I am student journalist. I was looking to get more information about the noise made by tube trains. 1. What are the loudest tube lines? 2. What is the source of the piercing noise from trains? 3. Have you thought of any solutions to deal with the issue? 4. Have you received any complaints about the noise?

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Our ref: FOI-4931-1718

Thank you for your request received by Transport for London (TfL) on 19 March 2018.

Your request has been considered in accordance with the requirements of the Freedom of Information Act and our information access policy. I can confirm we hold some of the information you require. You asked:

1. What are the loudest tube lines?

    

    

   Unfortunately, we do not hold this information.

    

    

2. What is the source of the piercing noise from trains?

    

    

   The piercing noise (squeal) which comes from trains can have a variety of sources, however the most common source is the wheel-rail interface. Alternatively, squeal noise can also be generated by other mechanical or pneumatic parts of the train.

    

    

   Noise produced at the wheel-rail interface can occur for a number of reasons:

    

    

• Due to frictional contact between the inside face of the rail head and the flange of the wheel. This is mitigated against through the use of track-mounted lubricators, which reduce the level of friction between inside face of the rail head and the flange of the wheel.

   

• The build-up of vibration on the train wheel as it interacts with the rail can cause the wheel to resonate. This is mitigated against through the use of friction modifier which changes the dynamic interaction at the wheel-rail contact patch, and reduces the level of noise produced.

   

• Due to the effect of a combination of high levels of rail roughness and a resilient track fastening system. Resilient track fastenings are installed where a localised increase in rail roughness occurs so as to mitigate against ground borne vibration. The side-effect of this ground borne vibration reduction technique can be an increase in airborne vibrations, characteristic of squeal noise. To limit this issue, we only install the resilient track fastening system in particular circumstances. Analysis of in-cab readings taken over areas with resilient track fastenings and high levels of rail roughness do not show any danger of hearing loss.

   

   

1. Have you thought of any solutions to deal with the issue?

TfL’s Track Engineering team is looking into mitigation measures to address airborne noise produced across the network, having already carried out an industry first rail dampening trial to convert vibrations from trains into heat rather than soundwaves, which would reduce noise.

Measures are often bespoke solutions by nature of the complexity of the noise issues occurring, requiring extensive testing and assessment to ensure they are safe to install on the operational railway.

We are currently exploring the use of rail dampeners at selected locations which aim to minimise airborne noise in tunnels. Additionally, noise barriers on surface sections of the network are being explored, however, this will have to be done at a case by case approach due to significant cost implications.

Our Track Engineering team also carry out rail grinding and introducing ‎new resilient track fastenings and shock absorbent fixings, which‎ help reduce the sound when the trains run over them.

4. Have you received any complaints about the noise?

We do receive noise complaints and have a framework in place to ensure they are managed on a case by case basis. Where residents experience noise, we ensure we have done everything technically practicable to reduce the noise causing the complaint, however there are multiple sites where current technology and the age of the track mean that noise reduction is not possible. We are working with suppliers and academia to address these sites but it remains and ongoing challenge. Where it is practicable to reduce noise, we do – and we have reduced the noise for hundreds of properties affected by rail noise.

If this is not the information you are looking for, or if you are unable to access it for some reason, please do not hesitate to contact me.

Please see the attached information sheet for details of your right to appeal as well as information on copyright and what to do if you would like to re-use any of the information we have disclosed.

Yours sincerely

Eva Hextall

FOI Case Officer

FOI Case Management Team

General Counsel

Transport for London

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