Dealing with the Gap between Type-Approval and In-Use Light Duty Vehicles Fuel Consumption and CO₂ Emissions: Present Situation and Future Perspective

Abstract

There is increasing evidence suggesting that real-world fuel consumption and CO2 improvements in the last decade have been much less than those measured during type-approval tests. Scientific studies have found that the offset between officially reported values and real-world vehicle CO2 emissions in Europe has constantly increased over the last years. The difference between officially reported and actual CO2 emissions of vehicles has three main implications: (i) it undermines the effectiveness of CO2 regulations in reducing greenhouse gas emissions in Europe; (ii) it distorts competition between vehicle manufacturers; (iii) it undermines innovation. As a fundamental step to deal with this issue, the European Commission has already replaced the old and outdated test procedure used so far in the emission type-approval of vehicles with the worldwide harmonized light vehicles test procedure (WLTP). Being a lab-based test procedure, the WLTP, by its nature, can only cover part of the CO2 gap. There is therefore increasing pressure to integrate the current type-approval system with additional measures based on real-world measurements. One of the options under discussion is to use the CO2 emissions measured during the real driving emission test. The objective of the present paper is to assess the validity of this proposal and to propose other possible ways to deal with the CO2/fuel consumption gap. In particular, the paper presents experimental evidence on the variability of the CO2/fuel consumption of a vehicle, questioning the idea that a single central estimate of these quantities may be sufficient.

Segment-Based CO₂ Emission Evaluations From Passenger Cars Based on Deep Learning Techniques

“…In order to close the gap between the CO₂ emissions results estimated by two major techniques (top-down approaches focusing on fuel market interactions and bottom-up approaches focusing on technological details), researchers have developed multiple simulation programs, such as greenhouse gas emission models and vehicle energy calculation tools, for the compilation of emission inventories [40][41][42][43][44][45]. From this point of view, the simulation is useful to compensate the limitations of the laboratory test methods.…”

Measurements of the Emissions of a “Golden” Vehicle at Seven Laboratories with Portable Emission Measurement Systems (PEMS)

“…The emissions under real-life operation, though, are typically assessed by tunnel measurements [1], chasing tests (i.e., following cars with a mobile laboratory), on-road measurements with portable systems, or even laboratory measurements simulating real-world routes [2]. The differences between typeapproval and on-road values of vehicles was a big topic a few years ago in the European Union (EU), not only for pollutants emissions [3,4], but also for fuel consumption and CO 2 [5]. The situation significantly improved with the assessment of the vehicles on the road [6].…”

Benchmarking the driver acceleration impact on vehicle energy consumption and CO2 emissions

“…Nevertheless, the effectiveness of implemented measures depends on the reliability of the vehicle fleet carbon emission values. During the past decades, fuel consumption and CO 2 emissions of light-duty vehicles (LDVs) have consistently showed an apparent disparity between real-world and official certification values ( Weiss et al, 2011 ) ( Fontaras et al, 2017 ) ( Pavlovic et al, 2018 ). Despite the implementation in 2017 of the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) ( Tutuianu et al, 2013 , Ciuffo et al, 2015 , Commission Regulation (EU) 2017/1151, 2017 ) the evidence so far suggests that the emissions gap has not completely disappeared ( Pavlovic et al, 2018 ) (ICCT 2021) ( Dornoff et al, 2020 ).…”