Chevrolet VoltClick to enlarge picture

The Chevrolet Volt plug-in hybrid concept represents just one of the new hybrid systems on the horizon.

In 2004 when MSN Autos first published "What Is a Hybrid?," car buyers were struggling to understand concepts like electric motors helping a gasoline engine and regenerative braking. Then, there were just six hybrid models offered: the two-seat Honda Insight; two compact sedans, the Toyota Prius and Honda Civic Hybrid; Ford's small Escape Hybrid SUV; and the Chevrolet Silverado Hybrid/GMC Sierra Hybrid full-size pickups.

By the end of 2008 there will be 20 hybrid models available, including a full-size pickup, full-size sport-utility vehicles and an ultra-luxury sedan priced north of six figures. But just as drivers are beginning to become comfortable with the technology, the long lineup of experimental and prototype hybrid systems being developed four years ago are ready, or nearly ready, for prime time—including three that use no electricity.

Message Board: Are hybrids the best way to deal with rising fuel prices? Voice your opinion!

Regardless of a hybrid system's design, each combines two sources of power to achieve the same results in varying degrees, increase fuel economy and reduce harmful emissions. Here's a look at the emerging hybrid vehicle technologies.

Two-Mode Hybrid: What Is It?
It's a system many people may not have heard about, but its design could make a substantial impact on the hybridization of the automobile.

Hydraulic: A Hybrid for the Big Dogs
Heavy vehicles that operate in constant stop-and-go driving would see huge benefits.

Plug-In Hybrids: Return of the Electric Car?
Advances in battery technology would allow commutes of 40 miles or less to be made entirely on electricity.

V2G Technology on Plug-In Electric Vehicles
The vehicle's battery can also be used to power homes and businesses.

A Zero-Pollution Air-Powered Car
It's not just a bunch of hot air. The air car will hit the streets of India in 2008.

Steam Engine Technology in the German Driving Machine
BMW is using the same principle from more than 100 years ago to improve fuel-efficiency.

While hybrid vehicles haven't exactly swept the automotive world, it's clear they have muscled their way into consumer acceptance and have grabbed the attention of automakers. It's also clear that electricity in the drivetrain isn't the only way to hybridize a vehicle.

Larry E. Hall is editor of Northwest Auto News Service and a freelance automotive journalist based in Olympia, Wash. He has an intense interest in future automotive technology.

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