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California cars operating on higher-sulfur gasolines than prevalent in California should not result in “false tripping” of the on-board catalyst monitoring system. The monitoring systems to be used on California low-emission vehicles will be unable to detect the small extra amount of loss in catalyst effectiveness that might be caused by higher sulfur levels outside of California. Testing of a mocked-up ultra low-emission vehicle (ULEV) conducted by the California Air Resources Board (CARB) confirms that on-board monitoring systems are not tripped even by high sulfur levels (800 ppm). An independent U.S. Environmental Protection Agency (EPA) assessment also agrees that “false tripping” of monitoring systems of the California cars is not expected to be a problem either for California cars operated temporarily outside of California or for California-type cars sold in other states.

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.