I know some folks who would do well to have such a device wired to their horn circuit.

Any time people are anonymous, they are more rude and aggressive.
It happens in traffic, on the telephone, over the drive-thru intercom, and certainly and especially on the Internet.

Hmm. When someone cuts me off and then waves after I honk at them, it sure doesn't make me feel better, or that they're saying "sorry", it's more like "yeah, I drive like an idiot, but now I'm in front of you, so too bad."

brian:

Seek help.

Nah. I'm fine. The ideal purpose of a wave is to say "thank you", so that if someone wants to pull into traffic or change lanes, and I let them, it is appropriate to give a brief wave of thanks. I have perhaps bent the rules of the road for your benefit, and you acknowledge that, and civilization goes about its merry way. If you cut me off, I will interpret your wave as "thanks for letting me in" but I did no such thing, you merely broke the rules for your own benefit at my expense, and we're all the worse for it. If I could see the person's face, I might be able to better judge if they were sincerely saying "sorry" but as Michael points out, it's likely that they feel secure in their anonymity and don't really mean it.

I should think an automatically activated flashing (or neon) large middle finger would be far more useful.

It would get far more laughs, release a lot more serotonins, and be a lot less aggravating, overall (pace Brian), than having to put up with all those "Sorry" signs.

In fact, I have a hunch it will soon become standard equipment.

brian:

Your belief that you know they did it intentionally is the problem.

This kind of thing has been suggested before. Someone wanted a simple hand sign that meant the opposite of the middle finger that one could make after one had done something stupid and/or rude in public. Purely a theoretical exercise for me, of course...

OJ:

Brian is correct. Anyone spending much time in daily traffic - puttering behind a haywagon on a winding country road doesn't count - knows his statements to be true. People will cut you off and give a brief automatic "thank you" wave. A more insincere gesture was never made. It is all about context, not belief.

I'm reminded of the time I was driving down a one-way side street in Chicago. Suddenly, I realized that the car 100 yards down the street was coming at me, at speed, in reverse. As I yanked my car over to the curb, the little wave the driver gave me as she went past didn't make me feel any better.

Why stop there? Gimme a mini-keyboard and some sort of display on the side of my car, and I'll have a whole conversation. Set a few buttons to create some default sentences: "Oops! Sorry." "You go right ahead." "You cut me off, you no-good doodyhead!" It'll be great!

Either that, or make like one of Harlan Ellison's short stories and equip some good-sized guns and lasers on your car. That'll learn 'em not to go backwards on a one-way street.