Every motorcyclist knows them: those traffic lights that remain red until a car or truck triggers a green phase. They have sensors embedded in the road surface - you can usually see them as circles or octagons covered in tar. The idea is that it's pointless to turn a light green unless there is actually someone on the road to take advantage of that green.
Well, my sense is that those sensors are relatively old - I'd say from the 80s and maybe 90s. I guess at the time, they seemed a good idea. Nowadays, though, two-wheeled traffic is increasing and these sensors cause real problems.
Cyclists do mostly fine, since they can step off and push the pedestrian buttons on the side of the road. That solution is not perfect, of course, since it requires one to get off the road onto the sidewalk. Also, this doesn't work where pedestrian traffic doesn't go the way of road traffic. For instance, if the cyclist wants to turn left, instead of waiting for a green on the left arrow, (s)he may have to cross the intersection in two tries.
For motorcyclists, the problem is much bigger. First, we cannot simply leave the bike on the road while we push a button, nor can we ride the bike onto the sidewalk. Second, walking the bike across the pedestrian walkway is just not feasible.