November 25, 2016 | Ed Johnson-Williams

TfL needs to give passengers the full picture on WiFi collection scheme

Transport for London is running a trial that uses people's mobile phones to track crowd movement around 54 London Underground stations. We think they have to do a better job of communicating to passengers what the trial is, what the data will be used for, and how people can opt out.

When a device has WiFi turned on, it broadcasts a unique identifier called a MAC address. By tracking where they detect the MAC addresses of potentially millions of people’s devices a day, TFL want to analyse crowding and travel patterns to improve their services. TfL say they are not identifying individuals or monitoring browsing activity.

TfL WiFi data collection sign

TfL are alerting to passengers to the scheme with this sign. (Text of the sign at the end of this blog.)

Unfortunately, it misses three crucial points to help passengers understand a) how the scheme works, b) all the purposes the data is being collected for, and c) how to opt out.

  1. TfL are tracking people's movement around London and around stations
  2. Passengers have to turn off WiFi on all the devices they are carrying to opt out. If they leave WiFi switched on but never use the WiFi network, they will still be tracked.
  3. The data will be used to find and set prices for advertising spaces in stations, in addition to improving services

How to complain

If you don't like this and want to complain, you can complain directly to TfL using Facebook, Twitter or email.

Contact TfL on FacebookContact TfL on TwitterEmail TfL

Tell TfL to ensure they they properly inform passengers:

  • about how the scheme works and what they'll use the data for;
  • that passengers need to disable WiFi on all their devices to opt out.

The Information Commissioner’s Office (ICO) guidance on on WiFi location analytics says that:

  • "Clear and prominent information is one way to alert individuals that certain processing is taking place."
  • "The information should clearly define...the defined purposes of the processing"
  • "Data controllers should consider the use of:
    • signage at the entrance to the collection area;
    • reminder information throughout the location where data is being collected;
    • information on their websites and in any sign-up or portal page of the Wi-Fi network they may be providing; and
    • detailed information to explain how individuals can control the collection of personal data using the settings on their device."

We will be asking the ICO for its view on the signage used by TfL to alert passengers to this scheme and whether it meets this guidance. We have already contacted TfL with the points made here.

There are a number of other issues with the way TfL has implemented this scheme.

It is very difficult for passengers to find out about the scheme beyond the limited information on TfL’s sign. The sign provides a link to which is the Privacy Policy for the TfL website rather than their page about the WiFi data collection scheme. On a mobile screen - which nearly all passengers will be using in a station - the link to the page about the scheme is at the far bottom of the page. This is the page which includes all the details about what the data is being used for and how to opt out. It seems unlikely that many people will actually read this information.

Even if passengers turn off WiFi on their phone in an attempt to opt out, TfL may still track them using the MAC address broadcasted by tablets or laptops they are carrying. Many tablets and laptops, including Apple iPads and Macbooks, broadcast a MAC address when WiFi is enabled - even when the devices are in Sleep mode. While people may be able to easily disable WiFi on their phone, people will find it much harder to turn off WiFi on their laptop in a busy Tube station and so find it hard to opt out.

It is not clear that passengers are alerted soon enough or often enough about the scheme. The signs at London Bridge Underground station are placed near the ticket barriers. They were not placed at the entrances to the station or throughout the station. London Bridge is only one of the 54 stations which are part of the study and signs may be placed differently in other stations.

Passengers will be within range of TfL’s WiFi quite some way before seeing the signs and may not see the signs in the crowded ticket barrier area. Travellers who enter the Underground at a station which isn't part of the scheme will be unlikely to see a sign and TfL may collect data about them without having informed them about the scheme.

To alleviate some of these issues, we would like TfL to:

  • ensure they inform all passengers about the scheme
  • inform passengers of all the purposes this data will be used for
  • tell passengers to turn off WiFi on all the devices they are carrying if they want to opt out of the scheme
  • ensure signs are placed at the entrances to stations and throughout the stations

ORG has previously warned of the privacy risks of TfL’s Oyster card system. Although the data in this new scheme is not linked to data in the Oyster system, it is clear that TfL has not lost its appetite for monitoring passengers.

Text of TfL's sign

WiFi data collection

We are collecting WiFi data at this station to test how it can be used to improve our services, provide better travel information and help prioritise investment.

We will not identify individuals or monitor browsing activity.

We will collect data between Monday 21 November and Monday 19 December

For more information visit:

Comments (14)

  1. Teresa:
    Nov 25, 2016 at 03:16 PM

    Typical scaremongering again!!! This is happening everywhere from shopping centres to airports.

    You are moaning about the posters, why not worry about the companies doing this without posters or informing customers?

  2. Jim Killock:
    Nov 25, 2016 at 04:02 PM

    We do have to choose our targets. TFL's tracking is enormous in this case, covering people moving around a vast city. That makes their omission particularly serious. Also, as a public authority they ought to hold themselves up to the highest standards and set an example. Nevertheless, we would be very interested to investigate some of the examples you mention as well.

