And then someone rolls up with a bicycle, and because it doesn't have as much metal in it as the detector expects, they end up sitting at a red light forever. Been there, done that.
My local town has a roundabout with a cut-through lane for buses. The cut-through has a traffic light to help the bus emerge. Every so often, a (presumably non-local) car driver accidentally enters the bus lane, and then has to wait for the next bus to trigger the traffic light.
