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In response to a growing need for a practical and technically valid method for measuring exhaust sound pressure levels (SPL) of on-highway motorcycles, the SAE Motorcycle Technical Steering Committee has developed Surface Vehicle Recommended Practice J28251, “Measurement of Exhaust Sound Pressure Levels of Stationary On-Highway Motorcycles,” which includes a new stationary sound test procedure and recommendations for limit values. Key goals of the development process included: minimal equipment requirements, ease of implementation by non-technical personnel, and consistency with the federal EPA requirements; in particular, vehicles compliant with the EPA requirements should not fail when assessed using J2825. Development of the recommended practice involved a comprehensive field study of 25 motorcycles and 76 different exhaust systems, ranging from relatively quiet OEM systems to unbaffled, aftermarket exhaust systems.

Carbon dioxide (CO2) is the primary greenhouse gas emitted by gasoline-powered motor vehicles, and the amount of CO2 emitted depends directly on the amount of gasoline burned by the vehicle. Any reduction in vehicle fuel consumption will also reduce CO2 emissions, and any reduction in CO2 emissions requires a reduction in fuel consumption. In 2004, pursuant to Assembly Bill (AB) 1493, the California Air Resources Board (CARB) adopted greenhouse gas emission standards for new vehicles that would require substantial reductions in CO2 emissions and fuel consumption from light-duty motor vehicles. In December 2007, Congress made significant amendments to the Corporate Average Fuel Economy (CAFE) program with the passage of the Energy Independence and Security Act of 2007 (EISA2007). After the President signed EISA2007 into law, U.S.

Concerns regarding U.S. dependence on crude oil from politically unstable regions and the impact of fuel combustion on climate change have led to new state regulations and proposed additional federal regulations requiring reductions in fossil fuel use by passenger cars and light-duty trucks. Significant reductions in fuel consumption can be achieved while maintaining the performance and size of current production vehicles; however, it does not appear that the benefits will be commensurate with the costs. Based on the same model employed by the United Nations Intergovernmental Panel on Climate Change, nationwide reductions in light-duty motor vehicle greenhouse gas emissions of 30% will have no measurable effect on ambient temperature. This calls into question the assumption that the cost of reducing greenhouse gas emissions has corresponding economic benefits related to the moderation of climate change.