The impact of speed post-processing methods on regional mobile emissions estimation

Song Bai, Yu Nie, Debbie A. Niemeier*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Average roadway segment travel speeds play an important role in estimating stabilized running vehicle emissions. Currently stabilized, or hot, running emissions are computed based on speeds produced during the travel demand modeling process. Speed data from the travel forecasting models are widely recognized as being insufficiently accurate for air quality purposes. Frequently post-processing techniques are seen as the most cost-effective means of improving the accuracy of the speed estimates. Using the Sacramento Metropolitan area, this paper focuses on the impacts of different speed post-processors on regional peak period emissions inventories. The results indicated that most post-processed speeds produce consistently and significantly higher running emissions, particularly in locations with heavy traffic. The observed differences in emissions between different types of post-processed speeds vary with congestion level, pollutant type and the underlying approach encapsulated in the speed post-processor calculations. The Sacramento case study suggests that the post-processor used to develop speeds for the purposes of calculating on-road emissions inventories can significantly influence the emissions inventories.

Original languageEnglish (US)
Pages (from-to)307-324
Number of pages18
JournalTransportation Research Part D: Transport and Environment
Issue number5
StatePublished - Jul 2007


  • Air quality
  • Emission inventory
  • Mobile emission
  • Speed post-processing

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Transportation
  • Environmental Science(all)

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