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On July 29 the U.S. Environmental Protection Agency (EPA) and U.S. Department of Transportation (DOT) issued a Supplemental Notice of Intent (SNOI) on 2017–2025 Model Year Light-Duty Vehicle greenhouse gas (GHG) Emissions and corporate average fuel economy (CAFE) Standards. See here for a summary of the key elements, including a comparison of the targets with other global vehicle GHG regulations.
While this summary does take into account differences in test cycles and normalizes to the European driving cycle (NEDC), it does not take into account differences in the vehicle fleet structure. With the help of a few calculation steps it is possible to carry out a thought experiment to estimate what would happen if the U.S. 2025 standard for passenger vehicles were applied to the European Union (EU) vehicle fleet.
The U.S. GHG regulation is based on the footprint of a vehicle, i.e., the wheel-track multiplied with the wheel-base. This approach ensures that larger vehicles are allowed to emit more GHG emissions than smaller vehicles. The advantages of such a size-based approach compared to a vehicle weight-based approach, as it is currently used in the EU, have been discussed in detail in this ICCT white paper. The average footprint of new passenger cars in the EU-27 (all 27 EU member states) in 2010 was 3.95 square meters (source: EU CO2 monitoring data / EEA). This equals 42.5 square feet. For a vehicle of this size the U.S. 2025 passenger car target would be 135 grams of CO2 per mile (g/mi) (source: Federal Register Vol. 76, No. 153).
The average engine power of a new passenger car in the EU-27 in 2010 was 84 kilowatt (kW) (source: ICCT internal data). The average curb weight was 1,283 kilogram (kg) (source: EU CO2 monitoring data / EEA, vehicle mass in running order adjusted to curb weight). This results in a power-to-weight ratio of 0.0655 kW/kg. In the U.S. the average engine power of new passenger cars in 2010 was 192 horsepower or 143 kW (source: U.S. EPA). The average curb weight was 3,199 pounds or 1,451 kg (source: U.S. EPA, loaded weight adjusted to curb weight). The power-to-weight ratio for the U.S. therefore equals 0.0986 kW/kg. This is an indication that passenger cars in the U.S. are not only 13% heavier than in the EU but also are equipped with approximately 50% more engine power per kg of weight, when comparing the fleet averages for both markets. The difference in weight is reasonably taken into account when adjusting for vehicle size, due to a similar relationship between vehicle weight and vehicle footprint in Europe and the U.S. This leaves us with adjusting for vehicle power. This is not a simple task, due to the interdependencies of different variables. The NEMS model offers a way of roughly estimating the effects (source: U.S. DOE); the difference in power-to-weight ratios would accordingly translate into a 13% difference in fuel economy in miles per gallon (mpg). In our case, the 135 g/mi target equals 66 mpg. Accounting for the power-to-weight difference, the resulting fuel economy would be 75 mpg or 117 g/mi.
All the previous calculations were carried out based on the U.S. vehicle test cycle, the CAFE cycle. For taking into account differences in the dynamics of the test cycles a set of conversion factors was developed. Applying the respective conversion factor a CO2 target of 117 g/mi in the CAFE cycle would translate into 121 g/mi or 75 grams per kilometer (g/km) in the European NEDC cycle.
In the U.S., EPA intends to propose A/C credits for passenger cars of up to 18.8 g/mi, if manufacturers apply systems with a low global-warming potential (GWP). In the EU these systems are mandatory and no credits can be earned in the context of the vehicle GHG regulation. 18.8 g/mi translate to approximately 12 g/km in the NEDC test cycle. Therefore, if manufacturers were to make full use of the A/C credits offered, the 2025 fleet target would be 87 g/km. Please note that there are other credits in both, the U.S. and EU target systems, that have not been taken into account here.
The market share of new diesel passenger cars is less than 1% of all new passenger cars in the U.S. (source: U.S. EPA). For EU-27 the diesel share was 51% in 2010 (source: EU CO2 monitoring data / EEA). Assuming that diesel vehicles typically have 10% lower CO2 emissions than gasoline vehicles with the same performance characteristics, the calculated values have to be corrected by 5% when applying the U.S. target to the EU fleet in order to take into account the difference in the diesel vehicle market share. This leads to a CO2 target of 71 g/km (max. 83 g/km including A/C credits).
At this point in time the above calculations cannot be more than a rough estimate and need to be substantiated by further analysis. Yet it is interesting to see the result when applying the planned U.S. 2025 targets for passenger vehicles to the European vehicle market. This would mean that the EU vehicle fleet on average would have to comply with a CO2 target of approximately 70 g/km. Taking into account A/C credits in the U.S. system, the corresponding value would be 83 g/km at maximum. Compared to the 2010 average of 140 g/km this would require a reduction of 40% to 50%. The current target of the European Commission for 2020 is set at 95 g/km. The calculations above illustrate that the U.S. target for 2025 is more aggressive than this EU 2020 target when taking into account the differences in the vehicle fleets. As the extensive analyses by U.S. EPA and NTHSA demonstrate, the required CO2 emission reductions are technically and economically feasible in the US, and upcoming research activities by ICCT will assess the respective potential for the EU in more detail.