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Because of its safety, reliability and efficiency, diesel is the predominant power source for public transit, school and intercity bus services nationwide. Among public transit agencies, diesel and diesel-hybrid buses account for about 75 percent of the national fleet.
According to the American Public Transportation Association (APTA), more and more Americans are taking public transportation. In fact, ridership is the highest it has been since 1956 and has been growing since 1995. In 2014, Americans took 10.8 billion trips on public transportation to get to work, to school and to neighboring cities.
America’s transit bus fleet is also one of the newest and cleanest heavy-duty fleets around. The new clean diesel bus technology of today is the result of an interconnected system of clean fuels, advanced engine design and exhaust or aftertreatment technologies working together to reduce emissions to near-zero levels. The latest federal standards virtually eliminate emissions from new diesel buses, reducing particulate matter (PM) and nitrogen oxides (NOx) by 98 percent from 1988 levels resulting in significant clean air benefits by reducing emissions of particulate matter and ozone forming compounds to near zero.
In 2013, 77 percent of transit buses were powered by diesel engines and fuel, or diesel hybrid engines. Of that, almost half were powered by a diesel engine that met or exceeded the first clean diesel standard for model year 2007 and another 27 percent of buses were powered by an engine that met or exceeded the stricter emission standard for model year 2010.
Many cities have begun using the latest in diesel-hybrid technology to allow their transportation systems to be not only more efficient but also more environmentally friendly. Also, a growing number of transit districts are incorporating the use of renewable biodiesel fuels into their diesel bus fleets, further improving their environmental and climate sensibilities.
New technologies are also being used to upgrade (or "retrofit") older diesel engines. Retrofitting devices are reducing key pollutants from existing bus fleets by up to 90 percent. Take a minute to learn more through Why Retrofit.
Clean diesel buses offer significant operational advantages over many alternative fuels, and assure reliable, durable and cost-efficient bus transportation.
A community will get more clean air for the dollar with a clean diesel bus fleet compared to CNG. Clean diesel buses are 20 to 25 percent less expensive than CNG buses, and do not depend on the separate fueling infrastructure required for CNG. Buying new diesel buses and retrofitting older buses allows transit agencies to convert a greater portion of fleets to clean diesel in order to meet state emissions requirements.
An analysis by the Clean Air Task Force illustrated the major emissions gains clean diesel buses have achieved. The analysis shows the air quality benefits of replacing older buses with newer clean diesel technology and a comparison of clean diesel and CNG buses.
| Vs. 2000 Diesel | NOx | Particulate Matter | Hydrocarbon |
|---|---|---|---|
| 2012 Clean Diesel | -94% | -98% | -89% |
| 2012 CNG | -80% | -99% | -100% |
Source: Clean Air Task Force – “Clean Diesel versus CNG Buses: Cost, Air Quality & Climate Impacts”
San Francisco Municipal Transportation Agency: Mayor Edwin M. Lee has announced a contract that includes a firm order for 61 diesel-electric hybrid 60-foot buses and options for up to an additional 363 diesel-electric hybrid 40-foot and 60-foot buses.
Chicago Transit Authority: CTA has begun introducing 300 new clean diesel 40-foot buses with an option to order an additional 150 diesel buses.
Detroit Department of Transportation: Mayor Mike Duggan unveiled the first of 80 new clean diesel buses in addition to two diesel-electric hybrid buses.
Southeastern Pennsylvania Transportation Authority: SEPTA has begun introducing 70 new 60-foot diesel-electric hybrid buses in the Philadelphia area with another 115 buses to be delivered in 2015.
New Jersey Transit:The board of NJ Transit has voted to spend up to $395 for the purchase of 772 clean diesel commuter coaches that are scheduled to begin delivery in 2016.
New York City Metropolitan Transportation Authority: New York City announced last summer that it would remove a quarter of its 1,677 hybrids from the city's roads and replace them with clean diesel models.
What is Clean Diesel?
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