Tuesday January 24, 2006

The Case of The Perplexing Pump.

I’ve run across this interface design issue twice in the recent past, and it confused me both times. I took my camera back to the gas station the third time, just to document the interface behavior. How’s that for following through?

The Crime

So I was at the Shell station this weekend, filling up my tank (Fig. 1). I finished filling up, returned the nozzle to the pump, and approached the screen to finish my transaction. The first question on the screen was “Would you like a car wash?” There were “Yes” and “No” options onscreen, and each was tied to a grey button off to the side of the screen—much like an ATM interface (Fig. 2). “No” was attached to the third button down on the left, and “Yes” was tied to the fourth button down on the left. I pressed “No” to answer the car wash question. The next question was “Reciept?” I made sure to pay attention to the order of the answers, because this is where I remember it got tricky. My attention paid off because, sure enough, the “Yes” and “No” options switched positions (Fig. 3)!

The Motive

What’s the deal there? Did they do some extensive user research and find that customers who categorically select “No” for car wash select “Yes” for receipt? Or that customers who always select “Yes” for car wash never want a receipt? Were they trying to save me the trouble of moving my finger half an inch to select “Yes” for my receipt?

The Verdict

It’s not a good idea to change an interface protocol once it’s been established. Deviations from expected behavior confuse the flow of the experience, even on something as basic as a gas pump.


Brian » 5660 days ago #

No, they’re trying to get you to acidentally agree to pay for a $5 car wash.

Jared Christensen » 5660 days ago #

Interesting theory, except that the car wash question comes before the receipt question, not after it. And it is the receipt question that breaks the convention, so… they’re trying to trick you into getting a receipt?

jason » 5659 days ago #

that’s retarded. would make at least sleezy sense to put the receipt first and trick you into getting a car wash, like a web signup form that pre-checks the “i want spam” questions even when you go back to edit.

will people learn? are we fighting a losing battle? why are so many people retarded?

Pierce » 5659 days ago #

I don’t know who does these ATM screens. There are always glaring usability issues.

Do you also find that when you have an isolated one or two options available from the four buttons down the side of the screen, sometimes the angle and depth of screen in the glass causes a parallax problem so you can’t tell if it’s the second and third button, or the third and fourth that are your options? Head weaving ensues.

My other major gripe (at least with the Bank of Ireland ATMs) is when you request your balance on screen, you get across the centre of the screen the “balance: XXX” and above it asks you if you require and more services and below it gives you the yes or no option. No matter how often I use it I end up staring at that screen in confusion for a couple of seconds.

“Balance is 200 euro, yes or no?” Huh?

ATMs, gah.

Richard » 5659 days ago #

Ahaha, nice.

I’m with pierce on the usability issues, particularly on ATMs, the depth of the screen and viewing angle always leaves it unclear exactly what button should be pressed.

Dan » 5659 days ago #

I’ve run into this same issue at a gas station near my house. My theory is similar to the one above. By giving you the car wash question first, they are counting on people thinking it will be a receipt question, and that they will quickly press “Yes” without reading the screen. I’ve come close a couple times myself. But then, the issue with reversing the corresponding buttons makes no sense to me at all.

Erik Mallinson » 5659 days ago #

I hate the UI on ATMs. Back in the day a majority of them could be controlled via the keypad, with enter/cancel being the equivalent of yes/no. I got used to that but it’s not a feature in most ATMs I’ve used lately.

I also hate when the gas pump asks you if you want a reciept but it’s unaware that it’s out of paper.

James Mathias » 5657 days ago #


The “no” answer for cash wash comes first in the list of choices as it’s the most common answer. “Yes” comes first in the list of choices for receipt as it’s the most common answer.

Although I can see the thinking of the programmer/developer of the machine, I do agree that it is confusing and does break the flow and convention.

Lastly, I think it’s a good real world lesson that “reading before doing” is always good, never bad.

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