For the last part: If the cars, for the most part, actually are able to read signs (which they should), the RFID would serve as additional security. And in thi

For the last part: If the cars, for the most part, actually are able to read signs (which they should), the RFID would serve as additional security. And in this case, any discrepancy would be reported back by any car passing by, so the error could be corrected quickly.