HEVs are powered with a combination of a combustion engine and an electric motor. This
design, which is described in more detail in the next section, makes the HEV more energy
efficient, potentially achieving almost twice the fuel-mileage compared to conventional
vehicles and reducing tailpipe emissions substantially. Another driver for the high interest in
hybrid technology is that HEVs can act as a stepping-stone for future zero-emitting fuel cell
and electric vehicles, which will be described in section 2.3. Fuel cell vehicles and HEVs share
several critical components such as the electric motor, power controls, and high power density
batteries. By driving the cost reduction and increased performance of these components, the
continued development of HEVs will also help the development of the low and zero emission
vehicles of the future