Life cycle analysis of railway noise and vibration mitigation methodologies with respect to curve squeal noises

Wheel/rail interface inevitably induces a travelling source of sound and vibration, which spread over a long distance of rail network and neighborhood corridor. The sound and vibration can be generated in various forms and spectra. The undesirable sound and vibration, is often called ‘noise’, includes rolling noise, impact noise, curve noise, mechanical noise, airborne noise, wheel/rail noise, structure- and ground-borne noises. The noise and vibration that is transferred back through the vehicle body mainly affects ride quality, customer experience, and structural integrity of the rolling stocks, whereas the vibration that is transmitted from the rails to the supporting structure of the track plays a main role in rapid track degradation and potentially affects the surrounding structures. This paper focuses on the effectiveness of noise mitigation measures on curved tracks located in urban environments. It highlights the practical methods for mitigating curve squeals and flanging noises, which are often observed along freight corridors and track infrastructures with nonlinear geometries. It is important to note that rail freight curve noises, especially for curve squeals, can be observed almost everywhere and every type of track structures. The most pressing noise appears at sharply curved tracks where excessive lateral wheel/rail dynamics resonate with falling friction states, generating a tonal noise problem, so-call ‘squeal’. Therefore, this paper is devoted to systems thinking approach and life cycle assessment in resolving railway curve noise problems. The life cycle of fifty years has been selected as it is coincide with the majority of common design life for railway tracks catering freights, heavy haul trains, mixed traffics and heavy suburban trains globally. Based on assumptions commonly derived in rail industry, the life cycle analyses under variant extreme weather conditions reveal that the jetting method (or on-board wheel-based friction modifier) seems to be the most efficient method for mitigating curve noises, whilst the noise barrier seems to be the worst counterpart in a long curve section but this case is untrue for a sharp short curved track.