I played for quite a while with this site, and its various captchas. The only one I got wrong was 'tick the boxes that contain traffic lights'.
One box showed only the lower half of some poles, with the button boxes for pedestrians. Might be wrong, but I'm pretty sure it was an old fashioned 'pelican' signal with pedestrian lights in among the vehicle signals, rather than a modern 'puffin' with pedestrian lights at elbow level.
So I reasoned "that's a box with a button, not a traffic light", and I left that one unticked. It seems that was the wrong answer I should have ticked it, but I still feel cheated.