Analyzing on-road Emissions of Light-duty Vehicles with Portable Emission Measurement Systems (PEMS)
Emissions testing in the laboratory forms an essential part of the European type approval procedure for light-duty vehicles. The approach yields reproducible and comparable results and provides clear design criteria for vehicles that have to comply with applicable emission limits. Although emission limits have become increasingly stringent in the past decade, road transport remains the most important source of urban air pollution with respect to nitrogen oxides (NOX) and carbon monoxide in Europe. Several studies have indicated that in particular on-road nitrogen oxide emissions of light-duty diesel vehicles might substantially exceed emission levels as identified in the laboratory. Here, we address this problem by using Portable Emission Measurement Systems (PEMS) to analyze the on-road emissions of 12 light-duty diesel and gasoline vehicles on four test routes, representing rural, urban, uphill/downhill, and motorway driving. The results indicate that average NOX emissions of diesel vehicles (0.93 ± 0.39 g/km), including Euro 5 diesel vehicles (0.62 ± 0.19 g/km), substantially exceed the respective emission limits. The observed deviations range from a factor of 4-7 for NOX emission averages over entire test routes up to a factor of 14 for NOX emissions of individual averaging windows. By comparison, on-road NOX emissions of gasoline vehicles as well as CO (carbon monoxide) and THC (total hydrocarbon) emissions of both diesel and gasoline vehicles generally stay within Euro 3-5 emission limits. The tested light-duty diesel and gasoline vehicles emit during on-road testing on average 189 ± 51 g CO2/km (grams carbon dioxide per kilometre) and 162 ± 29 g CO2/km, respectively, thereby exceeding the CO2 emissions as specified during laboratory testing by on average 21 ± 9%. The cold-start emissions of both diesel and gasoline vehicles span over a large value range; NOX emissions exceed Euro 3-5 emission limits by a factor 2-14, CO emissions often exceed emission limits, and THC emissions are both below and above Euro 3-5 emission limits, respectively. The PEMS equipment is reliable and provides accurate emission measurements. PEMS are able to verify the proper operation of emission control technologies under a wide variety of normal operating conditions as well as test emissions from novel fuel/engine/after-treatment/powertrain technologies (e.g., parallel/serial (plug-in) hybrid vehicles. The PEMS procedure for light-duty vehicles is, however, relatively new and requires further refinement before being applied at large scale. The findings of this report indicate that the current laboratory emissions testing fails to capture the wide range of potential on-road emissions. A promising remedy for this problem may be attained by supplementing the laboratory test with complementary emission test procedures such as PEMS on-road testing. This report provides a first step into that direction, thereby contributing to a more comprehensive EU policy that assures compliance of light-duty vehicles with emission limits under normal conditions of use.
WEISS Martin;
BONNEL Pierre;
HUMMEL Rudolf;
MANFREDI Urbano;
COLOMBO Rinaldo;
LANAPPE Gaston;
LE LIJOUR Philippe;
SCULATI Mirco;
2011-01-24
Publications Office of the European Union
JRC62639
978-92-79-19072-8,
1018-5593,
EUR 24697 EN,
OP LB-NA-24697-EN-C,
https://publications.jrc.ec.europa.eu/repository/handle/JRC62639,
10.2788/23820,
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