The trick is to pretend you're an idiot. If the bicycle and the person on it map mostly to a rectangle of 8 squares, most people will be so stupid or hasty that they'll click that, nevermind that a human is not part of the bicycle.
The same is true with, say, buses. See an image of a delivery van? Bus! It asks you select all cars and you see no car but a vague pixel blob that someone stupid would identify as a car? Car!
One of the few things that this doesn't work with is stairs, because the side of stairs being stairs or not is something apparently no one can agree on.
