Jim Moylan died recently. He was the Ford engineer who proposed that little arrow on the fuel gauge of most cars that indicates the cap’s location. It’s handy when you’re pulling into a gas station to refuel, especially when you’re driving an unfamiliar car.
The Moylan arrow is such an obviously useful idea that it was immediately implemented by Ford and widely adopted by other manufacturers. It’s also an excellent example of good information architecture — and one that provides important lessons as we navigate the AI age.
How Is This Information Architecture?
Information allows us to act more skillfully. Imagine you come to a fork on a road. Without a sign, you’d need a compass or a great sense of direction to choose correctly. But with a clear sign, you’d quickly know which road to take. The sign reduces ambiguity.
The Moylan arrow, too, disambiguates a choice. Pulling in on the wrong side of the pump is an annoying inconvenience. By making the driver smarter, the arrow improves the car’s UX. Critically, it does so without much cost to the manufacturer. That’s why it’s become pervasive.
“But,” you may protest, “this isn’t IA; it’s user interface/icon design.” That’s partly true. As usual, users experience IA in an interface. The arrow wouldn’t be as effective if it wasn’t clear and recognizable. Visuals — the choice of symbols (an abstracted gas pump and a triangle) and colors (usually white on black) — are key.
But there’s more to it than that. A big part of the arrow’s effectiveness is its location: on the dashboard, next to the fuel gauge — exactly where you’re looking when your car needs refueling. Consider how much less effective it’d be if it were only noted in the owner’s manual.
The Moylan arrow works because it’s:
- Clear: legible and understandable
- Findable: located where you’re already looking
- Relevant: provides the exact answer you need
- Contextual: available when needed, but “quiet” otherwise
- Obvious: doesn’t need further instructions
- Cheap: of negligible cost to manufacturers
The arrow isn’t just a clear icon. It disambiguates a key structural distinction of the car. The mental model is clear: most current ICE cars have their fuel cap on either the left or right side. The question is, “which is it for this car?” The answer is obvious once you know where to look — and it’s cognitively respectful (i.e., it doesn’t scream, “LOOK AT ME!” while you’re driving.)
Which is to say, the Moylan arrow: