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Influence of driving cycles on unit emissions from passenger cars
Published May 31, 1999 by Technical University of Graz in Austria
Small samples of petrol engine or diesel cars, equipped with catalysts or not, were tested over 34 driving cycles divided into four categories - standard cycles and three sets of cycles more representative of real-world driving conditions. The tests addressed standard pollutants and also less frequently measured pollutants such as CH4 and N2O. In the first part of this paper we examine cold emissions in order to assess the duration of the cold start impact and the representativity of the cold ECE15 cycle. Then unit emissions are compared over the four driving cycle families. As compared to representative cycles, the standardised cycles underestimate hot emissions by almost 50% for petrol engine cars and 30% for diesel vehicles. Conversely, the results obtained for the three representative cycle families are in relatively close agreement with each other - within approximately 10%. However, the kinematic properties of the three families differ. Finally, we demonstrate that weighting all emission data equally, not taking into account the weight of each cycle in overall traffic, introduces significant biases, particularly when plotting emission vs. average speed curves.