Request ID: FOI-0094-2425 Date published: 03 May 2024
You asked
To whom it may concern
Please provide following information regarding lights fitted in Bakerloo tube carriages as I have not been able to obtain this information from TFL complaints team as no-one knows:
-When (or over what time span if applicable) were the Bakerloo Line carriages upgraded with those new super bright blue/white, presumably LED, lights?
-What LUX levels (measure of lighting levels) are achieved within the Bakerloo Line carriages?
-What colour temperature is used (measured in Kelvin) in the Bakerloo line carriages?
-What is there reason for TFL to choose this blue/white over say a regular warm white light temperature for Bakerloo Line carriages?
-What minimum Lux level is TFL required to provide by law within the tube carriages?
-What or whom dictates the level of brightness TFL aspires to provide in their tube carriages? Is it reading newspapers or books, maybe knitting or any other manual activities?
I would appreciate a quick response as I raised some of those points initially with a complaint to TFL on 7th February 2024, but have not named to receive any satisfactory responses so far....
Please confirm receipt and advise by when I am likely to receive the answers to my queries.
We answered
Our ref: FOI-0094-2425/GH
Thank you for your request received by Transport for London (TfL) on 9 April 2024 asking for information about Bakerloo tube carriage lighting.
Your request has been considered under the requirements of the Environmental Information Regulations and our information access policy. I can confirm that we do hold the information you require.
-When (or over what time span if applicable) were the Bakerloo Line carriages upgraded with those new super bright blue/white, presumably LED, lights? The installation started in 2021 and was completed in April 2024.
-What LUX levels (measure of lighting levels) are achieved within the Bakerloo Line carriages? The average rated level of luminance registered was 471 Lux, this is noted as being <5% over the maximum levels stipulated in the relevant BS standard below, however this has been justified as there is an expected degradation in performance over the life of the fittings and this high starting point ensures we meet the minimum requirements at end of life, which is expected to be 10 years.
The system has been designed in accordance with LU standards which are derived from BS EN 13272-2:2019 - Railway applications. Electrical lighting for rolling stock in public transport systems - Urban rail
The design shall take account of aging and pollution of light sources and luminaires. The rated illumination shall be multiplied by 1.25 (equivalent to a light loss factor of 0.8). For seated and standing passengers the average rated level of luminance shall be greater than 350 Lx and not more than 450 Lux with a level of uniformity as defined in BS EN 13272 for mass transit vehicles
-What colour temperature is used (measured in Kelvin) in the Bakerloo line carriages? The temperature is 4000K
BS EN 13272 states “The correlated colour temperature of the lamps used for general lighting shall be between 2800 K and 7000 K. NOTE 1 For reasons of visual comfort, colour temperatures above 5000 K are not advisable”.
-What is there reason for TFL to choose this blue/white over say a regular warm white light temperature for Bakerloo Line carriages? The LEDs are not actually all of one colour frequency – LED manufacture (silicon processing) is not exact in this way; each LED manufactured will have a slightly different frequency output. The manufactured LEDs are sorted into ‘bins’ which are of a defined frequency range. As part of the design phase we adopted common industry best practice (to ensure frequency uniformity of the light output achieved) and asked the supplier to provide a design solution that had a 3-bin range, thereby defining a limit around the desired design frequency. The supplier, who researched the market on TfL’s behalf, concluded that it was not possible to source the required LEDs to meet this tolerance requirement and achieve a 3000k nominal design. For this reason, a 4000k nominal was chosen for the design.
For background, historically fluorescent tubes with a colour temperature of between 3000k-5000k have been used on London Underground rolling stock. The adoption of an LED lighting solution that uses 4000k aligns TfL with what is more commonly used on European Rolling Stock which makes it easier and cheaper for us to source lighting solutions. It is worth noting that the rail vehicle market is quite niche and many of the more commonly available industrial LED products will not meet or have not been tested to ensure they meet the standards required for use on rail vehicles.
-What minimum Lux level is TFL required to provide by law within the tube carriages? There is no legal limit that dictates the lighting levels that TfL must provide within their passenger train environment. We are, however, committed to providing a pleasant ambience for our customers and have an obligation to ensure that our all our customers are safe when travelling on our network. For that reason, we ensure that minimum lighting levels are achieved in all likely events (including detrainment) and that key interfaces are provided with adequate light, such as passenger door thresholds, gangways and passenger emergency alarm handles. The minimum Lux level requirements vary depending on the particular event and the position within the saloon environment, so there isn’t just one figure that is applicable. The lighting level limits have been derived through years of experience, testing and on-boarding of best practice from across other industries.
-What or whom dictates the level of brightness TFL aspires to provide in their tube carriages? Is it reading newspapers or books, maybe knitting or any other manual activities? TfL works to its own internal standards for passenger rolling stock, which for saloon lighting are in sync with those of our other railway operators in the UK and Europe. Our engineers have had involvement in the development of standards that are used throughout the Rolling Stock industry and the limits which they apply for lighting (and other facets of Rolling Stock) have often been adopted as industry best practice. Our standards for Rolling Stock consider the lighting level for passengers in standing and sitting positions in standard operating conditions and requires minimum LUX levels to be achieved at a 45° plane (to the subject), which is representative of activities such as reading.
Please see the attached information sheet for details of your right to appeal.
Yours sincerely
Graham Hurt FOI Case Officer FOI Case Management Team General Counsel Transport for London
