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On-Road Remote Sensing of Automobile Emissions in the Tulsa Area: Fall 2013

The authors conducted a five-day remote sensing study in the Tulsa, Oklahoma area in late September and early October of 2013. The remote sensor used in this study measures the ratios of CO, HC, NO, SO₂ and NH₃ to CO₂ in motor vehicle exhaust. From these ratios, the authors calculated the percent concentrations of CO, CO₂, HC, NO, SO₂ and NH₃ in the exhaust that would be observed by a tailpipe probe, corrected for water and any excess oxygen not involved in combustion. Mass emissions per mass or volume of fuel could also be determined. The system used in this study was configured to determine the speed and acceleration of the vehicle, and was accompanied by a video system to record the license plate of the vehicle and, from this record, the vehicle’s model year. Since fuel sulfur has been nearly eliminated in US fuels SO₂ emissions have followed suit and while the authors collected vehicle SO₂ measurements, the authors did not calibrate those readings and they are not included in the discussion of the results. The mean CO, HC, NO, NH₃ and NO₂ emissions for the fleet measured in this study were 13.4 g/kg (0.11%), 2.1 g/kg (57ppm), 1.5 g/kg (109ppm), 0.43 g/kg (54ppm) and 0.14 g/kg (6ppm), respectively. When compared with previous measurements from 2005 the authors found that mean CO (-60%) and NO (-46%) emissions have experienced significant reductions while HC (-4.5%) and NH₃ (-14%) emissions have declined less. Emission deterioration between similar model years during the intervening eight years was remarkably low, especially for CO where there was statistically no difference between 10 to 30 year old vehicles. The emissions measurements in this study exhibited a gamma distribution and the skewedness has increased since the last measurements in 2005. The highest emitting 1% of the measurements was responsible for 31%, 42%, 25%, 15% and 50% of the CO, HC, NO, NH₃ and NO₂ emissions, respectively. The recent recession has had a measurable effect on the age of this Tulsa vehicle fleet. The dramatic economic downturn that began in late 2008 and continued through 2010 reduced both new vehicle sales and the retirement (scrappage) of older vehicles. Consequently, the average age of the Tulsa fleet increased from 6.7 (last measured in 2005) to 7.8 years. The largest loss in sales occurred in model year 2009 (37% lower than 2007) and 2010 (23% less than 2007). As a result of the aging of the fleet, tailpipe emissions have not decreased over this time period as fast as they might have done in the absence of the economic downturn. If the 2013 data are adjusted using the fleet age distribution seen in 2005 it is found that CO, HC, NO and NH₃ emissions would have been 17% lower for CO (2.3 g/kg), 9% lower for HC (0.2 g/kg), 26% lower for NO (0.4 g/kg) and 6% lower for NH3 (0.03 g/kg) emissions. These differences are statistically significant for all of these species but the HC emissions. The on-road emissions that would otherwise have been replaced by the purchase of newer vehicles were found in the 10 to 20 year old vehicles.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 39p

Subject/Index Terms

Filing Info

  • Accession Number: 01539888
  • Record Type: Publication
  • Report/Paper Numbers: CRC Report No. E-106
  • Files: TRIS
  • Created Date: Oct 6 2014 2:34PM