Flashing green

I just flew my Mooney up to Vancouver (this is somewhat aviation
related). When I got there I noticed that sometimes the traffic lights
were just green and other times they were flashing green. I asked many
locals what the difference was and none of them knew. Some thought it
was related to the crosswalks but I noted no cooreleation between an
intersection having a crosswalk or having someone pushing the walk
button and the flashing. Perhaps I'm just being a nerdy engineer but
I'm really curious if anyone in Canada knows what this means.

-Robert