A hybrid electric vehicle (HEV) is a type of hybrid vehicle and electric vehicle which combines a conventional internal combustion engine (ICE) propulsion system with an electric propulsion system. The presence of the electric powertrain is intended to achieve either better fuel economy than a conventional vehicle or better performance. There are a variety of HEV types, and the degree to which they function as EVs varies as well. The most common form of HEV is the hybrid electric car, although hybrid electric trucks (pickups and tractors) and buses also exist. Modern HEVs make use of efficiency-improving technologies such as regenerative braking, which converts the vehicle’s kinetic energy into electric energy to charge the battery, rather than wasting it as heat energy as conventional brakes do. Some varieties of HEVs use their internal combustion engine to generate electricity by spinning an electrical generator (this combination is known as a motor-generator), to either recharge their batteries or to directly power the electric drive motors. Many HEVs reduce idle emissions by shutting down the ICE at idle and restarting it when needed; this is known as a start-stop system. A hybrid-electric produces less emissions from its ICE than a comparably sized gasoline car, since an HEV’s gasoline engine is usually smaller than a comparably sized pure gasoline-burning vehicle (natural gas and propane fuels produce lower emissions) and if not used to directly drive the car, can be geared to run at maximum efficiency, further improving fuel economy. In 1901 Ferdinand Porsche developed the Lohner-Porsche Mixte Hybrid, the first gasoline-electric hybrid automobile in the world. The hybrid-electric vehicle did not become widely available until the release of the Toyota Prius in Japan in 1997, followed by the Honda Insight in 1999. While initially perceived as unnecessary due to the low cost of gasoline, worldwide increases in the price of petroleum caused many automakers to release hybrids in the late 2000s; they are now perceived as a core segment of the automotive market of the future. About 9 million hybrid electric vehicles have been sold worldwide by September 2014, led by Toyota Motor Company (TMC) with more than 7 million Lexus and Toyota hybrids sold , followed by Honda Motor Co., Ltd. with cumulative global sales of more than 1.35 million hybrids , Ford Motor Corporation with over 375 thousand hybrids sold in the United States through September 2014, and the Hyundai Group with cumulative global sales of 200 thousand hybrids , including both Hyundai Motors and Kia Motors hybrid models. , worldwide hybrid sales are led by the Toyota Prius liftback, with cumulative sales of 3.36 million units. The Prius nameplate has sold more than 4.7 million hybrids up to September 2014. Japan is the world’s largest hybrid market with over 4 million hybrid vehicles sold through December 2014, followed by the United States with more than 3.5 million automobiles and SUVs sold. The conventional Prius is the top selling hybrid car ever in both Japan and the U.S. Prius sales passed the 1 million mark in the U.S. in April 2011, and August 2011 in Japan. Japan also has the world’s highest hybrid market penetration. By 2013 the hybrid market share accounted for more than 30% of new standard passenger car sold, and about 20% new passenger vehicle sales including kei cars. The Netherlands ranks second with a hybrid market share of 4.5% of new car sales in 2012.