Affordances, those features of a product that help you figure out how to use it, are relative.
Most of the busses in the Kitchener-Waterloo region have rear doors that open when you wave your hand in front of them. The one I took downtown this morning must have been an older model because it just had two vertical push bars on the doors.
When we arrived at the terminal, the young woman at the front of the queue to get off started to wave her hands in front of the door, which did not respond. Puzzled and alarmed, she began to shout at the driver to open the doors, until someone behind her said, “push the handle”.