is the gas cap door on a friend's car. Can you
guess how to open it? The first time my friend
went to put gas in his car he spent about
half an hour at the gas station trying
to figure out how to open his gas cap door! He
looked everywhere for some knob to pull to
release the gas cap door. He looked
under the dashboard, in the
glove box, behind the seats, in the trunk.
To no avail. The gas station attendant didn't
know how to open it either. Finally
someone drove in to get gas who knew the secret.
You just push in on one edge of the gas cap door,
and it swivels open! Wow, it only took 1/2 hour
to figure out how to do something that should have
been immediately obvious!
design is bad because there is no visible
control for opening the gas cap door. For example,
putting a small raised non-slip surface on the
to-be-pushed edge of the door might make it more
likely that people would expect to push it. Putting
a small lip on the opposite edge might make it more
likely that people would expect to pull it.