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From laboratory to road: A 2015 update

This 2015 update to a series begun in 2013 analyzes eleven data sources covering fourteen years, six countries, and almost 600,000 vehicles. The analysis shows that in the EU the gap between official vehicle CO2 emissions and real-world CO2 emissions continues to grow—from 8 percent in 2001 to 38 percent in 2014.

Since 2001 average type-approval CO2 emission values of new European passenger cars have decreased by 27 percent. 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 and 2014, showed, there is a gap between the 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 identifes 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 2014). 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.


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Emissions modeling