A case study on the noise effects of elevating existing train tracks



When modeling rail noise on an elevated track, there are several adjustments that need to be considered relative to modeling at-grade operations. These adjustments include the effects of re-radiated noise from the track and support structure, reduced ground attenuation due to an elevated noise source and a reduction in the potential for shielding from adjacent rows of buildings.  These adjustments are built into the model as a part of the design of a project.  This case study examines a unique situation where a project involved elevating existing at-grade tracks to eliminate a bottleneck related to an at-grade crossing of two perpendicular train tracks.  The project elevated one main track over the other and shifted the track closer to noise sensitive receivers. The US Federal Transit Administration and Federal Railroad Administration guidance, which were used to assess noise impacts, produced unexpected results during the initial assessment due mainly to the assumptions regarding the changes in shielding and ground attenuation with the elevated structure.  This presentation will discuss the initial assumptions used in the project, the limitations of the model relative to changes in shielding and ground attenuation, and the solutions that were implemented to obtain reasonable results for the impact assessment.