RFID Roads

Ok RFID is cheap and doesn't need batteries so why not embed RFID tags in roads as a guidance system. The tags would be in the middle of the lane and spaced about 2 feet apart. the car would have multiple readers on the bottom to center itself over the RFID tags and thus in the lane. The tags themselves would hold information such as the speed limit, upcoming exits or turns, how many lanes wide the highway is... basically everything we would see on a regular sign. Autodrive cars would need sonar (most minivans already have sonar on the back bumper) to avoid deer and dumb cars. They would also have WiFi to "talk" to stoplights and other cars about lane changes, speed changes etc. Easyest to implement on 400 series highways that have no stoplights. Pros: good in fog, Cons: impossible to plan for all possibilities.