A video of a cyclist getting struck by a car door at a stop sign in Vancouver is generating attention and debate over who might be at fault.

In the video, which was posted on YouTube last month, cyclist Heather Rosensweet can be seen passing a car just as the rear passenger door opens, knocking her to the ground.

"It was shocking ... I wasn't ready for it," said Rosensweet.

A passenger in the car got out and looked at her before the driver got out and made a phone call.

Rosensweet said she wasn't injured, but it did take her a moment to get back up after the accident.

"I was laying there thinking, am I hurt?" she said. "I feel really lucky I was OK."

Rosensweet said this was the first time she'd been in an accident in the seven years she's been cycling to work. She said she passed the car because there was plenty of space, and she needed to press the button to activate the light at the intersection — something she does everyday.

"I'm really careful," she said. "I don't feel like I did something wrong."

Melvin Lau recorded video of the incident while cycling to work with his GoPro on his helmet. He says, with more bikes and bike lanes on city streets, he regularly records video of his rides for safety and education, but this was the first collision he recorded.

"I think it is both an education for cyclist and drivers. I think there is a bit of a learning curve for everyone," he said.

Nevertheless, after he posted the video on YouTube, it stirred up debate online about who might be found at fault if such a case ever did end up in court, with many people saying either the cyclist or the passenger is to blame.

Who was at fault?

Vancouver lawyer Joe Murphy, who specializes in collision and accident claims, told CBC News it might not be who you think.

First of all, Murphy says, it is not illegal for a cyclist to pass a stopped vehicle on the right.

He points out that cars often pull around a vehicle that has stopped to make a left hand turn, and that's perfectly legal for a cyclist too when there is space on the road.

"That car didn't pull over as one would normally expect one would when one is dropping off a passenger. It stopped as one normally would at a stop sign."

"Obviously a cyclist has a duty to keep a look out and expect what one would reasonably expect, but in that case I didn't see anything that should have alerted the cyclist that this passenger on the passenger side would be opening that rear door," said Murphy after watching the video closely several times.

Murphy says, a provision in the Motor Vehicle Act says, a driver can't open his door unless he has checked first that there is no traffic coming.

He says this case is unusual because collisions between bikes and doors usually happen on the driver's side, but that did not happen in this case.

Nevertheless, he believes a judge would rule the driver of the car has a responsibility to drop off passengers safely, and in his opinion that appears that did not happen in this case.

"Everyone knows cyclists need to ride along the side of the road, between the parked cars and the cars moving along the roadway," says Murphy.

"I would think if that case went to court, the judge would find that most of the fault lay with the driver of the car and the person who opened the door."