EU SAM group recommends real driving CO₂ monitoring

7 December 2016

The High Level Group of the European Commission’s Scientific Advice Mechanism (SAM) has recently published an opinion on the measurement of CO₂ emissions from cars, recommending a monitoring requirement for real driving CO₂ emissions (RDE).

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Under the current NEDC laboratory test procedure, there has been a significant and growing gap between the CO₂ emissions of light-duty vehicles certified at type approval and their average real-world emissions. The WLTP procedure, based on a more realistic laboratory test cycle, will be introduced in the EU in September 2017. The new procedure is expected to substantially reduce, but not eliminate this gap, noted the SAM report.

The SAM High Level Group report has been prepared to inform the European Commission proposal for post-2020 emission standards for light-duty vehicles, which is expected to be published in 2017. The report concluded that:

• In order to ensure the representativeness of the type approval test, a framework for the monitoring of real driving CO₂ emissions is required. This should consist of an exploitation of CO₂ data obtained from real driving emissions testing for pollutants using Portable Emissions Measurement Systems (PEMS), the development of a targeted ex-post Real Driving Emissions (RDE) methodology for CO₂, and the introduction of a formal reporting of fuel consumption from on-board vehicle diagnostic systems.
• A number of framework conditions must be met, including in particular the strengthening of regulatory oversight and technical capacity in Europe, and increased transparency of the whole process.
• Legislation on CO₂ emissions from road transport should be designed in a way that stimulates innovation and is able to adapt to the increasing take-up of new technologies such as plug-in hybrid and electric vehicles.
• The assumption that CO₂ emissions measured with the WLTP will be closer to real-world emissions is reasonable. However, while the WLTP has the potential to become a common reference globally, its further development is recommended with a formal review every five years to ensure that the gap between laboratory and real-world emissions is not growing.

The report also identified a number of areas where more scientific and analytical wok is needed. These areas include the development of the ex-post RDE methodology for CO₂ emissions, development of a standardized OBD system for fuel consumption monitoring, and development of methods to capture the full life cycle of carbon emissions related to new types of vehicles powered by energy sources other than diesel and petrol.

A recent study by the ICCT has shown that the average gap between passenger vehicle type-approval test results and in-use fuel consumption/CO₂ increased to 42% in 2015. According to the ICCT, about three quarters of this gap is explained by vehicle manufacturers exploiting flexibilities in the current type approval procedure (e.g., specially prepared tires or fully charging the vehicle’s battery before testing). The remainder of the gap is explained by the deployment of technologies that have a greater effect on fuel consumption during laboratory testing than under real-world driving conditions (e.g., stop-start technology) and by ensuring that options that tend to increase fuel consumption—such as running the vehicle’s air conditioning—are turned off during laboratory testing.

Source: European Commission