Measurement of car engines exhaust pollutants emissions is very important because of their harmful effects on the environment. This article presents the assessment of repeatability of the passenger car engine exhaust pollutants emission research results obtained in the conditions of a chassis dynamometer. The research was conducted in a climate chamber, enabling the temperature conditions to be determined from − 20 to + 30 °C. The emission of CO, CH₄, CO₂, NO_X, THC, and NMHC was subjected to the analysis. The aim of the research is to draw attention to the accuracy of the pollutant emission research results in driving cycles, and the comparison of pollutant emission results and their repeatability obtained in successive NEDC cycles under cold and hot start conditions. The results of the analysis show that, in the case of a small number of measurements, the results repeatability analysis is necessary for a proper interpretation of the pollutant emission results on the basis of the mean value. According to the authors’ judgment, it is beneficial to determine the coefficient of variation for a more complete assessment of exhaust emission result repeatability obtained from a small number of measurements. This parameter is rarely presented by the authors of papers on exhaust components emission research.

The problem of global warming and the related climate change requires solutions to reduce greenhouse gas emissions, in particular CO₂. As a result, newly manufactured cars consume less fuel and emit lower amounts of CO₂. In terms of exhaust emissions and fuel consumption, old cars are significantly inferior to the more recent models. In Poland, for instance, the average age of passenger cars is approximately 13 years. Therefore, apart from developing new solutions in the cars produced today, it is important to focus on measures that enable the reduction in CO₂ emissions in older vehicles. These methods include the adaptation of used cars to run on gaseous fuels. Natural gas is a hydrocarbon fuel that is particularly preferred in terms of CO₂ emissions. The article presents the results of research of carbon oxides emission (CO, CO₂) in the exhaust gas of a passenger car fueled by petrol and natural gas. The emissions were measured under the conditions of the New European Driving Cycle (NEDC) test and in real road tests. The test results confirm that compared to petrol, a CNG vehicle allows for a significant reduction in CO₂ and CO emissions in a car that is several years old, especially in urban traffic conditions.

Among the solutions that make it possible to reduce CO₂ emissions in the transport sector, particularly in urban traffic conditions, are hybrid vehicles. The share of driving performed in electric mode for hybrid vehicles is highly dependent on motion resistance. There are different methods for determining the motion resistance function during chassis dynamometer testing, leading to different test results. Therefore, the main objective of this study was to determine the effect of the chassis dynamometer load function on the energy demand and CO₂ emissions of a full-hybrid passenger car. Emissions tests according to the New European Driving Cycle (NEDC) were carried out on a chassis dynamometer for three different methods of determining the car’s resistance to motion. The study showed that adopting the motion resistance function according to different methods, results in differences in CO₂ emissions up to about 35% for the entire cycle. Therefore, the authors suggest that in the case of tests carried out with chassis dynamometers, it is necessary to also provide information on the chassis dynamometer loading function adopted for the tests.

Until now, passenger cars before getting permission to sell were tested in the laboratory conditions in order to determine the amount of harmful gas compounds emission and average fuel consumption. However, studies have shown that, during real driving, emission results significantly differ from those obtained in the laboratory. For this purpose, in the European Union was created a new procedure for conducting of driving cycle WLTP (World Harmonized Light-Duty Procedure) taking into account road test (Real-Driving Emissions, RDE). The article presents selected results of pollutant emissions research using the HORIBA OBS 2200 road analysis system. The results show that emission in real traffic conditions can lead to exceeding vehicle emission standards. The largest exceeded emission limits occurred for the urban and motorway parts, while the smallest ones for the rural part. In relation to EURO 5, the limits for THC (exceeding by 9%) and CO (exceeding by 49%) were not included in the emission limit.