On most parts of Queen street, public transportation is run on street cars, or Red Rockets, as the Toronto Transit Commission (TTC) calls them. They are run on two tracks like a train, and as such, they also inheric the problems with trains -- they can not easily make turns at will and only run on defined routes. So when one of them is stuck, all of them behind it will be piled up, like you see in this picture. The best thing about them is that they do not pollute the environment.