John Tierney has an interesting piece on the current state of the art.

I don’t really look forward to this particular future–I like driving (though I have to confess that having a computer replace most of the other lousy drivers out there appeals to me greatly).

But my biggest concern, that I never see addressed, is reliability. Not just of the smarts in the car, but in the car itself. What happens if cars are barreling along at ninety miles an hour ten feet apart, and a tire blows? Or the brakes fail? Or the engine dies?

There simply won’t be the margin to avoid a collision, as we (generally, but not always) have at current spacing. You can make the cars as smart as you want, but physics will remain physics.