  3. Steve Ward:
    Nov 25, 2016 at 04:04 PM

    What is interesting is that TfL are announcing that this is happening - many organisations and locations probably do this with no notification. It's difficult to know what can be done about this as many devices have WiFi enabled automatically and silently. I am more conerned about who has access to the data and how it is protected. If TfL only use it for the purposes that they claim then fine but the data could be used by others both for legal and illegal purposes.

  4. Teresa:
    Nov 28, 2016 at 07:40 PM

    Jim, I understand that but you didn't give me an answer or provide any rationale of your thinking. I am certainly not a supporter of TFL but they have posters and information on their website. Clearly this goes above and beyond ANY other organisation. Why criticise them, you should be recognising them for being transparent. I am VERY dissapointed by this article and Open Rights Group's stance on this.

  5. Jim Killock:
    Nov 29, 2016 at 01:13 PM

    Hi Teresa,

    I’m sorry that you are disappointed with us.

    Our rationale for highlighting TfL’s actions is:

    (1) They are a public organisation, so have a role in demonstrating what is acceptable and setting best practice. What they do informs other people to what they might need to do. If they get it wrong, other people will assume that it is ok.

    (2) Their actions affect the privacy of millions of customers directly on their daily journeys, which is particularly serious

    (3) They are are accountable to Assembly Members and the Mayor so ought be to willing to resolve this postively.

    We are not being, I think, overly critical, we have simply raised a problem we think they can fix and hope they can do so.

    This does not preclude us highlighting problems from other organisations at all. We would be really interested to hear about other abuses, especially ones that are more egregious. This is something we have thought about asking our local groups to do for instance.

  6. Teresa:
    Nov 29, 2016 at 06:12 PM

    Personally I feel your actions are wrong and are punishing an organisation for trying to comply with the relevant guidance. This is going to simply discourage other organisations to NOT be open and transparent and do this processing without informing individuals.
    Well done Open Rights Group for giving organisations another reason NOT to do the right thing.

  7. Jim Killock:
    Nov 30, 2016 at 11:10 AM

    Hi Teresa

    We are not trying to punish TfL at all, we are very clear that they are taking good steps in their back end. On the transparency question, this is a very difficult problem as it is possible for organisations to disregard to ICO’s guidance altogether as you say.

    What the solution is to that is quite hard, as Wifi hotspots are in one sense entirely innocent, and tracking may or may not be a feature of their operation.

    Really, ORG is a very small cog in all this.Government organisations can play their part by setting an example, but the ICO’s enforcement of good standards including by investigations if abuse is suspected or known is what counts in the end.

  8. Andrew Beresford:
    Nov 30, 2016 at 03:26 PM

    I noticed a similar scheme was in operation at Manchester Airport recently. The signs explaining it were just a few tiny words on a sticker.

  9. Tony Clayton:
    Dec 01, 2016 at 12:04 PM

    I agree the criticism here is over the top. As someone in a rail user group and a frequent user of TfL services I would be more annoyed if TfL wasn't doing this. They need to know how people move around their stations, and as the information makes clear they don't know who is who, and could not tell you if you asked.
    With my rail user group hat on I spend too much time beating up rail companies for not knowing what is going on. I certainly won't complain about somebody making the effort.

  10. Timothy Dillan:
    Dec 02, 2016 at 07:52 PM

    TfL claim that the data will be anonymous as they will only be collecting MAC hardware addresses. If you happen to use this hardware iPhone, iWatch, Android, etc to pay contactlessly at the barriers will they not then hold a record of your mac address vs. your contactless account thus linking the two data sets?

  11. Headache:
    Dec 05, 2016 at 12:34 PM

    I personally feel that an email to all TFL customers explaining the purpose of the trial would be appreciated and actually set a helpful bar for other organisations (not sure if this has been done already and I am well aware that many organisations don't go as far as even providing a sign so this is not a targeted attack at TFL. I normally receive emails about maintenance/delays and so on; why not a courtesy email on data tracking and specifically how data will be analysed and potentially shared?). I don't believe that ORG are being over critical in this regard.

    To be clear, I am not opposed to tracking for traffic control in the underground but I do want to be properly informed about how the data is used and what types of third parties may be able to track me for the same reasons that I expect websites to explain how they use cookies to improve their services (whether these JUST use Google Analytics for example) and give Internet users a reasonably fair opportunity to opt out. I think TFL could do more and a sign is woefully insufficient.

    Until TFL are able to provide more details about the trial, I will disable my Wifi whilst on the move. Grateful for the article which highlighted the developments at TFL in the meantime.

  12. toby:
    Dec 07, 2016 at 06:03 PM

    Anyone know whether it's a legal requirement to communicate this? Are companies breaking any laws by tracking and not communicating?

  13. Matt:
    Dec 11, 2016 at 08:25 AM

    Teresa, Tony,

    What are your thoughts on the scope of TFLs coverage?

    I see them as the one organisation in London that can cover every inhabitant. This may be a bit dramatic but with the potential to put WiFi on buses it becomes every more relevant.