Official vs. real-world road-load parameters in EU vehicle efficiency testing
Driving resistances of light-duty vehicles in Europe: Present situation, trends, and scenarios for 2025
The driving resistances—mass, aerodynamic drag, and rolling resistance—of a vehicle directly affect fuel consumption and CO2 emissions. Reducing driving resistances can significantly aid manufacturers in achieving CO2 emission targets.
Available studies on driving resistances and their impacts mainly focus on the mass parameter. Rolling resistance is strongly controlled by tire suppliers and aerodynamic drag by vehicle manufacturers, and data normally are not published. This study comprehensively investigates all vehicle-based parameters influencing light-duty vehicle (LDV) driving resistances. Existing databases on European LDV mass, aerodynamic drag, and tires were evaluated to quantify the current status and trends of Europe’s LDV fleet and segment averages. Technical scenarios for 2025 were derived, and achievable reductions in terms of CO2 emissions were assessed. Furthermore, trends for the U.S. market were derived from official road load databases published by the US EPA.
Potential load reduction scenarios for 2025 were created based on historical trends, best-in-class analyses, and assessments of future technology potential. The paper estimates the total CO2 reduction potential in 2025 at between 14% (Scenario 1) and 25% (Scenario 2). Both scenarios assume that engines will be downsized and tailored to the specific performance requirements of each vehicle version. All three types of driving resistance parameters can contribute by rather similar amounts, although mass reduction gives the highest potential benefit of the three resistance parameters. The CO2 sensitivity of rolling resistance is comparatively low, but low rolling resistance tires clearly exceeding the current market averages are already available. These are ready and easy to introduce, but need to be promoted by regulatory measures. Aerodynamic drag improvements are also promising, especially if the ongoing trend of enlarged frontal areas can be stopped, and the improvements in further streamlining the vehicle body can be fully transformed into CO2 savings.