Most of the intersections in the city where I work have a white X on the pavement indicating where to put your bicycle wheel in order to trigger the light. I always get a chuckle when I roll up to a light and cyclist is sitting there waiting off to the side or in front of the "X". I used to try to explain to them what the X was for, but most seemed annoyed, so I gave up.

I've seen city employees adjusting the sensitivity of the loops using a bicycle wheel setup almost exactly like the one in the photo earlier in this thread.