Dannoxyz has the right idea: Moving metal is the important thing due to induction.
If it is a single induction loop then you should ride along on edge of the loop.
A single induction loop looks like this when cut into the pavement:
_______
\ /
\___ /
A double induction loop looks like this:
_______
\ | /
\_|_ /
and you should ride ride down the middle of it. (Sorry for the crude ascii art.)
The double loops are much more bike friendly as teh local DOT can turn the gain WAY up. The single loop ones can get false positives from vehicles in adjoining lanes is the gain is set high enough to detect a bike. The double loop ones will get cancellation from a vehicle in an adjoining lane so they can turn up the sensitivity enough to detect a bike.
If you are really in a bind you can find the highest concentration of magnetic metal in your bike (probably the headset) and drag that along one of the wires embedded in the pavement. I've never had to go to that extreme.
(In edit: I cannot get the ascii art to look right: spaces in the edit screen don't translate to the post properly. The single loop inductor is a trapazoid. The double loop inductor is a trapazoid that is bisected by a vertical line. Hope that helps.)