Objectives

The general objective of Quiet-Track is to provide step changing track based noise mitigation systems and maintenance schemes, to provide reliable improved TSI based rolling noise calculation procedures with harmonized monitoring of the required input parameters and to provide track noise management tools, for use in noise mapping and hot spot action plans according to the END, for use as engineering tools and solutions in new railway projects and in refurbishment projects and for use by the track maintenance managers and track maintenance industry.

The existing rolling noise models will be enhanced with new fundamental features: the integration of the low frequency noise emission and of the actual wheel rail contact conditions for more accurate predictions of the noise emitted by the track. This is very important in an urban environment where low frequency noise penetrates much easier trough nearby windows than the higher frequency noise. Taking into account the actual wheel rail contact conditions is also very important (e.g. multiple point contact in curves) in order to enhance the accuracy of the rolling noise prediction models. The precision of the actual rolling noise models for tangent track, obtained by experienced users, is +/- 3 dB(A) on the global noise level and +/- 6 dB(A) on the individual octave bands in the averaged equivalent noise spectrum. The rolling noise in the low frequencies bands (below 250 Hz) cannot be calculated accurately with the existing models, based on statistical energy analysis. The aim is to obtain the same precision as above in curves and to obtain a global noise level precision of +/- 3 dB(A) when only considering the low frequency bands (up to 250 Hz). The existing models use rail and wheel roughness values which are determined at a couple of selected locations or which come from general databases. On-board monitoring systems will be developed to make it be possible to use the real roughness values and track decay rate values measured directly at the track location where maintenance action is required or where mitigating solutions have to be applied.

New track solutions will be developed within Quiet-Track which yield a noise reduction performance of at least 6 dB(A) in comparison with the global rolling noise measured on a well maintained standard track in the network of the participating infra managers. A well-maintained track is defined as a track which is ground (standard rail defect removal grinding) at least once a year for urban networks and which is, for the conventional rail tracks, additionally tamped at least once a year for geometrical defect correction. The solutions have to be applicable to tram, LRT and metro tracks as well as to conventional tracks in the whole European Union.

This why emphasis is also placed on low noise embedded tracks, very often used in a city environment with mixed traffic. The embedded tracks have in average a 3 dB(A) lower noise emission than corresponding non embedded tracks. Quiet-Track aims at adding an additional 3 dB(A) noise reduction to the embedded track systems by appropriate selection of the embedment material characteristics. The solutions to be developed in Quiet-Track should not back-up a poor initial design. This is why attention is paid to a good initial design with a procedure (project deliverable) for selecting the best rail type and the best rail hardness in terms of minimising the noise related wear. This is especially important in urban networks but also very valuable for conventional rail networks.

A procedure for checking the economic viability of the solutions will be developed.  This procedure will use recognized noise cost factors (from HEATCO study) to calculate the monetary benefit for comparison with the additional solution related investment cost and/or maintenance cost. This will result in holistic noise management plans for the introduction of the noise abatement solutions and for the noise related track maintenance.

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