Selecting a 2010 Bus Engine/Propulsion Technology

This paper describes how transportation agencies planning bus fleet procurements for year 2010 and beyond will have three primary choices for bus engine/propulsion technologies: compressed natural gas (CNG), emission controlled diesel (ECD), and diesel-electric hybrid (DEH). Each of these technologies is undergoing “generational” technology changes driven by increasingly more stringent Environmental Protection Agency (EPA) regulations in 2007 and 2010. Over the next 24 to 36 months, the incorporation of new, additional emission-reduction technologies will impact vehicle reliability and operating costs. However, factors other than cost, such as operational constraints and an agency’s ability to absorb new or evolving technology, will influence the selection of the preferred bus propulsion technology. It is anticipated that there will be some convergence of the capital costs of these three competing technologies over the next few years. The cost premium for CNG over diesel will substantially narrow, while the premium for DEH over diesel will also be reduced as hybrid bus volumes increase, energy storage improves, and the larger automotive market commercializes hybrid technology. Both ECD and CNG technologies will undergo a significant generational advancement by 2010, resulting in improved emissions; however, both will be accompanied by increases in capital and ongoing maintenance costs. The operational cost differential between these two technologies will primarily be driven by differential fuel price and infrastructure costs. DEH bus technology has matured significantly in recent years, and a substantial number of buses are now in regular service throughout North America. In addition, multiple studies show that DEH fleets are providing significant in-service fuel economy benefits, while achieving similar (if not better) reliability and similar (if not marginally lower) maintenance costs. However, these buses still have a significant capital cost premium, and it remains to be seen whether fuel and other savings can offset the higher cost of the vehicle and the increased long-term maintenance costs of the batteries and electric propulsion equipment. For 2010, other propulsion types such as hydrogen fuel cell and hydrogen ICE will be in various demonstration programs but will remain too expensive for large-scale fleet implementations. To make the best purchase decisions, agencies must consider the following factors, which this paper focuses in analyzing the differences between ECD, CNG, and DEH: (1) emissions; (2) reliability; (3) capital, operating and maintenance costs; (4) infrastructure investments; and (5) technology risks. These factors will define the “2010 Technology Ratings” used to compare each of the three choices. The Technology Ratings are based on a scale of 0 to 4 and range from Unacceptable to Excellent. Using these factors, a decision model can be built for an agency by applying an agency-specific “Importance Weighting” to each factor. The Importance Weightings are also based on a scale of 0 to 4 and range from very low to very high.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Tables;
  • Pagination: 5p
  • Monograph Title: Bus and Paratransit Conference and International Bus Roadeo, 2007

Subject/Index Terms

Filing Info

  • Accession Number: 01051665
  • Record Type: Publication
  • ISBN: 1931594252
  • Files: TRIS
  • Created Date: Jun 16 2007 10:05AM