The Régie is working to "reduce as much as possible particulate emissions" Three trains of the RER A are already equipped and seven others should be before the end of the year. An air filtration system was tested in 2019 with Suez, but it needs to be reworked, because currently "too bulky and noisy" The authority that organizes transport in the region, under the aegis of Valérie Pécresse, is financing 57.3 million euros for the equipment.