The purpose of this study is to examine a proper power system for a miniature vehicle called as “Commuter-car” that is expected to be used for commutation or shopping in urban areas.Before starting experiments, an investigation of actual commutation driving was made. It was found that the driving distance was generally short and that start-stop frequency was high at commutation driving in urban areas. As a result of this driving investigation, it was educed to introduce an electric motor traction method into commuter-cars.First, a small generator was added to a conventional electric vehicle (EV) to convert it into a series hybrid vehicle. The running range of this vehicle was confirmed experimentally to be extended much more than the base EV in transient driving. Therefore, it was judged that series hybrid system is reasonable to be applied to commuter-cars.A simulated commuter-car of series hybrid system was set on a chassis dynamometer, and its acceleration performance and electric power-saving effect in urban driving patterns were confirmed. Also, the flow of electricity of the hybrid power system was measured, and it was found that the series hybrid vehicles can be classified into two types; “Charging-dependent type” and “Self-sustaining type” according to the capacity of the generator. These two types of commuter-cars were evaluated with respect to their merits and demerits. Further, based on this evaluation results, a method to optimize the combination of battery and generator mounted on commuter-cars was studied.