I was driving at night in a very light rain, so I set the wipers to intermittent. Well as the misting density* changed the rate that my windshield got smeary would change, but if the interval between wipes was too small you got that sqeaking noise. When the glass accumulated too much water I would twist the nob one click up and the wipers would immediately swipe… because obviously if you want more wiping it’s because you need a wipe right now. In contrast when I turned it down a click it did not give an immediate wipe, for symmetric reasons. Someone designed that.
Also the click from one interval to the next is softer than the click that takes you from intermittent to low continuous. So you know before you cross that line. Someone designed that.
Also the knob has ridges all the way around that are a good width for my fingers. This raises questions about the statistical variation between fingers within the population as well as between men and women. Someone designed that.
This same knob also has functionality of the window sprayer and of the rear wiper and of the rear sprayer. Someone designed that.
In my othercar the windsheild wipers don’t have as cool an intermittent function, but the same lever controls the headlights, brights, and blinkers. Someone designed that.
All these designs are based on years of experiencing the world and building on the work of other designers. Someone has to decide how closely to follow in the footsteps of the preceding work and how much to branch off on their own. Even if their changes are improvements, people often prefer what they’re comfortable with over things that are new even if new is better (as Facebook is well aware).
I’d like to send good vibes out to the thousands of people that designed something I touched today.
misting density is found by taking the integral over the area of the windsheild of the cross product of the velocity of the rain (relative to the car, not the earth) and a unit vector perpendicular to the surface of the windshield at each point.