The idea of ​​the hybrid electric vehicle (HEV) has been around for over a decade, as many people may not have initially thought. In fact, hybrid vehicles have been in development for a century. The combination of an electric motor and a gasoline engine has been a concern of scientists and inventors for many years. Hybrid cars have surpassed many feats over the years, such as increasing gas mileage and reducing pollutants released by regular internal combustion engines. Even though hybrid cars are in high demand right now, some believe these cars are just a quick fix before bigger and better ideas, such as fuel cell vehicles, begin to take over the auto industry. However, the development of the hybrid car has had many effects on society today and may continue in the future. When the 1970s arrived and the oil crisis hit, gasoline prices increased dramatically and people were very concerned about dependence on oil and petroleum. The idea of ​​hybrid cars has come back. The main financial support came from the U.S. Department of Energy, with a few automakers also putting money in. In the early 1990s, Volkswagen was the only car manufacturer considering marketing a hybrid vehicle, but only in Europe. 1993 marked a major milestone for the advancement of hybrid cars. The Department of Energy signed a five-year, $138 million development deal with General Motors and a $122 million deal with Ford to design and build pre-production hybrid prototypes that could be brought to market in less 10 years old. Four years later, a new generation of hybrid vehicles emerged with the introduction of the Toyota Prius (Sperling, p. 101). Today's hybrids come in many different varieties, such as mild or full, serial or parallel. Mild hybrids require the use of an electric motor to assist the gasoline engine when additional power is needed. It can only leave the off position if the internal combustion engine is engaged. The mild hybrid can be broken down into 3 subsystems. The Start/Stop system, also called micro-hybrid, shuts off the engine when the car is idling normally and instantly restarts the engine when pressure is applied to the accelerator. This type of system only increases fuel efficiency by about 10% and is the most basic of all hybrid vehicles..