Influence of driving cycles on unit emissions from passenger cars

Small samples of petrol engine or diesel cars, equipped with or without cat alysts, were tested over 36 driving cycles divided into four categories - s tandard cycles and three sets of cycles more representative of real-world d riving conditions. The tests addressed standard gaseous pollutants and fuel consumption and also less frequently measured pollutant such as CH4. In th e 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 ECE 15 cycle. Then unit emissions are compared over the four driving cycle fami lies. As compared to representative cycles, the standardised cycles underes timate hot emissions by almost 50% for petrol engine cars and 30% for diese l vehicles. Conversely, the results obtained for the three representative c ycle families are in relatively close agreement with each other - within ap proximately 10%. However? the cinematic properties of the three families di ffer. Finally, we demonstrate that weighting all emission data equally, not taking into account the weight of each cycle in overall traffic, introduce s significant biases, particularly when plotting emission vs. average speed curves. (C) 2000 Elsevier Science Ltd. All rights reserved.