6. Mobile Source Mitigation Opportunities

The objective of this chapter is to review this history, focusing initially on the historical growth patterns and the resulting environmental consequences; then on the current control efforts around the world; and finally on the emerging efforts to transform vehicles and fuels to accommodate increased vehicle use while minimizing impacts on the environment. Progress in mitigating emissions of criteria air pollutants has been impressive, especially in the developed world. The situation with regard to climate change is particularly challenging. Transportation is already a large contributor to the problem and is a rapidly growing sector. Modest programs to reduce fuel consumption or greenhouse gas emissions from light duty vehicles are being phased in and California and the EU have initiated efforts to reduce the carbon content of vehicle fuels. But much more will need to be done with a likely shift to battery electric vehicles fueled by green electrons or fuel cell vehicles fueled by renewable hydrogen in future decades. As efforts to reduce CO₂ by 70 or 80% by 2050 receive high priority, aggressive short-term actions to reduce short-lived greenhouse pollutants hold promise. The US, Europe and Japan are phasing in high efficiency PM filters which will also reduce black carbon emissions dramatically.