Noise and vibration

The International Union of Railways (UIC), through its Noise and Vibration Sector (NV), works with its members to better understand noise-generating mechanisms in order to make tangible progress towards a being a better neighbour. The vision of the UIC NV Sector is to provide a global dialogue to integrate sustainability into railway operations and maintenance with a common goal to better manage noise emissions.

The UIC Low-Cost Noise Control by Optimised Rail Pad (LOWNOISEPAD) project, supported by the UIC NV sector, has brought together the railway community in an effort to find an optimal rail pad to help tackle noise issues across 12 different European railway networks. Within the framework of the project, measurement guidelines for railway noise were developed, which include advice on the measurement of noise-related track characteristics such as pass-by noise emissions, rail vibrations and decay rate on tracks (TDR). The drafted guidelines can be used for measuring the influence of noise with the change of track components. The IRS brings together expertise from the UIC members participating in the LOWNOISEPAD project, during which the guidelines were written and approved.

The guidelines are designed for infrastructure managers (IMs) and consultants carrying out measurements along the track. The guidelines ensure that noise measurements are undertaken so that they give comparable and repeatable results. The approval of the IRS was completed within the framework of the UIC Sustainability Platform and with the support of the UIC NV sector members. The necessary information was shared with other relevant UIC working groups under the Rail system department.

Through the IRS, UIC aims to provide its members with several advantages, as outlined below:

• The results are not only based on noise emissions but rail dynamic responses (e.g., rail displacements and accelerations) and decay rate on tracks are also measured at the same time, which enables the noise measurements to be validated.
• By following this methodology, infrastructure managers can more easily use the software tool created by the LOWNOISEPAD project to estimate the effect of new optimised rail pads on noise based on TDR measurements.
• New data measured following these guidelines can be used to improve the software tool.

It integrates in full or in part the following UIC leaflets:

• none

It aims to complement the following standards:

1. EN 15461:2008+A1-2010: Railway applications - Noise emission - Characterisation of the dynamic properties of track sections for pass-by noise measurements
2. EN 15610:2019: Railway applications - Acoustics - Rail and wheel roughness measurement related to noise generation
3. ISO 3095:2013: Acoustics - Railway applications - Measurement of noise emitted by rail-bound vehicles

Author UIC
ISBN 978-2-7461-3273-3
Pages 36

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 railhead, called roughness. The 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 makes retrofitting 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)), 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 a few countries have decided about homologation.

The study reviews noise mitigation measures for rail infrastructure in Europe, focusing on cost efficiency. It compares vehicle-related measures (like brake shoe retrofitting), track-related measures (like rail dampers), propagation path measures (like noise barriers), and receiver measures (like double glazing). The study confirms that rail freight retrofitting is the most cost-effective option, updating previous findings from the STAIRRS project with current data and life cycle cost assessments. Despite challenges in obtaining detailed cost data, the study reaffirms that retrofitting remains the preferred strategy for noise reduction.

Freight trains are the main source of noise on mixed railway lines. The UIC proposes retrofitting the European freight fleet by replacing cast iron brake blocks with composite ones to reduce noise. Financial support for this program depends on the noise reduction benefits. Over the past decade, numerous field tests have assessed the feasibility, economic, and safety implications of retrofitting, with some including noise measurements.

The study analyzed data from over 120 reports, normalizing noise data to standard track conditions (CEN ISO 3095). Results showed consistent noise reductions with composite brake blocks, achieving reductions of 7 to 12 dB(A) depending on the block type. This reduction allows for significantly more trains to operate within the same noise limits. However, actual reductions vary with track quality, being less effective on rougher tracks and more effective on smoother ones.

The report explores various noise mitigation options for railways, highlighting both widely used methods like noise barriers and more controversial ones such as rail dampers, acoustic rail grinding, and low-height noise barriers. Due to limited testing opportunities, the UIC Network Noise collected data and experiences from different countries on these measures. The report details the basics of noise control, explains the controversial methods, and summarizes the collected experiences and feedback from UIC members and other European representatives. The information was gathered through requests sent in 2011 and 2012, with additional results from other sources.

The European Directive on Environmental Noise, in effect since 2002, requires Member States to create public noise maps for major transport infrastructures and urban areas, assessing citizens’ exposure to harmful noise. Action Plans must be developed to reduce excessive noise and protect quieter areas, with public consultation. The European Commission reviewed the Directive in 2010 and proposed improvements, leading to a public consultation in 2012. The railway sector aims to ensure fair competition with other transport modes, internalize external costs, and maintain its environmentally friendly image. Key issues include the Directive’s exclusion of certain transport modes and the need for better noise annoyance assessments. The railway sector also advocates for stricter noise limits for road vehicles and warns against overly restrictive night-time noise limits.

UIC Project, Exploring bearable noise limits and emission ceilings for the railways: Part 1 - National and European legislation and analysis of different noise limit systems - 2011

The question ‘What are bearable limits for environmental railway noise?’ is discussed regularly in different forums at both National and European levels. To inform this debate, UIC has commissioned dB Vision to perform a systematic evaluation of all aspects affecting what is ‘bearable’. This allows UIC to propose, for the first time, a well balanced noise limit considering the interests of lineside residents and also what is feasible for the railways.

The findings are presented in a two-part report titled ‘Bearable noise limits and emission ceilings for the railways’. Please click below to download the reports.

This study demonstrates that:

• Railway noise reception limits should not be set lower than 55 dB Lnight
• Below 55 dB Lnight it is more cost-effective to mitigate road traffic noise
• Reductions below 50 dB Lnight incur large costs with diminishing returns
• Achieving the WHO night noise guideline of 40 dB Lnight would result in high costs and a massive impact on transport and the spatial environment.

UIC Project, Exploring bearable noise limits and emission ceilings for the railways: Part 2 - Cost and benefit study for different noise limits - 2011

The question ‘What are bearable limits for environmental railway noise?’ is discussed regularly in different forums at both National and European levels. To inform this debate, UIC has commissioned dB Vision to perform a systematic evaluation of all aspects affecting what is ‘bearable’. This allows UIC to propose, for the first time, a well balanced noise limit considering the interests of lineside residents and also what is feasible for the railways.
The findings are presented in a two-part report titled ‘Bearable noise limits and emission ceilings for the railways’. Please click below to download the reports.

This study clearly demonstrates that:

• Railway noise reception limits should not be set lower than 55 dB Lnight
• Below 55 dB Lnight it is more cost-effective to mitigate road traffic noise
• Reductions below 50 dB Lnight incur large costs with diminishing returns

Achieving the WHO night noise guideline of 40 dB Lnight would result in high costs and a massive impact on transport and the spatial environment.

When people are exposed to environmental noise, a range of adverse effects may occur. In case of excessive or incidental noise, people tend to complain. In daily life, people can be disturbed in their activities, such as working, communicating or sleeping. In the long turn, these effects may cause annoyance. Annoyance could affect health, because it may lead to irregular hormone secretion, stress, high blood pressure and cardiovascular problems.

Excessive noise during the night may disturb healthy sleep patterns and could lead to awakenings.