Hybrid electric transit vehicles offer many improvements over conventional diesel fueled buses through the application of new and emerging technologies not previously applied to the bus environment. However, these changes require the manufacturers of hybrid buses to go to great lengths to insure that the industry does not take a step backwards and end up burdened with unreliable vehicles which do not perform as advertised. This paper will describe Nova BUS's approach to developing a reliable hybrid electric transit bus through a comprehensive test and evaluation process. The substantial changes in technologies, drive train configurations and potential failure modes inherent in the design of hybrid vehicles require a fresh look at the way bus designs are tested and validated. The ultimate goal of this process is to provide a quality product to the market which offers the full range of advantages which are possible using hybrid technology. These advantages include improved fuel economy, reduced emissions, and better reliability.