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New York City Transit Hybrid and CNG Transit Buses: Interim Evaluation Results - page 15 / 64





15 / 64


West Farms

Gun Hill



126th Street

Mother Clara Hale

100th Street


M.J. Quill


  • Jackie Gleason

  • East New York

  • Flatbush

  • Fresh Pond

  • Ulmer Park


  • Jamaica

  • Queens Village

  • Casey Stengel

Staten Island

  • Castleton

  • Yukon

This evaluation focuses on the West Farms depot in the Bronx and Mother Clara Hale depot in Manhattan. Other depots, including Jackie Gleason, Queens Village, Fresh Pond, and Manhattanville, were also involved in the activities described in this report.

Emissions Reductions Drive the Need for CNG and Hybrid Propulsion

The U.S. transit market, including NYCT, has been under public pressure to reduce emissions in large transit buses—especially those in urban areas. Since the early 1990s, emissions regulations have focused significant reductions of particulate matter (PM) and oxides of nitrogen (NOx) on heavy diesel engines. As shown in Table 2, transit bus applications have been specifically targeted. In the late 1990s, CNG transit bus propulsion technology emerged as the cleanest available emissions option for transit agencies. However, significant start-up costs and capital investments required to successfully operate CNG buses have kept many transit agencies looking for other options. Hybrid technology has created significant interest as that possible alternative.

Diesel bus propulsion technology has also made emissions reduction improvements and is required to become much cleaner in the next few years. PM levels have been restricted to a low level of 0.05 g/bhp-hr since 1996. This level of PM has been addressed by changes in control of engine combustion, and, in some cases, a diesel oxidation catalyst (DOC) was added.

Political pressure at local levels continues to lower fleet PM levels. Extremely low levels of PM have been achieved using a passive regenerative diesel particulate filter (DPF) in conjunction with ultra low sulfur diesel (ULSD) fuel. ULSD is defined to be diesel fuel with a sulfur content less than 15 ppm. The sulfur content of the diesel fuel must be low to keep the DPF’s catalyst working properly. Many transit agencies are using DPFs and ULSD for new buses and as retrofits to older diesel engines to minimize fleet PM levels. By the end of 2006, nearly all diesel fuel for on-road applications is required to be ULSD. The PM level is planned to be restricted for


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