The National Information and Communications Technology Australia lab in Canberra has developed a driver's "assistant" that automatically reads speed limit signs and alerts the driver if he exceeds the posted speed. It also detects stop signs and signals an alert if the car isn't slowing down rapidly enough. Further, the system uses stereo cameras to track the driver's gaze and ensure that passing road signs have actually been seen.
Partly because it's so dangerous, the car is an excellent platform for new kinds of computer-based intelligence. We already have cars that know where they're going (GPS-based navigation systems); that can keep you from driving drunk (breathalyzer interlocks); and that can detect tailgating (short-range radar). A car that knows (and enforces) the speed limit is just a short step up from there.
What's really intriguing is the gaze analysis. Suitably enhanced, that technology might spot incipient "road rage" (caused perhaps by the knowledge that your car is staring unblinkingly at you and judging your every move) and intervene (filling the cabin with nitrous oxide, for example) before it becomes life-threatening. It could also ensure that you check your blind spot before passing and look in your rear view mirrors frequently.
Let's just hope that the designers don't try to get cute and, in the interests of customer acceptance, imbue cars with "human-like" traits--I can imagine a petulant minivan maliciously activating the air bag if I go too long without changing its oil or intoning, "I’m sorry, Dave..." when I try to pass on the right. Don't misunderstand: I think a lot of people (other than I) could benefit from this type of system; it's just that I'm afraid I may live long enough to see it become mandatory.