The Principle of Normal Use

I've developed an idea over the years that I call The Principle of Normal Use, or, PONU for short. It's an idea I use in evaluating the quality or appropriateness of the design of something. Particularly of things you come into contact every day like furniture, appliances, tools, containers, doors, architecture, and vehicles.

The principle is that a thing should work well in normal use by a normal reasonable person. To work well it means that it shouldn't do things like leak on the floor, cut you, hit you, be too heavy or too difficult to grasp, neither too low (close to the ground/floor) or too high (out of reach by a person of average height and arm length), too hot or too cold, should have reasonable default states or forms, and so on. The list of qualities it should have is fairly long and depends on the exact thing in question. A door has certain ideal qualities that are irrelevant or don't make sense for a hand tool, and vice versa. It takes experience and a little insight to learn what works and what doesn't, what is smart and what is dumb with respect to any given category of thing, but when a thing violates PONU you will know it: you'll bang your head, get wet, slip, trip, type twice as much as you really needed to otherwise, be annoyed, exhausted or inconvenienced for no good reason and you might end up cursing it's so-called designer.

If a thing violates PONU due to a fundamental decision made during the thing's design phase, I call it a design-time PONU failure, or just DTPF or DTF.

Sometimes a thing seems to have been designed correctly, but when it came time to implement, build or install it, the people who did it made a mistake and deviated from the design. They may have done it because they were less intelligent, or weren't aware of the reasons for the original design or were rushed or chose to optimize away certain qualities in favor of reducing cost, for example. But regardless of the excuse, it causes it to violate PONU, and thus they have created a worse user experience, and worsened the human condition.

Here are some examples of everyday things that clearly violate PONU:

A pipe that leaks when water passed through it.

A computer that crashes after a few hours of simple word processing tasks. (MS Windows?)

A high-traffic public building in a cold windy city that has a single door to the outside (rather than a double-door or revolving door), and it's winter, and the door-closing-spring-mechanism thing is broken. And so every time a person passed through it a gust of cold winter air rushes into the building, hitting the poor folks sitting inside trying to stay warm, until somebody gets up and manually closes the door again. And the cycle repeats every minute or so with each new person to pass through it. (This is an example of both a design-time failure and a maintenance-time failure. But regardless it violates PONU.) There is a door in a downtown Chicago train station that's been doing this for the entire time I've lived in the area, which has been 2+ years. So clearly either the designer or maintainer of the facility is an idiot, in my judgment. It would be trivial to fix.

I believe all good ideas are eventually discovered by many people independently and so I'm sure that the principle I've described here has one or more "official" terms for it, probably in the areas of architecture or usability design. I wouldn't be surprised. But from my perspective I did develop this idea and term a long time ago, through personal observation and analysis, so I thought I'd blog about it here to share with others who may not have stumbled upon it before.