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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.

Emission control options for heavy-duty engines are evaluated for meeting the recently promulgated NOX and particulate standards. Particulate options to meet these standards are evaluated in terms of emissions reduction, cost, and cost effectiveness. Control options include particulate trap, clean diesel fuel (low sulfur, low arontatics), methanol, and gasoline. The cost effectiveness for particulate control range from $3,000/ton to over $18,000/ton. These costs, however, are lower than many stationary measures.