Emissions by rail transport account for around 1% of total pollutant emissions. The greatest negative influence on human health is made by PM, NOx, and others pollutants. Our article describes the methodology for measuring emissions (CO, NO_x, PM, and CH) into the air by rolling stock on which the experimental measurements of emissions are based. Comparison of emissions by the stock company Lietuvos geležinkeliai old (TEP70BS), re-motorized (2M62K), modernized (2M62M, ČME3ME, ČME3MG), and new (ER20CF) locomotives, railcars (620 M), and diesel trains (RA-2) into the atmosphere is carried out. As the study carried out in 2009 shows, the tested emissions into the air by diesel locomotive engines (pollutant kg/fuel ton) decreased significantly (up to 40%) when compared to the study carried out in 2003. Emissions of sulphur dioxide into the air from rolling stock in 2009 significantly decreased against 2003 as the allowable sulphur content in diesel fuel decreased from 0.2% to 0.001%.