The federal government's order to reduce train speeds as a safety measure following a fiery derailment in Saskatchewan will mean longer hours for rail workers, a union representative says.

Transport Minister Marc Garneau ordered all trains on federal rail lines with 20 or more dangerous goods cars cap their speed at 40 km/h, 32 km/h in metropolitan areas.

The 30-day order, which came into affect Friday, was issued in response to Thursday's derailment of a Canadian Pacific Railway train carrying crude oil east of Guernsey, Sask.

Greg Edwards, chairman of Teamsters Canada Rail Conference, said workers get paid by the mile, not by the hour.

"Obviously it's going to make our workday a lot longer," he said.

The derailment was the second near the hamlet in less than two months.The first occurred on Dec. 9, 2019.

As it's not yet known what caused the second train to leave the track, it's unclear how reducing speed will help, Edwards said.

"It's going to be slow; it's going to be inconvenient for everybody because it won't be just those trains that will slow down, the ones behind them will have to slow down as well."

Edwards admitted that at the end of the day, safety is key.

"So if it's in the interests of safety, until they work out what actually happens, we're just going to need to live with it."

In the meantime, Alberta is currently assessing the economic impacts of the slow speeds.

"We are currently assessing what effects, if any, Ottawa's speed restrictions could have for Alberta's exports," Kavi Bal, press secretary for the province's energy minister, said in an email.

"After proper assessment, if it is determined that the problem is with one particular section of rail, we'd hope that Ottawa could adjust its restrictions before the 30 days as to not adversely affect other lines," he wrote.

Immediately after the derailment, CP Rail released a statement on Thursday stating that they implemented a slow order on its crude trains.

"Until we better understand the facts relating to today's incident, it is prudent to operate with an abundance of caution. We equally share Minister Garneau's concerns, and remain committed to safe operations, as we always have been."

CN said it too will comply with the slow order while reviewing the impact of the cap on its operations.