Non-Modal Car

    Aza Raskin (son of Jef Raskin, creator of the Apple Macintosh), posted the following puzzle over at Humanized.com:
    http://www.humanized.com/weblog/2006/12/15/humanized_interface_puzzler/

    An interface has modes if one gesture can mean different things, depending system state. Modes are at fault when you miss a call because your phones in silent mode. And there's little worse than having the final bars of Appalachian Spring – with harmonies as delicate as frozen cobwebs – thrashed by a cellphone who's owner has forgot to put it into silent mode. Perhaps there is something worse: having it be your cellphone. You can read all about modes, modes errors, catastrophic mistakes, and some solutions in our article Visual Feedback: Why Modes Kill.

    This is the challenge:
    Is it possible to design a car that isn't forward/reverse modal? If it isn't possible, why? And if it is possible, how?

    What he's asking is, can we make a car that can reverse or go forward, but NOT USE THE SAME PEDAL TO DO BOTH. Using the same pedal for both leads to all kinds of problems for us humans.

    Anyway, I went to post my answer, but their comment system wouldn't let me, so here it is for you:

    Make the steering wheel control acceleration and deceleration. As it is pushed/tilted forwards, it accelerates the car. As it is pulled/tilted backwards, it decelerates the car. Deceleration is understood to be the same as thrust in the rearward direction, and so reverses the car when applied enough.

    I don't think this would be modal, because it coincides with a fairly common mental model. However, if it would be, then this clarification should fix it.

    Make a stick similar to a gear shift, positioned to the right of the driver. There are three positions: forward, centered, and backwards.

    Pushing the stick forward accelerates the car to a degree proportional to its forward position. Pulling it back towards the center slows it down to a stop. Pulling it back past the center towards the back of the car reverses.

    If needed in order to prevent accidental damage, there can be a button on the handle that must be pressed before the stick can go into the reverse position.

    Either way, this is not modal because the stick's position ALWAYS correlates to the same action of the car.

    -micah

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