Research Projects

Project at a Glance

Project Status: complete

Report Published March 1996:

Title: On-board heavy-duty truck mobile emission testing in support of mobile source emission inventories and on-board emissions factor for diesel bus.

Principal Investigator / Author(s): Acurex Environmental Corporation

Contractor: Acurex Environmental Corporation

Contract Number: 92-924

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


The objective of this project was the development and testing of on-board emissions measurement capability for heavy-duty vehicles utilizing a new unique measuring technique under Contract # 92-924, On-Board Heavy-Duty Truck Mobile Emission Testing in Support of Mobile Source Emission Inventories for the California Air Resources Board (CARB). Follow-up testing was funded by the United States Environmental Protection Agency (U.S. EPA) under Contract #68-D2-0063, On-Board Emissions Factors for a Diesel Bus. The work was conducted between August 1993 and February 1995.

The technology approach is presented in Section 2. It is based on extensive experience Acurex Environmental gained while testing utility power plants and other emission sources requiring on-line emissions testing. Section 3 discusses how the stationary source testing technology was adapted to measure emissions from a diesel bus outfitted with special sensors and the equipment that was proposed and used during the tests. It should be understood that this project was a concept demonstration and was not intended to result in a measurement apparatus that would be routinely utilized to measure emissions from diesel trucks, buses or tractors. Commercial equipment satisfying that criteria would have to be substantially reduced in size, requiring significant commercial product development effort. Section 4 presents the various test plans and Section 5 describes tests that were carried out. Section 5 discusses, in particular, many of the difficulties that were encountered during the tests resulting in the need to repeat the first chassis dynamometer test at the Los Angeles County Metropolitan Transportation Authority (LACMTA). Section 6 presents test data evaluations and results. Section 7 presents recommendations for further development of the system and further evaluation of the collected test data. Appendix A contains the technical paper presented at the CRC On-Road Vehicle Emissions Workshop at the Hyatt Islanwa, San Diego, California in April 1995 and Appendix B and C contain test data collected during the chassis dynamometer and on-road testing, respectively

During the data analysis, we were able to successfully correlate the emission measurements from the Acurex Environmental system with those from the LACMTA system, despite some instrument errors that occurred with the Acurex Environmental system. There were problems both with the air flow measurement and with the calibration and response time of the NOx analyzer. This made it difficult to directly compare the data from these two systems. However, we were able to develop adjustment factors for the flow rate and the NOx measurement which overcame these errors to produce results that agreed very well with the results from the LACMTA system. Further work needs to be done to improve the flow measurement technique and to optimize the emissions analyzers. These fmdings are discussed in detail in Sections 5 and 6.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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