This post was made by 1slos10 and explains the red light changing with the use of magnets on the bikes...
I work for the Department of Transportation, and deal directly with installation and the final inspection of Traffic Signals in our region. I have heard a few myths on various ways to trip the detector, such as: sitting the bike on the side stand, trying to trigger it with the starter, and a few others I can't recall. I can tell you from previous experience that these hardly ever work. The loop in the pavement is a single conductor 14awg wire wound in a circle in the pavement, usually 3 or more turns to reach the proper inductance usually in microhenries. There is usually a small amount of current ran through the wire, and when you pull over it in your car the metal on the chassis causes a disruption in the amount of current that returns back to the cabinet, this because current always wants to take the path of least resistance and tries to ground to the closest possible source, meaning your metal chassis. There are few ways to improve the sensitivity of the loop. One is on the loop detector, it has switches that start in value of 1 and go up to 12 usually. The higher the number, the higher the sensitivity, but to high can lead to cars in the nearest lane being detected. The other ways is to put more turns of wire in the pavement itself. The last is all traffic signals have a function called dual entry, what this does is if your on your bike, and heading say "south" and there are cars heading "north" it gives you a green at the same time the north movement get ones, unless there is and opposing left turn(a car turning left with the north movement), if there is you have to wait till the left turn terminates and you will get a green. We use this in the case of losing a loop in the pavement, it guarantees that you get a green when the oncoming lane gets a green. Use of any of these terms will keep them from treating you like a idiot, in fear that you, by reading this post know as much or more than they do. . Sorry for the long post, but it takes a lot of words to explain it. If you have a problem with a signal, start at city hall and if that don't work, right a letter to a State Representative or the Transportation Commissioner, those 2 usually get us jumping trying to get the problem fixed.
I work for the Department of Transportation, and deal directly with installation and the final inspection of Traffic Signals in our region. I have heard a few myths on various ways to trip the detector, such as: sitting the bike on the side stand, trying to trigger it with the starter, and a few others I can't recall. I can tell you from previous experience that these hardly ever work. The loop in the pavement is a single conductor 14awg wire wound in a circle in the pavement, usually 3 or more turns to reach the proper inductance usually in microhenries. There is usually a small amount of current ran through the wire, and when you pull over it in your car the metal on the chassis causes a disruption in the amount of current that returns back to the cabinet, this because current always wants to take the path of least resistance and tries to ground to the closest possible source, meaning your metal chassis. There are few ways to improve the sensitivity of the loop. One is on the loop detector, it has switches that start in value of 1 and go up to 12 usually. The higher the number, the higher the sensitivity, but to high can lead to cars in the nearest lane being detected. The other ways is to put more turns of wire in the pavement itself. The last is all traffic signals have a function called dual entry, what this does is if your on your bike, and heading say "south" and there are cars heading "north" it gives you a green at the same time the north movement get ones, unless there is and opposing left turn(a car turning left with the north movement), if there is you have to wait till the left turn terminates and you will get a green. We use this in the case of losing a loop in the pavement, it guarantees that you get a green when the oncoming lane gets a green. Use of any of these terms will keep them from treating you like a idiot, in fear that you, by reading this post know as much or more than they do. . Sorry for the long post, but it takes a lot of words to explain it. If you have a problem with a signal, start at city hall and if that don't work, right a letter to a State Representative or the Transportation Commissioner, those 2 usually get us jumping trying to get the problem fixed.