The paper presents the reasons behind on-road vehicle exhaust emission testing. The latest legislation has been presented in the paper applicable in the EU as well as the research potential of the Institute of Combustion Engines and Transport of Poznan University of Technology. The presentation of the results of the on-road tests pertains to passenger vehicles, buses and non-road machinery (construction machinery, tractors) and aircraft. The comparison of the exhaust emissions from different means of transport under real traffic conditions constitutes an important trend included in the normative legislation related to exhaust emissions