The utilisation of a hybrid vehicle concept enables the vehicle to be designed for specific traffic situations. Automobiles and medium to light commercial vehicles operate predominantly in suburban traffic where stop/start driving situations use large quantities of fuel because of the continuous conversion of engine power to kinetic energy and its subsequent absorption in the braking system. In addition, most vehicles operated in the suburban environment are powered by spark ignition engines. Thus energy storage or a continuously variable transmission would enable the engine to be operated at or near the peak efficiency, so increasing the fuel economy of the vehicle significantly.At the other end of the spectrum of operating conditions, i.e. highway speed driving, there is little to be gained by carrying energy storage elements on automobiles and buses. However with the advent of very low drag, articulated vehicles, energy storage on a 40 tonne semi-trailer, to help supply some potential energy for hill climbing and to absorb the kinetic energy on downhill running, is an attractive proposition.The paper describes the context in which any hybrid vehicle might have an application either to save fuel, reduce emissions, improve performance, reduce noise or improve drive-ability. The paper also describes the experience with the design of five vehicles in the Department of Mechanical Engineering, two of which have been extensively road tested and two of which are currently undergoing road tests.