Originally Posted by Mchaz

Taken from here: http://bicycleuniverse.info/transpo/...g-signals.html

"I read your article on triggering traffic signals with a bicycle and would like to tell you a few facts about vehicle detectors as I am a designer of these units. Firstly, magnets have no effect at all on loop detectors (unless of course the magnet is so big that it acts more like a big mass of metal.) If you want to trigger the traffic lights with 100% certainty, simply get off the bike and lay the front wheel of the cycle flat over the loop towards one corner for a second or two. The rim of a cycle wheel acts like a big short circuited turn of wire and used in this way will produce a bigger signal than most automobiles do. The reason for this is that you can place your wheel flat on the ground so that it is about 10 x closer to the loop than most automobiles can reach."

Also see this article, and the links he gives at the end: http://www.bikexprt.com/bicycle/actuator.htm

Originally Posted by SoonerBent

I used to be the field manager for a company that installed vehicle detectors. Let me add my .02 worth.

Detectors will pick up non-ferrous metal, however, ferrous metal is detected much more easily.

It doesn't matter the shape of the metal being detected, a cube, sheet or hoop all look the same to a detector. It's mass that's important, the metal of the vehicle adds to the force of the magnetic field created by detector. This is done by intersecting the lines of the magnetic feild created by the detector so mass the important factor. The more magnetic lines you intersect, the better. That's why laying a bike over the loop will work better than a standing bike.

The magnet idea is ridiculous. A magnet will not create a difference in the magnetic feild of the detector loop that will cause a difference in the current through the loop, which is what the electronics of the sensor actually detect.

Here is a very good article on the subject.
http://www.hgsc.bcm.tmc.edu/~havlak/...detectors.text

SB