There's a lot of misinformation in some of the previous posts. Since I spent a half day with a local traffic engineer about a year ago let me share what he taught me. I had called the Minneapolis city engineering office and complained about a traffic light near my house that I could NOT trip, nor matter what I tried. While I could have gone through it legally I asked for help from the city to solve the problem.
He met me near the intersection where the traffic control box was located and explained the operation of the lights. Seems the coiled wire under the street surface is part of an oscillator circuit, it's the inductor, while the capacitor is in a mocule in the signal control box. This oscillator operates at one specific frequency UNLESS disturbed by a change in the inductance of the coil -- as when ferrous metal comes in proximity. Like when a car or truck drives over the coil. The mass of iron or steel acts to change the inductance of the coil and the frequency of the oscillator. A discriminator circuit detects the change of frequency, and if it's large enough, begins the electronic sequence to change the signal.
A motorcycle doesn't usually have enough ferrous metal in the frame to do this, hence no change.
In the past these control boxes had an adjustable oscillator OR discriminator circuit that could be "tuned" so that even a small change in frequency tripped the light. The newer signals use a sealed circuit, potted in some sort of compound and there's no means of adjustment. This engineer found one of the older, adjustable modules in a desk drawer and lo and behold it worked. He adjusted the module to detect my motorcycle reliably, although it took a couple of tries with me riding back and forth a few times. It's been working fine for several years now, but many other signals don't.
The MN legislature passed a law allowing a left turn on red IF no traffic is coming AND if you've waited a reasonable time. Seems "reasonable" is determined by the officer, so citing you is still possible. The state did a fairly good job of notifying people and I suspect most motorcyclists here know of the change.
The magnets that are sold work in a limited way to trip the light. They cause an induced voltage as they pass over the coil and that changes the inductance and the oscillator's frequency -- IF the speed of motion over the coil is high enough to induce enough voltage. A slow speed drive-over won't usually accomplish this. Stronger magnets help, but are NOT infallible.
You need to be going about 10-15 MPH over the coil -- not an easy task as you need to stop at the light and the coil might be too close. The height of the magnet is important as it should be close to the road surface. Depending on how it's mounted the magnetic field MAY concentrate itself in the ferrous metal frame and not extend far enough toward the road surface to be effective. Ideally, it should be mounted away from a steel or iron metal, perhaps on an aluminum surface. Since these magnets usually come with tie wraps the tendency is to fasten them to the frame instead of mounting them on the bottom of the motor where they could be more effective. More effective that is if you rode the center of the motorcycle over the edge of the imbedded coil.
One trick I've tried with limited success is to stop with the left side of my bike over the coil and put the sidestand down. One problem with that on my Suzuki Bandit is you need to be in neutral lest you kill the motor. This technique doesn't always work but it seems to be more than 50% effective.
Good luck -- maybe checking with the governing body tht maintains the signal would get an engineer to at least look at the problem, maybe switching out several sealed modules to see which might work to detect a motorcycle or even a bicycle.
I'm not at all sure that this type of signal is universal, but I'm pretty sure the older, weight sensitive signals are long gone and most are of the type described above. The city engineer I met said MInneapolis never used the weight sensitive unit as they weren't reliable in very cold weather -- makes sense to me.
Topic: reporting traffic lights that won't change to green (Read 5512 times)