These days you can pay for a taxi by credit card by making selections on a small touch-screen mounted to the back of the front seat
The vast majority of taxis have one of 2 different touch-screen UIs, and one of them has a design flaw.
After the flawed system asks you to enter your tip, it brings you to a new screen that looks like this:
If you touch “Yes”, you are taken to a screen that looks like this:
If you touch “back” you’re taken back to the tip entry screen. This makes the entire “Your total is $10.40. Is this okay?” screen superfluous — i.e., if the software just assumed the answer was “yes”, the the user would lose nothing (because he could always press “back” from the swipe screen).
And indeed the other, non-flawed, UI skips this confirmation screen:
There is a similar design flaw in Wii Tennis: when a match is over, you are asked whether you want to “Play again” or “Quit”:
If you select “Play again”, you’re asked whether you want to play 1, 3, or 5 games.
Instead, the game should give you an interface that looks like this:
Many user interfaces are flawed in this respect. For example, we’re all familiar with software that constantly asks “Are you sure?”. Don’t ask me if I’m sure! Just go ahead and do whatever it is, and give me the option to undo it if necessary. This way if I was sure I don’t waste any time, and if I wasn’t sure I lose nothing.
Gmail was basically the first web application to get this right:
As a prize for making it this far, here’s a comic example of bad design from my office kitchen:
Oh, cool, two drawers next to each other with ambiguous names. One contains something that I need all the time (forks) and the other contains stuff that’s never been used in my company’s history (ice cream scoops and spaghetti servers). Nice work FACILITIES.