Found this news on the thestar.com about 200 cyclists blocking the traffic on a big expressway in Toronto, Canada. The cyclists was able to shut down the road for almost half an hour as they cycled about 7 km before the police arrived. 4 people were arrested due to refusing to leave the road. Solidarity to them!

Seems like the great organization Critical Mass was behind this action. Critical Mass is a leaderless event where cyclists gather to protest for example the traffic that is killing our planet.
I have been a part of similar actions where we blocked a street. It was a lot of fun, but also a bit scary when the rich people with expensive cars wanted to run us over.

Here is some pictures (source is Toronto Traffic Cameras) of the protest in Toronto.