Research and/or engineering questions/objective: The issue of air pollutant emissions from rail transport or from its infrastructure is a field that has been neglected and therefore existing databases are very little and heterogeneous. The objective of this research is to identify possible data gaps and contribute to close them through an extensive literature research, various series of measurements in the ambient air close to railway tracks as well as on a test bench for brakes, dispersion simulation and a hazard analysis and risk assessment. Methodology: Air quality measurements were carried out in a free railway track, a marshaling yard and a passenger train station in order to cover the different areas of rail transport and its infrastructure. At each measurement site, four sets of instruments were installed at different distances from the railway tracks, both leeward and windward. From this, it was expected to obtain a decline curve that indicates that the highest concentrations of pollutants are found near the tracks and as the distance becomes greater, the influence of trains decreases. The mass-related particulate matter mass concentrations, particle number concentrations, PM composition and size distribution as well as NO2 concentrations were measured. At one station, various meteorological parameters such as temperature, relative humidity, direction and wind speed were measured. At the station located closest to the train tracks, a camera was installed to generate a record of the activities on the tracks. Results of the monitoring in the ambient air: The evaluations of the measurements carried out in the ambient air show that although on small time scales (minutes) the passage of trains e.g. can cause very high concentrations of air pollutants, but with regard to longer averaging periods (days, weeks, months) the additional loads caused by the railways are low. The mass-related PM10 additional pollution near the track averaged 2 µg/m³ and the nitrogen dioxide (NO2) additional pollution was less than 1 µg/m³ (open section) or 3 µg/m³ (marshalling yard). Furthermore, the elements S, Mn, Mg, Ba, Cu, Zn, Mo, Cr and Al could be detected. The rail-related additional loads decreased rapidly with increasing distance from the tracks. The average PM10 additional loads at the free railway track had already fallen to around 10% of the additional loads close to the track, even with good windward-leeward conditions at a distance of 55 m. Limitations of this study: The study was carried out at each type of site (free railway track, marshalling yard, train station, underground train station) for several weeks or even months, but only once per type. Desirably a repetition at different sites per type would have delivered a range of values and a better understanding of the representativeness of the measurements performed. What does the paper offer that is new in the field in comparison to other works of the author? Not much focus was set on the air pollution caused by rail traffic in general. This gap of knowledge and data will be reduced, but for sure not be closed entirely. Conclusion: With the help of the findings determined in this project, not only with the one from the air pollution monitoring, but also from the test bench measurements, specific emission factors are to be derived and existing air pollutant emission and dispersion models are to be validated. In addition, a pollutant quantification and a toxicological risk assessment of the emissions and ambient air pollution from rail traffic are carried out. These results will be available in a further stage of the project and will be presented in the future to the scientific community.

Dr.-Ing. Ulrich Vogt, Head of Department of Flue Gas Cleaning and Air Quality Control, University of Stuttgart; Mr. Daniel Ricardo Obando Nunez, PhD student, University of Stuttgart/Germany, Institute of Combustion and Power Plant Technology; Mr. Dieter Straub, co-worker, University of Stuttgart/Germany, Institute of Combustion and Power Plant Technology; Dr. Ingo Duering, head of office, Lohmeyer Ltd, engineering office; Dipl.-Ing. Wolfram Schmidt, co-worker, Lohmeyer Ltd, engineering office; Dr. Annette Bitsch, Head of department, Fraunhofer Institute for Toxicology and Experimental Medicine; Dipl.-Ing. Eckert Fritz, head of division, Institute of Railway Technology; Dr. Sabrina Michael, head of division, German Centre for Rail Traffic Research