A project that retrofits a GM/Vehma electric G-Van with valve-regulated lead acid batteries and a natural gas power unit is described. The goal of the project is to develop a control strategy and system to minimize both the emissions and the costs of operation of the hybrid vehicle.The conceptual development of a control system for a light-duty fleet vehicle is presented. Control requirements of a series hybrid propulsion system are discussed based upon the analysis of factors affecting its operation. Specifically, the effects of the duty cycle are investigated in detail. A concept of a control system is introduced and modeled using MATLAB/Simulink software. The model input is validated by monitored trials of the vehicle. Various control strategy options are evaluated for typical operating conditions.The projected vehicle emission are estimated by simulation. The quantities of ground level emissions are presented for various urban routes in Vancouver.