Ottawa's transit union is once again raising concerns about how OC Transpo's double-decker buses handle wintery weather after another bus went off the road in storm conditions on Friday.

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A double-decker OC Transpo bus slammed into a hydro pole along Woodroffe Avenue Friday morning during wintery storm conditions. (CBC)

The double-decker bus was heading south along Woodroffe Avenue Friday morning went it went off the road between West Hunt Club and Slack roads, slamming into a hydro pole and knocking out power to thousands of people.

The driver, the only person inside, wasn't injured.

It's not the first time one of the relatively new buses have gone off the road in bad conditions in the same stretch of empty fields.

During a winter storm on Dec. 21, a double-decker bus flipped onto its side on Woodroffe Avenue near Fallowfield Road.

In that case, the driver was also alone and managed to crawl out of a window uninjured.

"We were hoping that it was a one-off, that it was just a fluke, but unfortunately it doesn't seem that it is," said Craig Watson, head of the Amalgamated Transit Union Local 279.

"I think we need a full investigation, we need to check again on wind speeds out there, this obviously is something that needs to be monitored. … We're going to have to make sure that there's something done to ensure that these buses don't end up going into the ditches out there," Watson said.

"It's like a sailboat. You're going down the road and that is an extremely windy location in the city. I saw some of the tweets today from people who were out there today saying just how windy it was out there, so it's the location."

City is investigating

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This double-decker bus flipped onto its side and into the ditch along Woodroffe Avenue near Fallowfield Road during a winter storm on Dec. 21. (CBC)

Planting a line of trees could block some of the wind along Woodroffe, Watson said, adding that widening the road could also keep buses away from slush along the shoulder.

In an emailed statement, the city's general manager of transit said the bus wasn't in service at the time and that the city is relieved the driver wasn't injured. John Manconi also said the city is investigating.

"I have spoken to [Watson]

 … and it has been confirmed that as we do with any collisions, we will conduct a thorough and detailed investigation. Input from operators, supervisors and unions will be included as we do with every investigation," Manconi's statement reads.

"The double-decker buses are a safe and reliable part of the OC Transpo fleet, and have been thoroughly tested for safety."