MBTA Bus Fleet Emissions Screening Using Remote Sensing Technology

Exhaust emissions from transit buses has been a hot topic for years. In order to improve local air quality, many agencies have invested millions of dollars in advanced and clean fuel technologies to reduce emissions from their bus fleets. Generally, the only information available about the emission characteristics of these vehicles comes from expensive engine-and chassisdynomometer tests. Relatively little is known about actual on-road performance, especially as vehicles age. While virtually all states have emissions inspection and maintenance (I/M) programs for light-duty vehicles, only sixteen have I/M programs for heavy-duty vehicles that evaluate exhaust emissions on a regular basis. The purpose of any emissions I/M program is to identify “high emitters” that require maintenance to reduce their emissions back to normal and expected levels. Virtually all of these heavy-duty I/M programs use opacity meters to evaluate exhaust smoke levels as a proxy for particulate emissions. Massachusetts is one of the states with a heavy-duty I/M program, but it has not proven very effective at evaluating actual in-use emissions performance of the buses operated by the Massachusetts Bay Transportation Authority (MBTA) in Boston. In 2003, the MBTA developed a comprehensive plan to reduce bus fleet emissions, which includes use of ultra low sulfur diesel fuel fleet-wide, engine upgrades and retrofit of diesel particulate filters on older buses, as well as purchase of new emission-controlled diesel (ECD) and compressed natural gas buses. As part of their overall commitment to ensure that their revitalized fleet will continue to have low emissions throughout its life, the MBTA also decided to implement an enhanced I/M program specifically focused on measurement of in-use emissions to identify and correct high emitters. M.J. Bradley and Associates has worked with the MBTA and a citizen’s advisory committee to identify and test various technologies that could be used as fleet emissions screening tools for it’s enhanced I/M program. The two most promising technologies evaluated are Portable Emissions Monitoring Systems (PEMS) and Remote Sensing Devices (RSD). This paper will discuss the technology evaluation process, including descriptions of each technology, the results of in-use emissions evaluations of the MBTA fleet using both PEMS and RSD, and current plans for the MBTA’s new enhanced I/M program.


  • English

Media Info

  • Media Type: Print
  • Features: Figures;
  • Pagination: 11p
  • Monograph Title: 2005 Bus & Paratransit Conference

Subject/Index Terms

Filing Info

  • Accession Number: 01001934
  • Record Type: Publication
  • ISBN: 1931594163
  • Files: TRIS
  • Created Date: Jul 11 2005 1:54PM