User Friendly: How the Hidden Rules of Design Are Changing the Way We Live, Work, and Play

by Cliff Kuang

There are three things an autonomous car has to get right, plus one: Above all, we need to know what mode a car is in, whether it’s driving itself or not. That harks to probably the oldest axiom in interface design—mode confusion causes most airplane crashes. Alfonse Chapanis and Paul Fitts were the first to discover it when they studied World War II pilots who’d engaged the wing flaps instead of the landing gear. The second principle Lathrop calls the coffee-spilling principle: For us not to get surprised, then freaked out by a driverless car, we need to know what it is going to do before it’s actually done. Third, and perhaps most vital in fostering trust, is that we need to know what the car is seeing. And finally—the “plus one” in Lathrop’s formulation, because it relates not just to the user but to the interaction between user and machine—we need perfectly clear transitions when a car takes control, or when we take control from a car.