this is true in Seattle; not sure about where you live:

"As far as bicycle detection is concerned, I suggest that you center the bicycle in the center of the lane with the front wheel approximately 2 feet from the stop bar or crosswalk bar. If you have a particular intersection that does not seem to "see" you, I would like to know about that as well. We are often able to change the sensitivity of the detector to help better detect bicycles.”

I received this information from a city streets employee.

oh, and hey, on some of them, it works.

If any of you seattle people know of a bad actuator, PM me and i'll give you the lady's email and contact info