From laboratory to road: A 2016 update
Uwe Tietge, Sonsoles Díaz, Peter Mock, John German, Anup Bandivadekar (ICCT), and Norbert Ligterink (TNO)
Extends an analysis of the gap between official and real-world fuel consumption and CO2 emission values for passenger cars in Europe and investigates the reasons for the increasing gap.
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This 2016 update to a series begun in 2013 analyzes 13 data sources covering 15 years, six countries, and approximately 1 million cars. The analysis shows that, in the EU, the gap between official and real-world CO2 emission values continues to grow—from 9% in 2001 to 42% in 2015.
Since 2001 average official CO2 emission values of new European passenger cars have decreased by 29%. The rate of decline quadrupled after the EU introduced CO2 emission standards in 2009.
But the official vehicle CO2 emission values are determined by laboratory tests. As previous "From Laboratory to Road" reports, published in 2013, 2014, and 2015, showed, there is a gap between real-world and official CO2 values that has been increasing over time.
For an average consumer the gap now translates into additional fuel expenses on the order of €450 per year. Since vehicle taxation schemes and incentive schemes for low-carbon cars are based on official CO2 values, the gap may also lead to significant losses of tax revenue and a misallocation of public funds.
This update discusses a number of reasons for the increasing gap. Flexibilities in the type-approval procedure allow for unrealistically low driving resistances and unrepresentative conditions during laboratory testing (these flexibilities account for the majority of the gap in 2015). Fuel-saving technologies such as stop/start systems and hybrid powertrains also prove more effective at reducing CO2 emissions during laboratory testing than during real-world driving. Lastly, the type-approval process fails to take into consideration auxiliary devices such as air conditioning and entertainment systems. These devices consume energy during real-world driving and thus contribute to the gap.
The key implication of the study is the urgent need for improved test procedures. While a new type-approval procedure, the Worldwide harmonized Light vehicle Test Procedure (WLTP), will be introduced in the EU in 2017, the WLTP will not close the gap on its own. On-road tests, similar to the Real Driving Emissions (RDE) test procedure for air pollutants, and in-use conformity tests of randomly selected production vehicles should also be introduced.