More expressive cars

When it comes to communication with other drivers and with pedestrians, motorists have only a couple of bits available to them (the horn, flashing the high beams, gesturing, etc.) There have been times when I was waiting to cross the street on foot and the driver of the car at the intersection would beep their horn, leading me to wonder "Does that mean that I should cross, or that I should not cross?" One solution would be a car-mounted public address system, such as one sometimes encounters around Election Day, but this would likely invite abuse and a backlash from the community at large who do not wish to hear what's on one's mind.

Instead, why not have a set of LED text displays mounted on the vehicle to show some text messages? With a button press or two, with voice feedback to the operator, the signs could display things like GO AHEAD or STOP or EMERGENCY! or YOU ARE DRAGGING SOMETHING BEHIND YOU. If we make the text standard and pre-recorded in nature, it reduces the temptation to the driver to be typing in traffic, and would discourage those who might want to scroll up something along the lines of HEY BABY ARE YOU FREE???

I seem to think that something like this was done before, but was only a rear-window display suitable for communication with tailgaters, and that it didn't really catch on. I would want at least two displays viewable from the front and the rear, with a choice as to which one would display the message I select.