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Particulate emission from diesel engines is one of the most important pollutants in urban areas. As a result, particulate emission control from urban bus diesel engines using particle filter technology is being evaluated at several locations in the US. A project entitled “Clean Diesel Demonstration Program” has been initiated by NY City Transit under the supervision of NY State DEC and with active participation from several industrial partners. Under this program, several NY City transit buses with DDC Series 50 engines have been equipped with continuously regenerating diesel particulate filter system and are operating with ultra low sulfur diesel (< 30 ppm S) in transit service in Manhattan since February 2000. These buses are being evaluated over a 8-9 month period for operations, maintainability and durability of the particulate filter.

With growing concerns about NOx and particulate matter (PM) emissions from diesel engines, stricter regulations are being implemented which require advanced emission control technology. This paper discusses the combination of a diesel particle filter system (DPF) with a low pressure exhaust gas re-circulation (EGR) system to provide four way emission control of NOx, PM, CO and HC from existing heavy duty diesel engines. The combined EGR-DPF system has been used in Europe over the past 4 years, with over 1200 systems installed on urban buses and other on-road applications. This system has shown 40-60% NOx reduction in addition to >90% CO, HC and PM reductions. Recently, several field trial programs have been initiated to evaluate the performance and durability of this EGR-DPF system under US operational conditions. These include retrofit applications on urban buses and on construction trucks.