The deadline to install winter tires on cars in Quebec is this Friday – but it doesn’t apply to STM buses.

They don’t use winter tires; they use their own system that includes deepening the grooves on tires to improve traction.

The transit corporation says it is not required to have winter tires, claiming there is a gap in the market and certified winter tires simply don’t exist, even though several tire manufacturers make winter-specific tires for trucks and buses.

Instead, regular tires are modified by Nov. 15 every year to meet STM standards.

“So what we do is we provide our buses with new tires on the front and traction tires for the rear wheels. It is really sort of a homemade recipe but that works for us,” said Philippe Dery of the STM.

It works for the most part – the STM called the 12 minor incidents after the most recent snow storm “normal.”

“In rush hour we have 1,400 buses on the road so unfortunately incidents are bound to happen, but luckily there were only a few of them,” said Dery.

The city said it spreads salt before the snow falls and several times after. Still, multiple buses got stuck, forcing drivers to turn around.

“Unfortunately the one on Cote-des-Neiges happened near a busy intersection where many bus routes came so it had a larger effect overall. It was a normal day for the STM,” said Dery.

Transit agencies in other Canadian cities also do not use specific winter tires, with tire manufacturers saying buses do not need them because they travel slowly.

In several cities transit agencies use chains on buses, while this year Vancouver's city buses will be experimenting with lightweight kevlar "socks" that wrap about rear wheels.