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Summary:
I came across an elevator interface that was a beautiful example of an artsy design that severely handicapped the user's ability to come to a conceptual understanding of the operation of the elevator.
First, a good elevator:
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This good elevator interface was on the top floor of the parking garage of the Bob Bullock Texas state history museum in Austin, TX. It has four indicator lights. Horizontal and vertical separation help minimize ambiguity in light function. For the leftward elevator, the lights are on the left. For the rightward elevator, the lights are on the right. The top light indicates that the elevator is moving upward and the bottom light indicates that the elevator is moving downward. I was first drawn to which elevator, and then to think about its movement. The most important point is that with quick glance, the indicator lights are fairly easy to understand. What is "left-right" and what is "up-down" are indicated along visually discriminable dimensions.
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Now, a bad elevator:
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This elevator interface was the source of a bit of confusion for me. It was the public elevator inside the Texas state capitol building. The problem with this elevator becomes obvious when you attempt to use it: The mysterious quartered circle! Upon first glance, I wondered if there were any indicator lights at all (it is non-standard, and notice that the circle indicator is of similar size to the circles on the elevator doors). Upon seeing a light, a new problem arose. The horizontal and vertical separations are identical! Unfortunately, there is nothing remotely circular about the position of the elevator or its movement, so a mapping of the light shape to which elevator is being indicated or to the the function of the elevator will be misleading.
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There are two possible misinterpretations of the "bad elevator" interface: Because the up-down and left-right lights use the same physical indictors, it is logical to interpret them as having meaning that is on the same scale. 1. I interpreted all of the indicators as presenting which elevator. The light that is pictured made me think of placement to my front right, and I thought that there might be another elevator on the other side of this one that is available now (hence, on the right side and in front of me). 2. Interpreting the indicators as all movement leads to the bizarre conclusion that the elevator actually moving to the upper right. No, instead of a simple one dimensional scale, people are supposed to instantly infer a more complicated dual scaling in which horizontal is supposed to indicate which elevator and up down is supposed to indicate direction of movement. This is a big cognitive price for an artsy design, in my opinion. |
What makes the good elevator interface better than most is that is has a digital readout that allows a user to understand the state of the elevator in detail, namely its current floor and its movement. This digital readout is not perfectly unambiguous. That is okay, because it is not absolutely necessary either.
A very good elevator interface would make the current floor and movement of every elevator extremely obvious, in addition to unambiguously indicating which elevator to stand in front of. A display beside each elevator door would contain a moving diagram of its elevator. This display would externalize what floor the elevator is on and what direction it is moving. A simpler version of a moving diagram is a simple needle indicator, the same indicators that were used decades ago.
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