I read an article once that said automobile designers wanted to get rid of plates altogether. It seems they limit design possibilities.

They suggested transponders in each car that would give the ID to a police officer if he pointed a "gun," similar to a radar gun, at it. They said that other possibilities included readouts of speed, exhaust emissions, etc.

While it was doing all of this it could check to see if the car was on a stolen list, or had outstanding traffic warrents. Also within the realm of possibility was a button on the gun that would turn off your ignition and leave you sitting until they could write you a ticket if you needed one.

They failed to mention Big Brother, civil rights, privacy, the fifth amendment, and how you could identify a hit-and-run vehicle if you weren't a cop. Maybe these little imperfections are what kept it from becoming a reality.
Howard