In this paper a design of a regenerative braking system for use in city buses is proposed. This system consists of a fixed displacement hydraulic pump/motor unit and a hydro-pneumatic storage accumulator which is linked to the conventional transmission of a city bus. The use of a fixed displacement hydraulic pump instead of a variable displacement pump used in existing designs allows for a very significant reduction in cost at a small sacrifice in performance. A driving pattern was constructed using data collected from actual city bus routes in the city of Madras, India. The vehicle used to model the regenerative braking system was an Ashok Leyland Comet city bus. Computer simulations show that this system has the potential of providing considerable fuel savings while significantly reducing the level of exhaust emissions.