Development of Emission Factors for a Urban Road Network Based on Speed Distributions

Average speeds are widely used in emission models to develop emission factors for emission estimations. However, using speed distributions instead of simply average speeds may improve the accuracy of the emission estimations because speed distribution represents speed profiles better in a real-life network. To investigate the feasibility of incorporating speed distributions instead of average speeds, the research for this paper collects massive emission and traffic activity data. First, the relationship between emission factors and average speeds was developed. Second, the speed distributions during daytime hours (6:00 to 21:00) for classified roads were analyzed and it was found that speed distribution on the expressway followed the bimodal distribution, while that on arterials and collectors followed the same distribution pattern, but with a single peak. Third, the research developed emission factors for the road network based on speed distributions, then compared them with those using traditional average-speed-based method. The comparative analysis showed that even though both emission factors by these two distinguished methods presented a similar variation trend, the results from the average-speed-based method were lower. Although the relative differences of the two methods were less than 10%, they tended to increase during peak hours. Finally, the research identified two reasons for those increased differences. First, speed distributions are more scattered during peak hours, and secondly the relationship between average speeds and emission factors is nonlinear in nature, so the relative differences in the low speed fraction increased more significantly during peak hours.

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• Supplemental Notes:
  • This paper was sponsored by TRB committee ADC20 Transportation and Air Quality.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Li, Ming
  • Yu, Lei
  • Zhai, Zhiqiang
  • He, Weinan
  • Song, Guohua
• Conference:
  • Transportation Research Board 94th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2015-1-11 to 2015-1-15
• Date: 2015

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 18p
• Monograph Title: TRB 94th Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Arterial highways; Estimating; Exhaust gases; Expressways; Peak periods; Speed distribution
• Uncontrolled Terms: Emission models
• Subject Areas: Environment; Highways; I15: Environment;

Filing Info

• Accession Number: 01556278
• Record Type: Publication
• Report/Paper Numbers: 15-2731
• Files: PRP, TRIS, TRB, ATRI
• Created Date: Mar 3 2015 11:43AM