sigh.....

[Mr. Bloom]

I've been advised that there's enough real metal on any bike. You just need to rest over the edge of the sensor. Doing this, I've never had a problem with my carbon fiber frame

[oz rider]

The most sensitive spot in the embedded loops is the centre line, so try to ride over that bit.

[OakLeaf]

I could always trigger a light with my steel bikes. There are lights that won't even trigger with an aluminum framed motorcycle sitting right on top of the loop. I have one, and while I can't off the top of my head remember this happening at any intersections where the loops were newly installed (and thus visible in the pavement), I've been doing it for decades, and I know perfectly well where the loops are. I can't tell you how many times I've been stuck at a light on my motorcycle. Sometimes both my husband on his motorcycle and I on mine aren't enough to trigger a light.

But if the magnetic induction loops CAN be set sensitive enough to pick up a bicycle chain and/or bottom bracket axle, then we should absolutely demand the sensitivity be adjusted.



ETA: more than I wanted to know about it http://www.humantransport.org/bicycl.../detection.htm

Short version: Aluminum will trigger just as well as steel (although carbon will not), but it's the configuration of the loop (which can't be easily adjusted) that's key.



Edit again: according to the article, it depends on whether it's a dipole loop or quadrupole whether there's anything at all in the center, and if the road's been paved since the loops were installed, there's no way to know which it is. With a quadrupole loop there is still sensitivity at the edge wires, it's just greater at the center - and my personal inclination would be not to stop any two-wheeled vehicle on the oil slick that's invariably in the center, if I could possibly avoid it.

[Koronin]

A year or two ago South Carolina passed a law that allows motorcycles (so I would assume bicycles as well) to turn left or go straight at a red light that cannot be triggered by the motorcycle. I don't fully remember the law, but it said you had to wait a reasonable amount of time and then may go straight or turn left if the light is not triggered.