Cycling advocates in Toronto are expressing outrage after a 40-year-old woman on a bicycle was struck and killed by a truck on Dundas Street West in what police say was a "preventable" collision.

The accident occurred around 11:30 a.m. near Sterling Road on Dundas, police said.

The cyclist, a woman in her 40s, succumbed to a severe head injury and other major trauma shortly after the collision.

Dave Meslin of the Toronto Cyclists Union said the death highlights the risks riders face on roads without bike lanes.

"It's not about drivers versus cyclists," he said. "It's about the lack of proper infrastructure on the streets."

The woman was killed after a truck travelling southbound on Sterling made a right turn to head westbound on Dundas, said Const. Hugh Smith.

The cyclist was on the same route and making the same turn and was "somehow" trapped under the truck, he said.

"Some of the marks initially we’re getting, [the truck] was making a tight turn, so probably not a lot of space for that cyclist to pass, if they were thinking of passing," said Smith.

Bike trailer may have been factor

Although the investigation is in its early stages, police say they believe the driver of the vehicle may have lost sight of the cyclist during the turn.

Smith said the bicycle was towing a trailer, which may have also contributed to the accident.

"Anything you attach to a bicycle is going to hinder your movement as far as the length of the turn, the amount of work it takes — the gear that you're in — for you to get through the turn," Smith said. "Most times we say a bike is designed for one person, unless it's a tandem."

Police haven't identified the woman and no charges have been laid.

"It's one of these preventable collisions," Smith said. "We have two road users going in the same direction, making the same turn and because we’re sharing the space, one has lost sight of the other, or one has continued into the path [of the other]."

Smith said he believed the woman lived in the area.

She is the second cyclist to die on Toronto roads this year.

Last month, Ontario's coroner's office announced it would investigate an increase in cycling deaths in Ontario between 2006 and 2010.

The coroner estimates between 15 and 20 cyclists die on Ontario roads every year from accidental collisions.

Although Dundas and Stirling were closed for a police investigation earlier Monday, the streets have since reopened.