Some vehicles defy easy classification. Take the plug-in electric Peraves E-Tracer, winner of the 2010 Automotive X Prize Alternative Class. Balanced on two wheels and operated with a throttle, it's similar to a motorcyle. But it's also fully enclosed in a Kevlar fiberglass shell. It has two bucket seats, a floor-mounted brake, windows, even a windshield wiper, making its interior feel more like a car... Read about my test drive of the E-Tracer in the Los Angeles Times, Nov. 13, 2010.