After having moved my rectifier down to where the muffler bracket is, I've had a lot better luck. Some lights hardly change in a car though.

Cops and firetrucks use a radio frequency control device to force the light to give them a GREEN. Hang a ladder off your bike and have it registered as a firetruck.

So,  they sort of work.     I say sort of because some of the ones they sell do not.   I did some experimenting and found a magnet in my stash that worked on the Savage and it works on the Sportster (which has aluminum wheels and was worse at lights than the Savage)

What's the idea of how they work?  Well, the sensor wire in the ground has a signal (frequency) being passed thru it.   As steel goes over the loop it acts as a larger "center core" and that in turn changes what is called "inductance" (basically a fancy term for how magnetic fields affect wires , voltage, frequency etc etc)..  The change in inductance affects the time delays in the frequency circuits and the system senses the vehicle.    What the magnet does is have it's "field"  affect the sensed inductance ever so slightly and causes the system to "see" you.  Works best if you rock the bike a tiny bit.  

So, why do some not work.  It has to do with the magnetic field they put out. (remember your school science class where they put iron filligs on paper with a magnet under it)  Some of the magnets do not have a flied that extends far enough.  

 The Field has to go a few inches into the ground.  So, if you mount it on the bracket that the Calf. models would have the canister, it has to go somewhere around a foot or more out from the magnet.    

What I did to find the right magnet.....  I got a cheapo compass.  Then I set the magnets I selected on a wooden board on my concrete garage floor.  I checked each (one at a time) to see which magnet affected the compass the furthest out.   I found that a long skinny magnet (8 in x 1/4 in x 1/16 in) with the N & S poles on each end had the best field.   About 18 inches out.  The funny thing was it didn't have the strongest pull.    I have seen some of the magnets they sell, and I have one from another project I did. Well, they only go out maybe 6 to 8 inches since the N & S poles are on the flat sides, not the ends.  

One thing I was thinking of trying,  tear apart my son's old "connectx" (spelling) magentic toy and take the little magnets and stack then together and put them in a stray and see how far the field goes out.  

This can be almost as bad as an oil thread.
We should all just use Klotz oil and that will eliminate any problem with sticky red lights.  

OK.  Those traffic sensors are "inductive loop sensors".  There is an oscillating signal going on in them all the time.   What a large metal object (I.E. CAR) goes into the oscillating magnetic field generated by that oscillation, it changes the inductance of the loop, and that changes the frequency of the oscillation and that is what triggers the light to change.
It is, really, just a big ol' metal detector that is buried under the road.
Magnets don't have much of an impact on those.  It is the mass of metal that is a car.  And not really just the mass, but how it is "seen" by the loop.
If you get a piece of sheet metal and lie it flat on the loop, it will likely trigger.  If you stand it straight up, it might not.

I know many of you will say I am wrong.. that's OK.
You say a magnet will induce a current in the loop. So what?  You need to change the frequency of the oscillation, not induce a current.
The key word here is oscillating.

If you insist that the magnet is the thing to use, then take your magnet, get a metal detector, and see how well the detector senses your magnet.  If it picks it up better than a similar piece of metal, use it.

Best thing to do is call the local authority that fixes the stoopid traffic light thangs and have them come out and adjust it!!!


http://marshproducts.com/pdf/Inductive%20Loop%20Write%20up.pdf