Ever wonder about the physics behind traffic signal sensors? The sensors measure changes in inductance, but that still leaves a lot of issues, like ferrous vs. conductive, and contributions of frame vs. wheels.
If you've got aluminum rims, your frame material doesn't matter, because they operate at high frequencies, where the key component is a conductive piece of metal -- not carbon fibre, you weight weenie -- that allows an induced eddy current (e.g. closed loop). Rims get closer to the wires than the frame, align the wheel with one of the wires, so the maximum number of magnetic flux lines pass through your rim. If the sensor is a figure-8 pattern, the middle wire is twice as sensitive as the edge wires.
California has codes designed to address the engineering of cyclists in intersections.
Isaac Asimov wrote an excellent short story called "Unique is where you find it" about a problem posed to an eager young chemist by his antagonistic professor. There, I've spoiled the story for you.