Technology is available to reduce diesel vehicle and engine emissions in a cost-effective way. The ability to use diesel emission reductions for state implementation plan (SIP) and conformity purposes gives states and localities additional incentive to implement diesel retrofit projects. Diesel retrofit technologies reduce pollution from the existing diesel engine fleet by up to 90% for particulate matter (PM), up to 75% for nitrogen oxides (NOx), and up to 90% for volatile organic compounds (VOCs). Many diesel retrofit projects are being successfully implemented around the country. Clean diesel projects already initiated are expected to result in approximately 20,000 tons of particulate matter reduced over the life of the projects, with estimated public health benefits of about $5 billion.