Roadsworth began painting the streets of Montreal in the fall of 2001. Initially motivated by a desire for more bike paths in the city and a questioning of “car culture” in general, he continued to develop a language around street markings and other elements of the urban landscape using a primarily stencil based technique. In the fall of 2004, Roadsworth was arrested for his nocturnal activities and charged with 53 counts of mischief.
You can read his full story on his website.
I for one think its pretty amazing stuff, and wish I had seen it first hand.