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Nitrous oxide (N2O) is an important trace gas in the atmosphere not only because of its large global warming potential (GWP) but also because of the role in the ozone depletion in the stratosphere. It has been known that soil is the largest natural source of N2O in global emission. However, anthropogenic sources contributing from industrial section is likely to increase with rising the energy consumption, and transportation as well. In this study, a total of 32 gasoline-powered passenger vehicles (ranging from small to large engine's displacement and also ranging from aged catalyst to new catalyst) were tested on the chassis dynamometer system in order to elucidate the characteristics of N2O emission from automobiles under different driving modes. Ten different driving modes developed by NIER were adapted for the test. The results show that the N2O emission decreases logarithmically with increase of vehicle speed over the all test vehicles (N2O emission = -0.062 Ln (vehicle speed) + 0.289, r2=0.97). It revealed that the larger engine's displacement, the more N2O emission were recorded. The correlation between N2O emission and catalyst aging was examined. It found that the vehicles with aged catalyst (odometer record more than 8,0000km) emit more N2O than those with new catalyst. Average N2O emission was 0.086±0.095 N2O-g/km (number of samples=210) for the all test vehicles over the test driving modes.