13 Feb 2007
Interface Puzzler #1 Answer
Thanks to everyone who wrote in and gave solutions to the first Humanized Puzzler. There have been many more responses that we anticipated! I loved the discussion of the problem. Although I had meant for people to email the solutions privately instead of discussing publicly, in retrospect, the discussion was more valuable than the secrecy. The next puzzler will all be discussion.
In short, the puzzler asked, “Can you design a car that isn’t forward/reverse modal?” For those who didn’t read the original post, check out the full question.
Few people were fooled by my implication that a solution was impossible. With modern automatic cars, almost any conceivable behavior is possible for shifting because the gear selector is simply an electronic switch physically decoupled from the transmission. The trick is choosing a good behavior.
Here’s an overview of some of the refreshingly varied solutions.
Rather than having a gear selector and two pedals, there would be only two pedals: one for forward; and one for reverse. The car is assumed to have an automatic gearbox.
Pressing the pedal for the opposite direction, or both pedals together would act as the brake. Touching neither would mean that the car continues to coast, in the same way that cars do now. We would assume that the driver gets enough feedback from the motion of the car that she can determine which direction the car is moving in, at any point in time. — John SutherlandThis is an inventive solution, one that hadn’t occurred to us at Humanized. It solves the problem handily. On the other hand, to use it properly would require more than a modicum of retraining. This presents a rather large hurdle: marketing it would be as hard as selling basashi to a vegan.
Another problem arises: there are many inputs that give the same output. Because the speed of acceleration and braking is determined by the relative position of the two pedals, moving the pedals in tandem yields many positions for the same amount of accelerating/braking. Much more importantly, having both pedals act as brake requires much more dexterity than a single pedal (and introduces accessibility issues). And, a great deal of care would have to be taken when releasing the two pedals, otherwise the car would go skittering off accidentally.
All in all, an inventive but probably not practical solution.
I have one suggestion: a quasimodal steering wheel. Two opposite portions of the steering wheel could be [pulled] back, or have two buttons that need to be pushed to make the car go backwards. — PianohackerThis is a slightly more elaborate version of the the simplest solution to the modality problem: a single button that, while held, causes the car to move backwards when gas is applied via the standard pedal. Once the car is rolling backwards, there is no need for the button to continue being pressed.
Why doesn’t this constitute a mode? We’ve created a state where, after the car is in reverse and the button has been released, there is no direct kinesthetic feedback. Shouldn’t it be considered a mode? Jef’s The Humane Interface has the answer:
Modes are, in a first approximation, situations where a particular gesture is given different interpretations when the system being used is in different states. When you are unaware of system state (i.e . your locus of attention is not the system state) your use of a gesture may have an unintended effect. This is a mode error. After consciously putting the car into reverse, your locus of attention is on the system state: you are actively driving the car backwards. The system state is guaranteed to be your locus of attention because of the quasimodal entry and then your subsequent concentration on the act of driving.
This solution obviates the need for a “Reverse” entry on the gear-shift.
The two-button coincidence proposed by Pianohacker is a bit overkill. The only time reverse is needed is when the car is already stopped, and it is enough for one button to be pushed. And Henry Blum pointed out a problem with even a single quasimode button:
If this button is on the wheel (rather than on a stick shifter behind the wheel seen on some automatics, or some other location) then you come across the difficulty of holding the button while turning the wheel around.Pianohacker, however, had a solution. He mentioned that the steering wheel could be pulled back to engage the reverse quasimode. It can be used with one hand or two hands, and doesn’t keep (or force) the driver from turning to look back. It’s a nice natural mapping that would yield a wonderful feel to reversing. And, to top it off, it would be faster to use than a gear-shift. I could easily see this solution catching on in sportier cars.
Ever since I was a teenager struggling to learn to drive, I have always wished for a car which you controlled with a self-centering analog joystick. Just push with varying pressure to go faster in any direction. Centering the joystick stops.
In fact, I never really got the hang of it, and now I only ride motorcycles. I never realized that it’s because other than the gear shift (which on a motorcycle with no reverse gear, are all really sub-selections of the same mode), there are no modes! — David Young
Like David, I have also always wished for a joystick control for my car. Push forward to go forward. Pull back to slow down and stop. Release the stick and pull back again puts the car into reverse (this way you can stop without worrying about accelerating into the car behind you). Left and right turns left and right. Learning would be almost instantaneous: the control scheme is an elegant natural mapping. No need to shift the seat far forward for those of blessed with shortness, or far back for those cursed with long legs. To top it off, it allows for sleekly clean design of the cabin as well as the removal of the steering column (one of the more dangerous parts of the cabin).
