Methods and results of field testing of a retrofitted freight train with composite brake blocks

Legal limits will be applied to pass-by noise of railway vehicles in Switzerland. As a consequence, existing freight wagons have to be retrofitted. The exchange of cast iron brake blocks by composite ones is a well-known low-cost measure to reduce pass-by noise. The Swiss Agency for the Environment (BUWAL) commissioned a measurement campaign in the year 2003 to define the noise limit, test conditions and maintenance procedures for retrofitted freight wagons.The test was set up in order to allow the control, or at least the knowledge of all relevant parameters concerning track, vehicles, test and boundary conditions. A track section was reconstructed. The test train was arranged with one reference group of wagons with cast iron brake blocks and several groups of wagons with composite brake blocks and different characteristics. As all wagon groups were operated together in one test train, boundary conditions and test parameters were identical for all wagons.The noise reduction achieved relative to cast iron block braked vehicles was in the expected range. Additionally, it could be observed that standard procedures in infrastructure and freight wagon maintenance do not ensure a sustained noise reduction. Several effects destroy this noise reduction. Measures to ensure a qualified noise reduction sustained for the full lifetime of a freight wagon were identified.