One of the usual complaints about electric cars is how you handle long road trips. If an electric vehicle has a range of just a couple hundred miles, and then requires eight hours plugged into the wall.

But what if you could charge your car while you were on the road? That's the idea behind Germany's IAV Automotive Engineering, which has patented a system that embeds charging electronics right into the roadway, juicing up cars as they merrily roll along.

The idea is similar to any number of wireless power innovations: Electromagnetic field generators embedded in the road would induce an electrical current in charging equipment on the underside of your car, which would charge your battery as you drive. The chargers would activate only when a vehicle is present, using an RFID tag to identify the vehicle to the charging system (in part, presumably, to bill you appropriately for power used).

IAV says the system currently works at 90 percent efficiency and would be ready for commercial rollout in about three years. Similar systems could also be adapted for home use while cars are parked: Wireless chargers could be installed in your garage, for example, freeing you from the hassle of having to remember to plug your car into wall power after a long slog home from the industrial park. Nissan has a garage-based charging system in the works, as well.

Naturally there's a bit of a problem with the idea, and that's the little matter of how you outfit a highway system as vast as America's with what sounds like relatively complicated charging equipment. The U.S. has over 46,000 miles of interstate highways alone. Adding charging circuitry to all that roadway would surely cost tens of billions of dollars or more -- and that doesn't even consider adding equipment to intrastate roads.

Still, great idea... at least in theory.