A retired CN engineer says an order out of Ottawa to limit speeds of certain freight trains in urban areas will mean longer delays for drivers.

"People at the crossings in London will be waiting quite a bit longer because most of the trains now are up to 12,000 feet long," said John Wever, who spent 32 years as an engineer with CN before retiring two years ago.

Federal Transportation Minister Marc Garneau on Thursday placed stricter speed limits on trains that carry dangerous through metropolitan areas. His order was in response to a fiery derailment of a crude oil train near Guernsey, Sask., last week.

The order requires trains with 20 or more cars of dangerous goods to be limited to 20 miles per hour (32 km/h). Outside of urban areas, trains will be limited to 25 mph (40 km/h).

Before the order, trains were required to limit their speed to 64 km/h in metropolitan areas, and 80 km/h everywhere else.

The order took effect on Friday and will be in place for 30 days.

Garneau said he's "very concerned" about the number of recent train derailments of cars carrying dangerous goods.

Wever, who's operated trains in the London area, Quebec and in the United States, said drivers will notice the delays and said it will also have an effect on train crews.

For example, he said CN trains operating between Sarnia and Toronto can make that trip in a day under regular speed limits. But the stricter limits may make that difficult.

"If you've got trains going that much slower, there's a good chance you won't make it to Toronto, so they'll have to re-crew trains and incur more costs," he said.

But will reducing speed also cut down on the number of dangerous derailments?

A drone shot of the train derailment near Guernsey, Sask., approximately 100 kilometres southeast of Saskatoon. (Submitted by Philippe Gaudet)

"I would look more at the maintenance of the rail and the condition of the rail, as being more of a factor," said Weaver.

Garneau said the order limiting train speeds can be changed at any time based on new information.

"I recognize there are economic impacts," said Garneau. "But I cannot compromise on safety. I will not hesitate to take further swift action as is necessary."