This is the product of a daydream on a road trip to my parent's place over the weekend.
Once radio frequency identification  chips are cheap enough to throw away with a cereal box, they could be embedded in roads, maybe as part of the line painting process. Like pheromones for ants they could tell the car where the road is. The RFIDs might need to be mapped and inventoried while the lines are painted. The paint truck could use a combination of GPS and wireless networking to record the coordinates of each RFID as they are laid into the road. There would probably need to be a certain density of IDs to account for individual unit failures over time.
The cars would periodically ping the RFIDs and correlate those with built-in GPS and a local cache of the RFID-GPS database and adjust its course and velocity as appropriate for the approaching turns and hills. Cars would probably need to have RFIDs or some other wireless tag so each car would know where other cars were.
Obviously this doesn't solve the whole problem. Colorado Highway 6 occasionally gets closed in the winter because of avalanches. The degree of wetness and temperature of snow radically changes road conditions. Perhaps more important, the type of tires and amount of wear hugely influences traction in even modest weather. Weather might also interfere with the wireless communications. Deer and foxes and raccoons don't generally come equipped with RFIDs, but are known to cross paths with automobiles. Potholes or miscellaneous road debris probably wouldn't show up in the database. And the snowplows clearing the roads in winter, or spreading sand or deicing liquids could trash the network of RFIDs. In short, reality is radically messier than a pleasant geeky daydream. But it hints at the kinds of cool things that we haven't seen yet and seemed worth blogging.
Of course, the most important part is that people probably don't want cars that steer themselves. For example, it would take all the fun out of sports cars.
 My wife, Sarah, suggests that acronyms should be banned. If people were forced to actually speak the words instead of the initials or acronyms, we might end up with sensible names for things.
 Of course tagged cars opens the privacy can-o-worms, too.