The importance of reducing NOx emissions in many urban areas has led to the development of compressed natural gas (CNG) engines for transit bus applications. These lower emission vehicles have led potential operators to question the applicability of this new technology in service. To address the concerns of transit operators, especially those with small systems, Yolo County Transit Authority (YCTA) put into service four CNG-powered BIA-Orion V buses with Cummins L10G engines. Performance data were collected for these four vehicles and four control diesel buses over an 18-month period. The results demonstrated that CNG vehicles can be successfully incorporated into small operator fleets and can perform as well as or better than their diesel counterparts.