The article presents a comparison of exhaust emission results obtained in on-road tests using the latest legislative proposals relating to passenger cars. The results were analyzed with reference to the classical method (considering all measurement data) and the measurement window averaging method, also referred to in the literature as the EMROAD method. In this approach, measurement windows are defined (based on carbon dioxide emission data from the WLTC test), and the corresponding on-road emissions are determined for the RDE test. The study included Euro 6c vehicles equipped with gasoline engines and diesel engines. The gasoline engines featured direct fuel injection, while the diesel vehicle was equipped with a particulate filter and a selective catalytic reduction system to reduce nitrogen oxide emissions. In on-road tests, the correction factors depended on the applied technical solutions. For direct-injection gasoline engines in the Euro 6 class, the values remained below 1. A characteristic feature was that the correction factors were higher in the urban part of the test and lower for the entire RDE cycle. A different pattern was observed for diesel vehicles: in on-road tests, the correction factors were higher for the entire test than for the urban part of the RDE test. The conducted research and the determined emission indices made it possible to evaluate the environmental performance of vehicles from different emission classes and, at the same time, to provide a basis for proactive measures aimed at reducing selected pollutants from passenger cars.