This makes me wonder if anyone has thought to add microphones yet to the array of sensors an autonomous car uses. Things like "my neighbors alarm keeps going off when I go into reverse" and "there is an ambulance somewhere I cannot see yet" sound mighty useful (well, at least the latter example), but very hard to incorporate.

I like this idea too, along with also adding a network so that the cars could all communicate to each other. I have always found horns and turn-signals to be lacking in the amount that can be communicated to other drivers.

The problem with an inter-city highway is that you would have to require every car driving on it to be able to recognize and interact with those sensors. That would be decidedly unfair to those who cannot afford to upgrade their car to go on that road.

So that does bring up an interesting question though, when and where are we going to have roads where only autonomous vehicles are allowed?