here is the example
An emerging alternative to conventional diesel engines is the electric hybrid system. Hybrid buses typically
utilize an electric drive coupled in series or operating in parallel with a combustion engine and traction
battery.
Hybrid technology allows the use of a smaller internal combustion engine which is designed to operate near
its optimum efficiency, thereby minimizing engine emissions and maximizing fuel economy. Typically, a
hybrid system also employs regenerative braking which transforms kinetic energy into electric energy,
again improving fuel economy. To a fleet operator, hybrid technology is attractive because it does not
require the development of new refueling infrastructure or modifications to existing maintenance areas.
