I was talking to one of my friends named Ralph Boaz about the subject of bicyclists turning traffic lights green. You see, Ralph is a Transportation Engineering Consultant with Pillar Inc. So he knows all about what makes traffic flow better and where to put traffic lights and stuff like that.
So here’s what he told me:
In actuated traffic signals (not those just on fixed timing plans), there are various types of detection methods including: Inductive Loops (wires in the ground), Video Detection, microwave, and others. Inductive Loops are the most common. An Inductive Loop is somewhat obvious because a groove has been cut into the road, the wire has been dropped in it and it is then filled with sealant that can be seen from the surface.
While there are preferred loop designs for bicycle detection (see http://www.humantransport.org/bicycledriving/library/signals/detection.htm and http://www.humantransport.org/bicycledriving/library/signals/green.htm), the average loop should be able to detect a bicycle with metal rims (any type). The key is for the cyclist to cross the loop over the most wire. On diamond and oval loops, cross left or right of center. On a square loop, ride down the right or left edge. On a quadrupole loop (often looks like a box with a line down the center), ride down the center line.
Photo courtesy of Human Transport.
Loops can get damaged or may need to be tuned. If you find that you cannot actuate the signal (be careful practicing), call your local traffic department.