City Engineering and I just tested the loop detector on Jackson at Broadway (heading toward World's Fair Park) and discovered that, contrary to most intersections, the most sensitive spot where you should position your bicycle is between the pavement cuts. (Usually it's on top of the pavement cuts--see below for excerpt from our Commute Guide.) Also, remember that there is a new state law that allows bicyclists to proceed through a red light when the loop detector (or video camera) doesn't detect them. You DO have to make sure it's really not working, and not use the law as an excuse to run any red light. http://state.tn.us/sos/acts/106/pub/pc0640.pdf
Some traffic signals are triggered by electrically charged wires buried in the pavement. When a vehicle stops over the wires, the metal disrupts the current, which sends a signal to the traffic signal control box. While a car is easily detected by the sensors, and a pedestrian can push a button to get the “walk” sign, a bicycle — with relatively little metal — must be in the right
spot to be detected.
You can recognize these sensors by looking for narrow cut lines in the pavement, usually in a rectangle shape. You should be able to activate the signal by positioning your bike on the pavement cut. If there are three parallel cuts in one lane, you should position your bike in the center of the lane, over the center pavement cut.
Also keep in mind that some traffic signals have very long cycle lengths and it may take a while to get served on a side street. Cycle lengths may be as long as one hundred and twenty seconds, and although two minutes may not sound like a long time, it may seem like an eternity when waiting for a green.
If you find a signal that is not working for bikes, please call 215-3815 or e-mail firstname.lastname@example.org.
Full Commute Guide at http://www.knoxtrans.org/plans/bikeprog/comguide.pdf