View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by International Institute for Applied Systems Analysis (IIASA) Manuscript – Final and authoritative paper published in Environmental Science & Technology, 18 Oct 2019. https://pubs.acs.org/doi/abs/10.1021/acs.est.9b04123 1 When is enough? Minimum sample sizes for on-road 2 measurements of car emissions 3 Yuche Chen‡ *, Yunteng Zhang‡, Jens Borken-Kleefeld† * 4 ‡Department of Civil and Environmental Engineering, University of South Carolina, USA 5 †International Institute for Applied System Analysis, Laxenburg, Austria 6 * Corresponding author: Yuche Chen,
[email protected]; Jens Borken-Kleefeld, 7
[email protected] 8 9 Key words: Monte Carlo simulation, bootstrap, in-use surveillance, diesel car, Europe, Euro 6, 10 mean, variance, remote emission sensing. 11 Manuscript – Final and authoritative paper published in Environmental Science & Technology, 18 Oct 2019. https://pubs.acs.org/doi/abs/10.1021/acs.est.9b04123 12 ABSTRACT 13 The power of remote vehicle emission sensing stems from the big sample size obtained and its 14 related statistical representativeness for the measured emission rates. But how many records are 15 needed for a representative measurement and when does the information gain per record become 16 insignificant? We use Monte Carlo simulations to determine the relationship between the sample 17 size and the accuracy of the sample mean and variance. We take the example of NO emissions 18 from diesel cars measured by remote emission monitors between 2011 and 2018 at various 19 locations in Europe. We find that no more than 200 remote sensing records are sufficient to 20 approximate the mean emission rate for Euro 4, 5 and 6a,b diesel cars with 80% certainty within 21 a ±1 g NO per kg fuel tolerance margin (~±50 mg NO per km).