Noise

Railway Induced Vibration

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The UIC Sustainable Unit working group on vibration has just published the Vibrations State-of-the-Art Report. In modern daily life, people are exposed to many types of vibration. The vibration is often accepted as obvious and no cause for concern, for example when driving a car or when taking a lift. In some cases, vibration originating from sources outside the house may be felt inside (...)

The UIC Sustainable Unit working group on vibration has just published the Vibrations State-of-the-Art Report.

In modern daily life, people are exposed to many types of vibration. The vibration is often accepted as obvious and no cause for concern, for example when driving a car or when taking a lift. In some cases, vibration originating from sources outside the house may be felt inside dwellings. This applies for example to heavy road traffic, trams and railway lines, both on surface lines and in tunnels. This vibration is typically observed as a gentle trembling of the house, usually of the floor people are standing on. The vibration itself can generate a rumbling sound, caused by the vibrating building radiating sound into the rooms (known as structure-borne sound). Secondary noise, i.e. rattling of loose doors, pottery, etc., can further amplify the audible noise or make it more noticeable.

Whether or not the vibration can be perceived depends on many factors, including distance to the source, speed and type of the traffic, quality of the road or track, type and build-up of the ground, and the construction of the building itself. Modifications performed in the soil (modification of the sewer network, for example) or even in adjacent buildings can give rise to an increase of vibration or ground-borne noise. Contrary to popular belief, vibration caused by passing trains is far too weak to cause even cosmetic damage (when the structural integrity of the building is affected) to buildings. Nevertheless, residents affected by vibration may experience annoyance and could thus voice concern. The degree to which the vibration sensation is masked by audible noise can also play a role, as well as personal sensitivity.

Railway-induced vibration was first noticed and labelled an issue in relation to underground train lines. It is only in recent times that the vibration from surface lines is getting more attention. Vibration is usually accompanied by ground-borne noise. The relative significance of these two phenomena depends mainly on the soil type. In countries with stiff soils, e.g. solid rock, ground-borne noise is generally more important than vibration, and dominant vibration frequencies are higher (i.e. around 50 Hz). In countries with soft soil such as clay or peat, vibration may be more important than ground-borne noise and dominant vibration frequencies are lower (around 5 Hz). This difference in soil type is an important factor affecting the performance and selection of mitigation measures.

For railways, vibration is most often generated by the contact between the train wheel and the railway track. The vibration then travels from the track, through the ground and into the building foundation. Generally, the strength of ground vibration reduces as one moves away from the track. However, the strength of vibration may increase when moving up floors inside the building due to resonances of the building structure.

There are a number of mitigation measures available that can be applied to either the track or the vehicle. Because local factors (terrain, construction of individual buildings, space etc.) have a strong influence, the effectiveness of these measures can differ greatly from case to case. The prediction of vibration levels is thus a complex process and often involves a large degree of uncertainty. In some cases, especially existing situations, the cost of mitigation may be prohibitively expensive. In assessing vibration and designing mitigation, expert judgement is required.

Guidelines for acceptable levels of vibration vary from country to country. The impact on residents depends strongly on individual and local circumstances. Therefore, any values mentioned in this report should be interpreted with great care.
For new situations (railway lines or residential and other property development), it may be required to assess vibration and propose mitigation measures in the environmental impact assessment. For existing situations, most countries do not have a legal obligation for railway companies to assess and mitigate vibration. However, railways take residents’ concerns seriously and, where appropriate, will support an assessment and consider mitigation measures.

The present report reflects the state of the art, which is mainly based on the experience of the European rail-operating community, publications from academia and consultancy, the results of the collaborative research projects RIVAS and Cargovibes, and the work of standardisation committees, insofar as it has been published.

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Railway Noise in Europe - State of the art Report - 2016

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Railway transport is the most sustainable transport mode, as it consumes less energy, needs less space and produces less CO2 than any other transport mode. However, noise has long been the main environmental challenge for railway stakeholders. The public and their political representatives urge railway stakeholders to become quieter. But a lot has been achieved, and more activities are on the (...)

Railway transport is the most sustainable transport mode, as it consumes less energy, needs less space and produces less CO2 than any other transport mode. However, noise has long been the main environmental challenge for railway stakeholders. The public and their political representatives urge railway stakeholders to become quieter. But a lot has been achieved, and more activities are on the way. This report describes the recent developments and their impact.

This report is an update of a previous version, entitled Railway Noise in Europe, which was published in 2010. During the past few years’ significant developments have taken place with respect to legislation and approach, approval and application of technical solutions, responsibilities of the various parties involved and ways to persuade stakeholders to engage in common enterprises to improve the noise situation. At the same time, there is greater insight into the effects of noise on exposed residents and a growing pressure on railway enterprises and infrastructure managers to reduce noise where feasible. As a consequence, a significant noise reduction has been achieved for millions of European residents. Passenger vehicles with noisy cast iron brake blocks have been phased out in large parts of Europe. The retrofitting of significant parts of the rail freight fleet with composite brake blocks has started. In addition, old noisy wagons are scrapped every year and the new wagons replacing them are much quieter. Many kilometers of noise barriers have been constructed, a large number noise insulated windows installed and measures on the track introduced.

