European Commission, Joint Research Centre (JRC), Ispra 21027, Italy.
European Commission, Joint Research Centre (JRC), Ispra 21027, Italy.
Sci Total Environ. 2022 Aug 1;832:154943. doi: 10.1016/j.scitotenv.2022.154943. Epub 2022 Apr 5.
Monitoring the fuel consumption gap between official and real-world measurements is of great interest to policy makers and researchers. This study explores how sampling methods (simple random, stratified and quota sampling) can be used to supplement and validate the monitoring. Three user datasets were utilised to simulate the fuel consumption gap of the 11.6-15.5 million vehicles registered annually in the European Union (2018-2020). Results suggest that a simple random sample of 16,240 vehicles is sufficient to estimate accurately the fleets' average fuel consumption gap. Stratified sampling can reduce the sample size to less than 4,500 vehicles. To estimate accurately the fuel consumption gap of each manufacturer, the sample size increases to approximately 17,200 vehicles. The increase in sales of plug-in hybrid vehicles in 2020 led to an increase of the average fuel consumption gap by 8% and its standard deviation (variability) by 20%. This higher variability resulted in a more than double sample size, compared to previous years. It was also found that the introduction of the Worldwide Harmonized Light vehicles Test Procedure (WLTP) reduced the average gap by 20-24%. This study highlights the viability of a sampling scheme to estimate the fuel consumption gap by monitoring less than 0.05% of the fleet. Moreover the study draws attention to the need for further analysis and understanding of the real-world use and fuel consumption of plug-in hybrid vehicles.
监测官方和实际测量之间的燃料消耗差距对于政策制定者和研究人员非常感兴趣。本研究探讨了抽样方法（简单随机、分层和配额抽样）如何用于补充和验证监测。利用三个用户数据集模拟了欧盟每年注册的 1160 万至 1550 万辆汽车的燃料消耗差距（2018-2020 年）。结果表明，简单随机抽取 16240 辆车就足以准确估计车队的平均燃料消耗差距。分层抽样可将样本量减少到不到 4500 辆。要准确估计每个制造商的燃料消耗差距，样本量增加到大约 17200 辆。2020 年插电式混合动力汽车销量的增加导致平均燃料消耗差距增加了 8%，其标准差（可变性）增加了 20%。与前几年相比，这更高的可变性导致样本量增加了一倍多。研究还发现，全球轻型车辆测试程序（WLTP）的引入将平均差距缩小了 20-24%。本研究强调了通过监测不到 0.05%的车队来估计燃料消耗差距的抽样方案的可行性。此外，该研究还提请注意需要进一步分析和了解插电式混合动力汽车的实际使用和燃料消耗情况。
