ICCT study finds increasing discrepancy between type-approval and real-world fuel consumption in European cars
30 April 2012
A new study by the International Council on Clean Transport (ICCT) has found that the gap between type-approval and “real-world” fuel consumption / CO2 values for European cars increased from about 8% in 2001 to 21% today, with a particularly strong increase since 2007. The study was based on the analysis of more than 28,000 user entries of the German fuel consumption database spritmonitor.de and more than 1,200 vehicle models tested by Europe’s largest automobile club ADAC.
The authors—Peter Mock, John German, Anup Bandivadekar and Iddo Riemersma—suggest that potential reasons for this increasing divergence include: (i) increasing use of existing tolerances and loopholes in the determination of road load, vehicle weight, laboratory test temperatures, and transmission shifting schedules for type-approval; (ii) inability of the current test cycle, the NEDC, to represent real-world driving conditions; and (iii) increasing market share of vehicles equipped with air conditioning systems.
From a consumer perspective, most drivers are aware that there exists a gap between the fuel consumption they experience during everyday driving and the corresponding values that are listed in information brochures they obtain from their local car dealer, the internet, or other media sources. As this gap increases, a part of the CO2 and fuel consumption reductions achieved on paper do not pay back to consumers in fuel cost savings. This could lead to a situation where official type approval values provided by the vehicle manufacturers would lose credibility among consumers and where the willingness to invest into new vehicle technologies to reduce fuel consumption and CO2 emissions is reduced.—Mock et al.
To reduce its greenhouse has (GHG) emissions by 80-95% below 1990 levels by 2050, the EU requires a reduction of at least 60% by 2050 with respect to 1990 (70% with respect to 2008) from the transport sector—the only sector in which GHG emissions have increased since 2005 (+30% compared to -7% for all sectors).
The automotive industry agreed to a voluntary self-commitment for passenger cars to reduce the level of emissions for new vehicles in 1998/99. However, the annual rate of reduction between 1998 and 2006, as measured by the New European Driving Cycle (NEDC), was only between 0.6% and 2.2% and the target of 140 grams of CO2 per kilometer (g/km) for 2008 was missed. In early 2009 the first mandatory CO2 performance standards for passenger cars in the EU were adopted, setting a target of 130 g/km for 2015 and 95 g/km for 2020. In the course of setting mandatory standards, the annual rate of reduction of the average level of CO2 emissions from new passenger cars has increased from a rate of 1.7% in 2007 to 5.1% in 2011. The European average CO2 emission level in 2011 was 140.3 g/km compared to 158.7 g/km in 2007.
The ICCT paper focuses on new passenger cars in Germany—the largest market in Europe (3 million new passenger cars each year) and a major exporter to other countries (5.5 million passenger cars exported in 2010). Only CO2 values are reported; the conversion factors used are 2.43 kilogram (kg) CO2 per liter of gasoline and 2.65 kg per liter of diesel fuel.
In addition to identifying the growing discrepancy between type-approval and real world fuel consumption, the ICCT analysis confirms that there was a decrease in the level of CO2 emissions of new passenger cars in Germany since 2001. However, the magnitude of reduction in reality appears to be only about half of what is suggested by the type-approval values (about 7% instead of 15% since 2001).
These developments lead to two key concerns: a) From a policy maker perspective, to ensure that regulatory CO2 emission reductions result in similar ambient air emission reductions in order to achieve future greenhouse gas emission targets, b) From a consumers’ perspective, to avoid disappointment due to higher than expected fuel consumption, which could have negative implications for the willingness of consumers to invest into fuel efficient (and low-CO2 emission) cars in the future.—Mock et al.
The authors explain the existence of a gap between type-approval and real-world levels as due to:
Characteristics of the NEDC test cycle are not representative for real-life driving behavior (low accelerations, low maximum speed, high idling time, constant speeds instead of transients, favorable shifting points, etc.)
Cold start testing is performed at ambient temperatures close to 30 °C, while real life temperatures are lower, leading to higher fuel consumption.
The allowed tolerances and flexibilities in the road load test procedure cause the road load of type-approval vehicles to be lower than that of production vehicles.
At the type approval test the battery is charged to 100% capacity.
The type approval test weight is lower than the real-life average.
Vehicles are type-approved without the air conditioning system turned on (or any other power consuming equipment).
Other flexibilities and tolerances in the type approval test procedure are exploited to positively influence the test results (e.g. tolerance allowed to follow the NEDC speed trace, allowed 4% tolerance between measured and declared CO2 value, etc.)
The authors also make a number of recommendations to address the problem:
Monitor real-world emission reductions on a regular basis—preferably by independent research—in order to reveal and address gaps between type-approval and real-world emission levels in a timely and effective way.
Ensure that the coming World Harmonized Light-duty vehicle Test Procedure (WLTP)—expected to apply to the EU type-approval from after 2015—is as representative for EU real-world driving as possible.
Improve test procedures as well as test cycles.
Peter Mock, John German, Anup Bandivadekar, Iddo Riemersma (2012) Discrepancies between type-approval and real-world fuel consumption and CO2 values in 2001-2011 European passenger cars. ICCT Working Paper 2012-02
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