A combined vehicle specific power and laboratory emissions approach to real driving CO2 emission estimation for light-duty vehicle

Abstract

The influence of CO₂ on Earth’s climate warming is significant. To quantitatively evaluate RDE (Real Driving Emission) CO₂ emissions based on laboratory test cycles, ten China 6 light-duty vehicles were tested under the WLTC (Worldwide Light-duty Driving Test Cycle), CLTC-P (China Light-duty Vehicle Test Cycle), and RDE tests. This study identified that the reference CO₂ emission factors for conventional vehicles and PHEVs (Plug-in Hybrid Electric Vehicles) were 9.59–27.36 % and 32.30–45.01 % higher than the tested CO₂ emissions, respectively. This suggested that setting CO₂ emission limits based on the method in fuel consumption regulation could not effectively reduce CO₂ emissions, particularly for PHEVs. The linear relationship between laboratory and RDE average CO₂ emission in each VSP (Vehicle Specific Power) Bin suggested that the RDE average CO₂ emission can be corrected to reduce the impact of driving behaviour and traffic conditions. The laboratory-based RDE emissions were obtained by replacing the frequency ratios of each VSP bin in the RDE tests with those from the laboratory cycles, and this method was helpful to establish RDE CO₂ emission limits. For PHEVs, when the WLTC was used as a benchmark, RDE CO₂ emissions from aggressive driving and traffic congestion were 9.48–14.87 g/km and 20.04–20.31 g/km, respectively. These emissions were 5.49 g/km and 20.52 g/km when the CLTC-P was used as the benchmark.