Research work on the new assessment of environmental indicators using equipment from the PEMS group (Portable Emission Measurement Systems) with motor vehicles is being developed. Due to the miniaturization of equipment, there are new measurement possibilities for more and more numerous groups of vehicles, including two-wheelers. The article presents the research and a summary of the results of a moped equipped with a two-stroke engine, approved in accordance with the Euro 3 standard. The research object is mainly used for driving in urban traffic. Therefore, the research route was created as the first communication frame in the Poznań agglomeration. In the analysis of the results, the author's M toxicity index was proposed, which is based on the assumption that CO2 emission is a measure of the correctness of the combustion process. The equipment from the PEMS-AxionR/S+ group, characterized by small dimensions and low weight, was used to determine the actual motion parameters and the emission of toxic compounds. In the analysis of the measurement results, dimensionless indicators of toxicity M of gaseous compounds were determined and a comparative analysis was made with the values of other objects obtained in the course of previous research (motorcycle, passenger car, off-road vehicle, hybrid bus and agricultural tractor). Due to the engine design (two-stroke type), the worst environmental indicators were obtained for CO and HC compared to other tested vehicles.