The classic example
The two-hand operation device is perhaps the most used example in security class and machine design.
Incidentally, it’s also one of the worse. The first designs were simply made of two separated buttons.
The average human, being more clever than some elitists might like, found a way around it: simply take a piece of wood and you are able to press the two buttons simultaneously with a single hand.
Oh, but engineers can do better! They improved the design by adding a little “shelter” to the buttons, as you can see on the next picture. This way, there’s no easy contraption enabling you to activate the device with a single hand.
Solving to wrong problem
The problem here is that a dangerous machine could cut/crush/rip/ the hands of a careless operator. I don’t say it meanly, we all are somewhat careless eventually. The solution is to add some security device to the machine. The two-hand operation takes the wrong approach, by requiring the operator to use a superfluous hand. This is the equivalent of requiring the operator to dance the Swan Lake before using the machine in order to be sure he is swift enough to react quickly. Here are two simple rules if you ever need to design somewhat dangerous machines:
- The machine should not require the operator to be alert/attentive/whatever
- The machine should not handicap the operator to avoid rule number 1.
What’s the harm?
“But it’s simply pressing two little buttons, there’s no harm!”
Really? What about a one handed man? Or even someone without arms?
The human mind was able to create a machine that could work for anyone, giving an opportunity to a one handed man he would never had in a savage land. Technology helps people. Yet, because engineers were lazy, countless machines now require a two-handed operation. This is a gigantic fuck you to anyone who can’t use two hands simultaneously. “Yeah, you could have used this machine as well as anybody else… but I would have had to think a little harder. Sorry dude.”
By installing a two-handed control, you are openly saying you don’t care about those individuals. And you are lazy. And I hate you.