The paper presents a method of preparation of statistical data in such a manner as to enable application of the COPERT IV method to calculate emissions resulting from the operation of light and heavy commercial vehicles, buses as well as motorcycles and mopeds. The paper also presents the results of calculations of emissions from these vehicles in Poland in 2014, made by means of the COPERT IV method with application of the proposed methodology. The results have been compared with data from emission inventories, and conclusions have been drawn concerning the reasonableness and possibility of applying the proposed methodology.