriculture Minister Gerry Ritz announced that the government will impose penalties of $100,000 a day on CP and Canadian National (TSX:CNR) if they fail to meet a standard of moving 11,000 grain cars a week.