Discrepancies between type-approval and real-world fuel consumption and CO2 values in 2001-2011 European passenger cars

Published: 2012.04.04

 Peter Mock,  John German, Anup Bandivadekar, Iddo Riemersma 

In order to limit the negative effects of climate change and to reduce dependency on oil imports, the European Union (EU) needs to reduce its GHG emissions by 80-95% below 1990 levels by 2050. A reduction of at least 60% by 2050 with respect to 1990 (70% with respect to 2008) is required from the transport sector, the only sector in which GHG emissions have increased since 2005 (+30% compared to -7% for all sectors). 

For passenger cars, accounting for two thirds of the GHG emissions from the EU’s transport sector, a voluntary self-commitment by the automotive industry to reduce the level of emissions for new vehicles was reached 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 COper kilometer (g/km) for 2008 was missed. In 2007 a decision was taken to introduce mandatory regulatory measures and 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. 

Given the success of the EU CO2 performance standards for passenger cars it is evident that the existing 2015 and 2020 targets have to be affirmed and additional post-2020 targets have to be set in order to put the EU road transport on a pathway to meet the long-term (2050) target, while allowing manufacturers sufficient lead-time to develop the required technologies for meeting the targets. However, the performance standards only affect the type approval value for individual vehicles. Therefore, it is of great importance to ensure that reductions in the level of CO2 emissions measured in the laboratory during the type approval test are also realized under real-world conditions. 

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. 

This paper compares fuel consumption / CO2 values of passenger cars from different sources and aims at quantifying the discrepancy between laboratory type-approval values and real-world values, including a retrospective analysis for the years 2001-2011 to determine if the gap between the two datasets has increased over time. Potential explanations for the discrepancies found are discussed and possible practical solutions for the future outlined. 

Based upon analyses 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 ICCT found that the gap between type-approval and “real-world” fuel consumption / COvalues increased from about 8% in 2001 to 21% today, with a particularly strong increase since 2007. Potential reasons for this development 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. In order to eliminate existing discrepancies as much as possible and to ensure that future improvements in vehicle technology result in real-world reductions of COand fuel consumption, a number of changes to the existing test cycle, test procedure and compliance testing are recommended.