Andrew Clarke makes a valid complaint:
One of the reasons the accelerator in a car is at the driver’s feet is that it’s by far the safest place for it. If you’ve ever driven with a small dog and it jumped down under your legs while you were moving at 60 mph, just remember the sudden panic you felt. At that moment you realize that little alcove is sacred. Bringing that space further up into the cabin allows for a whole new array of potential disasters. When the difference between 10 mph and 100 mph is a slight amount of pressure, you simply can’t allow anything near that accelerator but the body part you use to control it.
Safety comes first. But the current car control scheme already has serious drawbacks: anyone who has had a fast-food drink roll underneath their feet knows that the foot-alcove isn’t as safe as it could be. It’s hard to fix, but with a joystick a simple clear protective dome with a hand-entry port would do the trick.
Unfortunately, this is radical enough that it will probably not get adopted any time soon. But for now, as Darrel pointed out, you can see it and an omni-directional driving system here. Its complicated behavior is controlled with a simple joystick.
Head Turn Interface
A couple people gave solutions that involved using a swivel chair to have the car simply go in the direction you are facing. The solution, while imaginative, is not practical without a major redesign of cars. And even then, unless the swivel was very quick (which might be physically discomforting) it would be a laborious process to do the forward-backward-forward dance of parallel park.
If you’re in neutral and you hit the gas pedal while looking backwards, you go backwards. If you were looking forward, then you go forward. Once you’re in motion, the direction you look has no effect. — Paul Ingemi Although Paul said the example is modal, it isn’t: the kinesthetic feedback of looking means that you will be conscious of the system state. In particular, it will be the same state as your head direction.
This would be a marketable solution, but like many marketable solutions, it has some inhibitive problems. First, when parallel parking, it would be trying to constantly shift your head. Second, where you are looking is not always consciously controllable: a flash, loud noise, or other stimulus can cause you to involuntary your head towards the source. Third, you may not want to look at something else (like an approaching car) while you begin reversing. An interface that is too clever often does the wrong thing. An interface that is too clever can be quite dumb.
Keep the steering wheel. But change the gas [pedal] to swivel in forward and reverse (like a teeter totter). Tilt it forward to go forward. Reverse to go reverse. Have two gears (Park and Go). Keep the break peddle too. I had a Toro riding lawnmower like this once and it was great. — David JustThis is a good solution. Pianohacker mentioned that he, “[remembers] something like [that] from a human factors class [he] took in design school. They [said] that the gas pedal sometimes is confused with the break pedal, especially with elders. A solution was one pedal; tilting forward (your toes) moved the car forward, tilting it back (your heel) was the brake.”
Eddie was quick to give an ergonomic counter. He asked, what “about the ’sudden reverse’ that could spring up with a teeter?”. Andrew Clarke drove the point home, “The tilting gas pedal model has a …problem. Unless you’re a woman used to wearing high heels, pushing the pedal down at a forward angle would be agony on a long trip. Currently the weight of your leg does all the work. Anything that doesn’t allow the driver to relax for most of the trip decreases enjoyment and increases fatigue and risk.”
These problems are not insurmountable. With enough testing and tweaking, a bet a good ergonomic compromise could be reached.
Roy Osherove proposed my favorite solution. It solves the accidental rocking problem, the fatigue problem, and the retraining problem. Unfortunately, it was after the deadline.
In this solution, the brake pedal remains the same, and the acceleration pedal remains mostly the same. Pressing down causes the car to go forward, but hooking your foot underneath the pedal and pulling causes the car to go backward. Natural mapping is retained while not breaking current habits. No new controls or buttons are needed, there are no new edge cases to deal with, its as fast as a gear-shift to use (or even faster), and can be explained in an instant. On top of that, reverse will never accidentally get engaged. It’s the sort of evolutionary change that might actually get adopted.
A couple people proposed adding an extra, smaller pedal that just accelerates backwards. While this certainly works, I think a push-pull pedal is a more elegant solution to the problem. Push-pull is naturally mapped and doesn’t add extra clutter to the cab.
Going over all of the solutions, it is very hard to figure out to whom we should send the dubious honor of a Humanized shirt. David Young gave an excellent description of the wonderful joystick solution, so he is the winner of the Humanized Puzzler #1!
Thanks again for everyone that took part in the puzzler. Puzzler #2 will be out soon, so stay tuned.
by Aza Raskin