> Cyclist aren't massive nor hot, on a hot summerday they will be cooler than the road surface. I think a camera with object recognition or something similar should be able to do it.

I don't know the technical details on how it's done here in Stockholm, even less in the suburbs where I've lived but it feels like magic that in some traffic lights in busier intersections they'll just trigger by themselves with enough distance that when I arrive with the bike at the intersection the lights are turning green for me.

I have looked for cameras but couldn't find them, it's even more puzzling in a specific intersection close to my house where I bike along a 4-lane road with only fields of wheat and grass, and the intersection I cross leads to an industrial area, there are only the posts for the pedestrian/bike lights and those still turn green, no cameras in sight, no detection trap on the pavement.