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Automobile time-resolved emissions of CO, CO2, HC, and NOx during engine and catalyst warm-up have been analyzed by fitting the emissions to the product of vehicle tractive power and a series of gaussian functions whose relative magnitudes were allowed to vary in time. From this analysis the emissions were discerned into four components : (1.) the emissions due to vehicle power demand, (2.) key-on emissions, (3.) a catalyst warm-up emissions function, and (4.) a fast idle emissions function. Both the emissions associated with the engine and the catalyst warm-up decline exponentially with time. Two additional characteristics (a.) emissions occurring during idling and (b.) emissions due to catalyst cooling during idle were observed, but not quantified.