How to Reduce Particulate Matter Concentrations in a Railway Metro System?

Environmental surveys performed in different case studies round the world have often observed high concentrations of particulate matter (both PM10 and PM2.5) in railway metro systems. These particulate matter concentrations are generated by mechanical friction between rail and wheels and between wheels and brakes interactions aside from the re-suspension of these particles caused by the train passage. In this paper was investigated the importance in considering useful system devices to reduce particulate matter concentrations in a metro system. A measurement survey was performed in 2017 in the metro Line 1 of Naples - Italy. From the results it is possible to conclude that PM concentrations measured in metro system equipped with system devices able to reduce PM levels are significantly lower than the ones measured in "traditional" metro systems. This result allow to poses the bases for both the design and the retrofitting of metro systems round the world.