Originally Posted by pgreene
triggers? I'd always assumed it was just weight rolling over the sensor implanted in the pavement, and bikes just don't weigh enough. sounds like a scam to me (unless traffic lights work in a manner with which i'm not familiar. still, find it hard to imagine something like that would work. if it's visual, does it make you huge? if it's metal, does it make you heavier?)
Many are magnetic. That is why, in days gone by and when steel ruled, a group of cyclists could often trigger a sensor a single cyclist could not. I even remember the trick (for very busy intersections) of getting off your bike and laying it on the ground across the sensor so there would be more metal surface area to detect.