I had to call the local transportation people in my city (PDX) because of an intersection where the cars turning left were constantly running OVER the bicycle symbol for MY left turn. They get so much in the habit that when there is actually a bike there its panic time for the cyclist, and when you are on a loaded tandem there just isn't any jumping out of the way! So I asked that the sensor be moved back from where it was. Turns out that when you have several loops in a row, any of them will pick up a bicycle, not just the one that is marked. Also, the way to make the sensor work, everytime: put your bottom bracket over some part of the loop wire! It really works. Since learning this I have never failed to trip a sensor. Just line up your BB with some part of the sensor loop and you are golden. Maybe someone mentioned this but I read 15 or 20 posts and then skimmed ahead.