Rushton, CE, Tate, JE orcid.org/0000-0003-1646-6852, Shepherd, SP orcid.org/0000-0002-4420-3382 et al. (1 more author) (2018) Interinstrument comparison of remote-sensing devices and a new method for calculating on-road nitrogen oxides emissions and validation of vehicle-specific power. Journal of the Air & Waste Management Association, 68 (2). pp. 111-122. ISSN 1096-2247
Abstract
Emissions of nitrogen oxides (NOx) by vehicles in real driving environments are only partially understood. This has been brought to the attention of the world with recent revelations of the cheating of the type of approval tests exposed in the dieselgate scandal. Remote-sensing devices offer investigators an opportunity to directly measure in situ real driving emissions of tens of thousands of vehicles. Remote-sensing NO₂ measurements are not as widely available as would be desirable. The aim of this study is to improve the ability of investigators to estimate the NO₂ emissions and to improve the confidence of the total NOx results calculated from standard remote-sensing device (RSD) measurements. The accuracy of the RSD speed and acceleration module was also validated using state-of-the-art onboard global positioning system (GPS) tracking. Two RSDs used in roadside vehicle emissions surveys were tested side by side under off-carriageway conditions away from transient pollution sources to ascertain the consistency of their measurements. The speed correlation was consistent across the range of measurements at 95% confidence and the acceleration correlation was consistent at 95% confidence intervals for all but the most extreme acceleration cases. VSP was consistent at 95% confidence across all measurements except for those at VSP ≥ 15 kW t−¹, which show a small underestimate. The controlled distribution gas nitric oxide measurements follow a normal distribution with 2σ equal to 18.9% of the mean, compared to 15% observed during factory calibration indicative of additional error introduced into the system. Systematic errors of +84 ppm were observed but within the tolerance of the control gas. Interinstrument correlation was performed, with the relationship between the FEAT and the RSD4600 being linear with a gradient of 0.93 and an R² of 0.85, indicating good correlation. A new method to calculate NOx emissions using fractional NO₂ combined with NO measurements made by the RSD4600 was constructed, validated, and shown to be more accurate than previous methods. Implications: Synchronized remote-sensing measurements of NO were taken using two different remote-sensing devices in an off-road study. It was found that the measurements taken by both instruments were well correlated. Fractional NO₂ measurements from a prior study, measurable on only one device, were used to create new NOₓ emission factors for the device that could not be measured by the second device. These estimates were validated against direct measurement of total NOₓ emission factors and shown to be an improvement on previous methodologies. Validation of vehicle-specific power was performed with good correlation observed.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018, Christopher E. Rushton, James E. Tate, Simon P. Shepherd, and David C. Carslaw. Published with license by Taylor & Francis. This is an open access article under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > Institute for Transport Studies (Leeds) > ITS: Spatial Modelling and Dynamics (Leeds) |
Funding Information: | Funder Grant number DEFRA Dept for Env. Food & Rural Affairs Not Known DEFRA Dept for Env. Food & Rural Affairs Not Known European Commission Joint Research Cntre Inst Prospective Technological Studies No External Ref Calderdale Council N/A DEFRA Dept for Env. Food & Rural Affairs No External Ref DEFRA Dept for Env. Food & Rural Affairs No External Ref DEFRA Dept for Env. Food & Rural Affairs Not Known DEFRA Dept for Env. Food & Rural Affairs N/A Aberdeen City Council Marischal Aberdeen City Council Marischal College No Ext Ref |
Depositing User: | Symplectic Publications |
Date Deposited: | 10 Nov 2017 15:13 |
Last Modified: | 20 Mar 2018 14:24 |
Status: | Published |
Publisher: | Taylor & Francis |
Identification Number: | 10.1080/10962247.2017.1296504 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:123688 |