To comply with upcoming gas mileage rules, automakers will launch appealing and economical compact or subcompact cars in the U.S. market over the coming years.

But car designers are thinking far smaller yet. At the 2010 Los Angeles Auto Show two weeks ago, General Motors showed off an operating version of the two-seat, two-wheeled Electric Networked Vehicle (EN-V) it unveiled last spring in Shanghai.

Spinning in its own length

Our video (at bottom) of the EN-V being driven in a small arena shows just how maneuverable this little two-seat pod car is. It skirts the fenced edges of the small arena and spins in its own length many times. Thorughout it all, you can hear the gentle whine of the electric motor that motivates it.

The EN-V is envisioned to drive and park autonomously, especially during peak traffic periods. The secret is constant communication among vehicles, which might gain access to special traffic lanes restricted to "smart" vehicles that could understand and react to their surroundings--versus today's "dumb" cars that must be operated by actual drivers.

More than 4 billion humans in megacities

Futurists say the world may have eight billion or more humans on it by 2030, of which more than 60 percent will live in urban areas. Older and more traditional U.S. car buyers may not take to this radical new concept for a city car, but it's not aimed at them.

Rather, vehicles like the EN-V are intended for the exploding mega-cities outside North America--think Shanghai, even Sao Paulo--that simply won't have the space for 15-foot-long autos owned by 10 million residents.

2010 Cadillac Urban Luxury Concept

2010 Cadillac Urban Luxury Concept

A production version of the EN-V would likely be built from carbon fiber, Lexan, and acrylic materials. it would weigh roughly 1,000 pounds, or just one-quarter the weight of the average vehicle on U.S. roads. The vehicle's footprint is one-third that of a standard vehicle, and its two wheels allow an EN-V to rotate inside its own length.

A three-cylinder Cadillac

The EN-V sighting occurred when our Nelson Ireson attended a pre-show media event hosted by Cadillac, which showed perhaps the most unlikely Cadillac concept to date: a tiny, boxy Urban Luxury Concept hatchback just 151 inches long, fitted with a turbocharged 1.0-liter three-cylinder engine fitted with a stop-start system.

Intended to bring GM's luxury brand into a new category of small but luxurious city cars, the concept Cadillac theoretically competes with vehicles like the Mercedes-Benz A-Class and the Audi A1--neither currently offered in the States. The projected fuel economy? A whopping 56 mpg in the city and 65 mpg on the highway.

PUMA prototype

PUMA prototype

Texting better than driving

The working parts of what became the EN-V project were first seen in what was then called Project P.U.M.A. (for Personal Urban Mobility and Accessibility) back in April 2009.

Before that year's New York Auto Show, GM and Segway together unveiled a flat-black development mule sans bodywork that showed it was capable of the same quick motions and spins we see on the video of the concept EN-V.

The autonomy not only allows people-carrying pods like the EN-V to travel packed more tightly together than human reaction times would permit, it also frees the occupants to do other, more valuable things.

As GM's then-R&D chief Larry Burns pointed out, many of today's younger consumers view driving as an annoying waste of time that they could better spend ... texting.

[General Motors]