Europe has shown us three-wheel vehicles in the past. Many have been Fiats and Triumphs with one wheel fallen off. But the CLEVER concept car is intentionally three-wheeled: It's a prototype two-passenger urban vehicle that's fuel-efficient, low-pollution, and relatively safe. The CLEVER, or Compact Low Emission Vehicle for Urban Transport, is the creation of nine European research and industrial partners.

So what is the CLEVER? For starters, think "three-wheel motorcycle in a rain-proof bubble, plus safety, fuel efficiency, and low emissions." The technology behind the CLEVER is a tubular frame (aluminum, with plastic bodywork) that protects the driver and the passenger, who is seated (not straddled) immediately behind the driver. It uses a 218cc compressed natural gas (CNG) engine from Rotax, an enlarged version of the gasoline powerplant in the BMW C1—a fascinating two-wheel motorcycle-in-a-bubble that protects the driver in spills and rollovers.

The engine has a reported fuel economy of 108 mpg (2.6 liters per 100 kilometers) with a range of 125 miles or 200 km from its twin six-liter carbon fiber tanks. These are cousins to SCUBA tanks, removable in the prototype, so the tanks could go to the fuel if need be. Carbon dioxide emissions are a third less than those of traditional passenger cars, in part because the CLEVER burns less fuel. Acceleration for the CLEVER is 7 seconds from 0 to 40 mph, with a top speed of around 60 mph, or 100 kph.

Although it has three wheels, the CLEVER tilts like a motorcycle going through turns. On a motorcycle, the rider learns through trial and error how much to tilt the bike in turns, to maintain stability. The CLEVER automatically controls tilt with a microprocessor-based controller and hydraulic actuators.

The CLEVER is just 1 one meter wide, which is 20 inches narrower than the smallest ultracompact car (such as the Smart car) and 3 feet narrower than most passenger cars. That means the CLEVER is more maneuverable, and you could fit several of them into a single parking space. In a burst of optimism, a press release from the University of Bath talks about "the possibility of narrower lanes for such vehicles." Remember when Segway zealots thought they'd get special lanes?

The effort was funded by the European Union and began in 2002, with the concept car being completed this spring. Some of the partners include the University of Bath, England; the Technische Universitaet in Berlin; the Institut Francais Du Petrole in Vernaison, near Lyon, France; Institut Francais du Petrole (IFP); the Institut Fuer Verkehrswesen – Universitaet Fuer Bodenkultur, in Vienna; and Bayerische Motoren Werke AG, A.K.A. BMW.

To see other cutting-edge concept cars, click here.