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Currently, states that are out of compliance with the National Ambient Air Quality Standards must, according to the Clean Air Act Amendments of 1990 (CAAA), develop and implement control strategies that demonstrate specific degrees of reduction in emissions-with the degree of reduction depending upon the severity of the problem. One tool that has been developed to aid regulators in both deciding an appropriate course of action and to demonstrate the desired reductions in mobile emissions is EPA's Mobile 5a emission estimation model. In our study, Mobile 5a has been used to examine the effects of regulatory strategies, as applied to the Northeast United States, on vehicle emissions under worst-case ozone-forming conditions.

Growing social and regulatory pressures are compelling automakers to make cars with not only higher quality but also lower lifecycle environmental impacts. Examples include rules and incentives for clean manufacturing, low-emission vehicles, and recycling. Yet focusing on any single issue or stage of the car's lifecycle in isolation can easily turn into a zero-sum game: any improvement in one area can worsen other issues or stages, or even render the car unmarketable or unprofitable. This paper describes a system-level approach to car design that could minimize lifecycle environmental impacts without sacrificing the features that make cars attractive to consumers, such as price, performance, safety, comfort, and styling. This approach is the ultralight, hybrid-electric “hypercar” concept developed at Rocky Mountain Institute's Hypercar Center since 1991.

A model for calculating the residual gas fraction in spark ignition engines has been formulated. The model accounts explicitly for the contribution due to the back flow of exhaust gas to the cylinder during the valve overlap period. The model has been calibrated with in-cylinder hydrocarbon measurements at different values of intake pressure, engine speed, and valve overlap timings.