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Dutch cities are secretly tracking people’s phones to gather data on visitors’ behaviour

For city governments, information about how visitors behave is precious – and one Dutch company thinks it’s struck gold. Amsterdam-based CityTraffic (slogan: “We know where people go”) says it can measure how many people are in specific streets at any given time, accurate to half-hour time slots, and can determine how visitors travel through cities or shopping centres. It knows how long people visit for, and how often they return.

Thirty Dutch cities including Amsterdam, Rotterdam and The Hague have already hired CityTraffic to gain an insight in their visitor flows. In Rotterdam, 26 measuring points are used to be able to determine the exact routes visitors follow. The city also tests the efficacy of various measures to retain visitors. This has, for instance, led them to place monkey bars in front of the Markthall covered markets: keeping the kids entertained allows parents to stay and shop for longer.

But there’s one caveat to this data goldmine: CityTraffic gathers its information by tracking people’s phones.

CityTraffic can find devices where either Bluetooth or WiFi is enabled. It saves their unique identifiers, which are called mac-addresses, to a database, enabling them to track the device and with it, its owner.

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The firm says this data is completely anonymised, because the saved addresses are encrypted and never sent to clients: this way, it says, it can never be traced back to any individual.

But the Dutch privacy watchdog AP is not satisfied. Visitors should be informed when they are tracked, the watchdog said in a statement to news website RTL Z. They also shouldn’t be tracked 24/7, but only during peak hours. AP also says it might investigate CityTraffics data collection practices.


The city of Utrecht is positively angry: in its city centre, CityTraffic has been performing visitor counts without the knowledge or permission of the local government. The city council now says it will be investigating the company.

Opponents do have a point. There is something inherently creepy about a company tracking your phone when you’re out shopping, and selling this data on. And anonymised data is problematic: even if identifying characteristics are removed, it’s usually surprisingly easy to re-identify individuals. Research performed at MIT last year showed that 90 per cent of anonymised credit card transactions could be traced back to individual costumers.

Just consider how often you connect your phone to public WiFi-networks, which may or may not be secure. The data needed to identify you by your mac-address is almost certainly out there. And with CityTraffic performing 36m scans every year in Rotterdam alone, the company is collecting a lot of data.

But CityTraffic argues it’s just using a technologically more advanced method of counting people. Founder Huib Lubbers told RTL Z, “I understand the concern about WiFi tracking. But at CityTraffic we’re clear and transparent about what we do and which data we store. Many companies and cities profit from our data.”

The information the firm collects is certainly interesting. It’s shown, for instance, that shopping centres perform better if they contain a supermarket. City centres, meanwhile, are more attractive if they contain small shops as well as other attractions like cafes, restaurants and a cinema.

And there’s another thing worth remembering about privacy concerns: at least with CityTraffic, you know that the people tracking you mostly have good intentions. People or organisations with more malicious goals could be doing the same, and you’d never find out. The technology needed to track and log phones isn’t particularly sophisticated: any WiFi-enabled laptop can do it. So you’re never really sure if your phone is being tracked, by CityTraffic or by someone else.

Luckily, the solution is simple: switching off your WiFi and Bluetooth makes it impossible for CityTraffic to track you. They also offer an opt-out form on their website. But if you’re going on a super-secret shopping mission, it might be best to simply leave your phone at home.
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