Mot of the urban roads I ride have traffic-actuated lights. I stop where the inductive loop is in the pavement, or else the light won't change.

By law, in Washington State, the pavement should be marked where the loop is most sensitive for bicycles, unless it's most sensitive in the center of the lane at the stop line. So, if an intersection isn't marked, and if I can't see the pavement cut for the inductive loop, I stop in the center of the lane, just at the stop line.