1. What was the cost of developing the new TfL Go App? 2. What Air Filtration/Ventilation systems are deployed onboard TfL underground trains and London buses e.g. HEPA Filters? 3. What plans If any are there to upgrade these Air Filtration/Ventilation systems in the future?

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Our Ref: FOI-0751-2021 

 

Thank you for your request received on 5 August 2020 asking for information about the TfL Go App and air filtration systems. 

 

Your request has been considered under the requirements of the Freedom of Information Act 2000 and our information access policy. I can confirm that we do hold the information you require. 

 

1. What was the cost of developing the new TfL Go App? 

The TfL Go app was built in-house by our Technology & Data team. This team develops websites, apps and open data services and much of that work is interdependent.  

 

The specific costs associated with developing the iOS app over the last two years are estimated at £520k. 

 

2. What Air Filtration/Ventilation systems are deployed onboard TfL underground trains and London buses e.g. HEPA Filters? 

3. What plans If any are there to upgrade these Air Filtration/Ventilation systems in the future? 

 

As regards London Underground trains, our deep tube fleets have a wide range of ventilation system designs. All have pressure ventilation systems that either extract air from the carriage to atmosphere outside of the train allowing fresh air to replace the extracted air through natural ventilators (saloon vents, end door windows or through door pockets, etc.) or they take air from outside the train and force it into the carriage – again allowing air to pass out of the carriage through natural ventilators.  

 

There are two types of pressure ventilation systems in each carriage that are both controlled by a single thermostat – one system only operates when there is a traction energy supply available, the other system is fed by the batteries on the train so it is available at all times (this provides a minimum emergency ventilation level e.g. when trains are stalled in tunnels). There are no filters on any of these pressure ventilation systems, and we have no plans to add filters since it is not technically feasible to fit them and provide access for quick and easy replacement during maintenance due to a lack of available space. 

 

The new S Stock surface trains that operate on the Metropolitan, District, Circle and Hammersmith & City Lines have a modern heating, ventilation and air cooling (HVAC) system that refreshes air from outside the train and also recirculates localised cool air inside the train adjacent to the HVAC unit. This system has filters, and these have been designed so that they can be replaced during maintenance. In accordance with EN779, these are G3 course filters – non-woven thermally bonded polyester fibres. HEPA filters are a class H filter which we do not use. 

 

All of our drivers cabs have separate external ventilation/air conditioning systems which are not linked to the air in the passenger saloon areas – some of the air conditioning systems have filters but, again, these are not HEPA filters. These filters used to reduce the level of tunnel dust in the driving cabs. 

 

As regards buses, our fleet has a wide range of system designs. Some vehicles have dedicated air extraction systems; some vehicles use recirculated air for heating and air con; others again use external air or a mixture. There are generally separate systems for the driver and passenger saloon. 

 

Our specification has been updated following work completed in association with the pandemic to state that drivers’ HVAC systems can only be fed by external (fresh) air. We have modified approximately 1,800 vehicles in our fleet to this standard during the last three months, which means that our whole bus fleet is now compliant. We are reviewing the specification for the passenger saloon in light of the pandemic, but it should be noted that this area benefits from regular door openings and windows that open and is of course a less confined area than the driver’s cab. 

 

If this is not the information you are looking for, please do not hesitate to contact me. 

 

The impact of current circumstances on TfL’s resources means we are not able to answer FOI requests readily and we ask that you please do not make a request to us at present. 

 

Answering FOI requests will require the use of limited resources and the attention of staff who could be supporting other essential activity. In any event, please note that our response time will be affected by the current situation. 

 

If you are not satisfied with this response please see the attached information sheet for details of your right to appeal. 

 

Yours sincerely  

 

Gemma Jacob 

Senior FOI Case Officer 

FOI Case Management Team 

General Counsel 

Transport for London 

 

[email protected] 

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