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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 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.
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
- 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 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.