The Toyota Prius first emerged as a concept car in the mid-1990s after the company spent two decades experimenting with cars operated by electricity and gasoline power together [source: Taylor]. The production version went on sale in Japan in 1997 and was the world's first mass-produced hybrid car. As a hybrid, it used a battery and an electric motor coupled with a small gasoline engine to achieve low emissions and strong fuel economy -- in fact, the first-generation Prius managed about 66 miles per gallon (28.1 kilometers per liter) [source: ToyoLand]. The Prius went on sale in the United States in 2000 as a 2001 model, and with some added horsepower it was rated at 52 miles per gallon (22.1 kilometers per liter) in the city and 45 miles per gallon (19.1 kilometers per liter) on the highway. This Prius, however, never saw the strong sales of its successors, perhaps because of low gas prices at the time and its small body -- the original Prius design was a subcompact not much bigger than a Toyota Echo sedan.
In 2003, Toyota upped its game with the second-generation Prius. This is the Prius model that's so common on the roads now. The U.S. sales numbers for the Prius doubled the year the second-generation went on sale [source: Taylor]. It grew in size, becoming a larger five-door hatchback model, better able to meet the needs of families. And it also sported a completely new hybrid powertrain that Toyota called Hybrid Synergy Drive, which included a smaller but higher voltage battery, a more powerful electric generator, and greater fuel economy [source: Toyota Motor Corporation]. The car also featured a unique teardrop shape designed to maximize fuel economy through aerodynamics. Even though it was faster and larger, the Prius now managed 60 miles per gallon (25.5 kilometers per liter) in the city and 51 miles per gallon (21.7 kilometers per liter) on the highway. This was later revised to 48 miles per gallon (20.4 kilometers per liter) city and 45 miles per gallon (19.1 kilometers per liter) highway when the EPA changed their rating system in 2008 [source: HybridCars.org].
Recently, Toyota came out with an all-new Prius as a 2010 model, but you may not be able to tell at first glance. Though it looks very similar to the second-generation car, the third-generation Prius is wider and shorter. It uses a 1.8-liter four-cylinder engine instead of the car's traditional 1.5-liter engine. Using new automotive manufacturing technology, the Prius also includes several high-tech new features, including Lane Keep Assist, which warns the driver if he or she leaves the driving lane unexpectedly, and Intelligent Parking Assist, which essentially parallel parks the car for you. All you have to do is control the speed using the brake [source: Blanco]. To make the car even greener, some models even have solar panels integrated into the roof that harness sunlight to help run the air conditioning. Under the EPA's revised fuel economy standards, the third-generation Prius gets 49 city miles per gallon (20.8 kilometers per liter) and 50 highway miles per gallon (21.3 kilometers per liter) [source: Fueleconomy.gov].
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