There are a wide variety of stakeholders concerned with the management of railway noise. The rail sector has to deal with regulations and demands from the European Commission, national authorities, regional and city authorities, citizen groups and individuals, and to align these requirements with the railways’ own strategies. This report describes how this is currently done and seeks to inform the associated discussions.

Noise exposure and the cost of noise control must be effectively managed if rail is supposed to increase its market share, and in doing so to reduce the total environmental impact of the whole transport sector.

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Railway Noise - Technical Measures Catalogue
July 2013

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There is a growing awareness of the impact of railway noise on public health, which has resulted in pressure from line-side inhabitants, governments and health organizations for increased noise mitigation. As a consequence, noise can be a limiting factor for many railway operations, introducing additional costs for mitigation, demands for limits on availability/capacity and resistance to expansion of the network.

Recent years have seen the development of new, and refinement of existing, strategies and technologies for noise management. Railway companies often face calls to implement these, and demonstrate that progress has been made with the use of new and innovative technology.

By collating best practice and case studies from "real life" tests and adding the theoretical knowledge in this Catalogue, UIC stimulates the implementation of publically available knowledge, demonstrate the progress that has been made and also manage stakeholder expectations.

This Noise Technical Measures Catalogue surveys recent developments for three topics in
separate chapters:

  • Curve Squeal
  • Noise from freight marshalling yards
  • Noise from switches

In addition, one final chapter is dedicated to measures against rolling noise: rail and wheel dampers, K and LL blocks, noise barriers and acoustic grinding.
Curve squeal Curve squeal is a highly annoying sound that is radiated by trains running through sharp curves. Much progress has been made during the past decades in understanding this phenomenon. Mitigation measures aim at avoiding squeal events or at least reducing their duration or strength. Flange lubrication and top-of-rail application of friction modifiers have demonstrated to be very effective (reduction1: 5-20 dB(A)), provided that the dosing devices receive constant and dedicated maintenance. Friction products can be applied from trackbased as well as vehicle-mounted devices and there are many manufacturers and suppliers of such devices.

Special bogie designs, aiming at improved steering performance in curved as well as straight track, also reduce squeal noise and are potential solutions for the future, provided that safety issues can be solved adequately.

Noise from freight marshalling yards
Marshalling yards are areas where freight trains are decoupled and coupled. Because of the large scale of the yard, mitigation by noise barriers is no option. Among the most important noise sources are screeching rail brakes (retarders), peak noise from coupling vehicles and starting diesel engines, and steady noise from locomotive engines and auxiliary systems. Recently, new solutions for noisy rail brakes have been developed, showing promising noise performances (5-15 dB(A)). For stationary noise of several locomotives, technical modifications have been developed. Stationary noise of diesel engines, for example to operate cooling vents, may be avoided by using a way-side electric power supply.

Noise from switches
Switches and crossings are among the most sensitive parts of the railway system, claiming a large part of the maintenance budget. Switches and crossings also produce noise: impact noises from joints (if present) and screeching noise similar to curve squeal. In a traditional switch, a wheel encounters several gaps, causing a train to produce a rattling sound. Jointless switches are state-of-the-art nowadays (2-4 dB(A)) on lines where trains run at operational speeds. Squeal noise and flange rubbing noise in switches may receive the same treatment as squeal noise in curves (5-20 dB(A)).

Rolling noise
Rolling noise is the most common type of railway noise and there are many technical
measures that reduce it. High levels of rolling noise arise from irregularities on the wheel
tread and rail head, called roughness. Roughness of the rails can be controlled by
maintenance grinding and can be further reduced by acoustic grinding. Acoustic grinding
requires that the rails are ground or polished as soon as a certain reference noise level is
exceeded (1-3 dB(A)). The potential of acoustic grinding will increase if all train wheels are smooth as well. A large improvement in this field is expected from the homologation of LL braking blocks, which make retrofitting of freight vehicles a cost-effective option (8-10 dB(A)).

By application of rail dampers (0-3 dB(A)) and wheel dampers (0-2 dB(A)) a further noise reduction can be achieved. Rail dampers are applied in several countries. The noise reduction depends largely on the characteristics of the track system without rail dampers.

Promising developments for urban areas are low-close barriers, typically placed at only 1.70 m from the track with a height of 0.70-0.85 m. In certain cases low-close barriers are acoustically equivalent to much higher conventional barriers, their advantage being that they do not block the view. However, in view of safety issues with barriers placed that close to the traffic, to date only few countries have decided about homologation.

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