Firstly, you state in your email that: “such a [speed] reduction is unlikely to have any significant impact on the vibrations. Indeed, most of the trains already travel at 20mph on this section.” The report issued by TFL on 24th October (Reference: N&V-R2858) clearly states, using ATMS data: “The data shows trains speeds ranging between 29.3 and 42.13kph, or 18.2 and 26.2mph” and that “because small differences in train speed produce significant changes in vibration levels, the observed variability of VDV levels is easily explained by the different train speeds over the P&C”. The is clearly at odds with what you have said in your email. Its probable most trains are travelling faster than 20mph over the P&Cs and the report clearly states a strong relationship between train speed and VDV levels, with small differences in speed producing significant changes in vibration levels. So please can you provide the data to support your claim under the Freedom of Information Act. Furthermore, you state in your email: “Implementing such a restriction would be a very costly, complicated and long-winded process, as so many factors would be involved, including making changes to the local trackside signage and making amendments to the signalling system” Again, under the Freedom of Information Act I would like to request the following: • How long would it take to change the local trackside signage and what would that cost to do so? • Why does the signalling system need to be amended to implement the restriction, how long would it take to make such amendment and what is the cost of doing so? • What other actions would the process of implementing the restriction entail that makes it so complicated and long-winded? And how long would those actions take and at what cost? • What is the total cost of implementing the restriction? I have been corresponding with TFL about this issue for over 3 years now so implementation over a few months clearly would not bother me. Finally, you say in your email that: “I’ve had our engineers check the axle vibrations for the last three months, and they have confirmed that these have not increased” I would be grateful if you could provide this data on axle vibrations under the FOI Act. Please can you provide detailed answers to my questions above.

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TfL Ref: FOI-1988-2021

Thank you for your request received by Transport for London (TfL) on 4 January 2021, asking for information about speed restrictions and vibration data on the District Line.

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

• How long would it take to change the local trackside signage and what would that cost to do so?
• What other actions would the process of implementing the restriction entail that makes it so complicated and long-winded? And how long would those actions take and at what cost?
• What is the total cost of implementing the restriction?

We do not hold the requested information (and note that there is no obligation on public authorities to create new information in response to EIR requests). We have not implemented a permanent speed restriction at this location and therefore do not have the information you require.   

However, we estimate that for a permanent speed restrictions all day, the runtime would impact 6 million journeys a year, the disbenefits would be £75k per annum, equivalent to £20k lost revenue. For a temporary speed restrictions only during the off peak period, the disbenefits reduce by 40%. In addition, we are currently focused on the need to operate as many services as possible to enable social distancing.

While these numbers may sound small, they are significant. Ideally we would weigh up the journey time disbenefits against the monetised benefits for reducing the vibration. And because the number of people impacted by noise is relatively small in comparison to the number of journeys that would see their runtime increased, the case for reducing speeds and increasing journey times is not justified here.

• Why does the signalling system need to be amended to implement the restriction, how long would it take to make such amendment and what is the cost of doing so?

Any permanent changes to the speed here would need to be recorded, added to the signalling design and route maps for train operators (including breaking profile diagram changes), and likely require changes to the design of the 4LM signalling design.

I would be grateful if you could provide this data on axle vibrations under the FOI Act.

Please find attached the axel vibration data for the last 3 months.

If you are considering submitting a further request please think carefully about whether the request is essential at this current time, as answering FOI/EIR requests will require the use of limited resources and the attention of staff who could be supporting other essential activity. Where requests are made, please note that our response time may be impacted by the current situation.

If this is not the information you are looking for, or if you are unable to access it for any 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 Management Team

General Counsel

Transport for London

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