Abstract: A method of classifying an object, in particular of classifying a vehicle by evaluating the degree of correlation between an image data set corresponding to an image of at least part of the vehicle and each of a plurality of reference data sets each of which corresponds to a reference image of a vehicle comprises the steps of establishing the vehicle's aspect and selecting the plurality of reference data sets from a larger group of such data sets on the basis of the vehicle's aspect. By selecting from the larger group only those reference data sets which correspond to the vehicle's aspect, faster classification is achieved for a given level of processing resources. Alternatively, for a given processing or classification rate, the level of processing resources may be reduced compared to the prior art.