One day in Berlin, Google Maps showed the red line denoting bumper-to-bumper traffic on several ordinarily calm streets, even though there was no special event taking place. Or anything happening on those streets, actually. The culprit: one man slowly walking around the city pulling a red wagon.

Berlin artist Simon Weckert rented 99 Android smartphones, installed 99 sim cards in them and filled a wagon with them, all powered on and running Google Maps. He then took to the streets of Berlin with them at a time when traffic was sparse. The object of the experiment, which he conducted last summer, but just published yesterday for the 15th anniversary of Google Maps, was to show how much we rely on the app’s traffic technology despite its limitations. It also answers some questions we’ve probably all had about how Google Maps actually works.

Artist Simon Weckert walked around Berlin with 99 phones in a wagon

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

The way Google Maps estimates traffic is by assessing the density of phones that enable the app to access their location, confirmed a Google spokesperson. Therefore, to the app’s technology, the only explanation for Weckert’s 99 phones in a condensed space was a dense traffic jam. The spokesperson also said, somewhat creepily, that Weckert’s experiment helps Google figure out where its geolocation needs to improve. It can distinguish between the motions of a car and a motorcycle, apparently, but recognizing movement in a wagon is still beyond it.

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

Image credits: Simon Weckert

If you’re wondering why a bus full of people with smartphones doesn’t automatically show up as a traffic jam, a bus is very easy to recognize via geolocation, as such a cluster of users follows a predictable path and stops in predictable places. Maybe Weckert’s next experiment should be trying to fool Google Maps into thinking he’s a bus.

A video of the experiment shows how quiet the streets actually were during the “traffic jam”

Image credits: Simon Weckert

The question on everyone’s minds is why? Weckert wanted to show how we rely on data to predict reality for us so we can plan our actions around it, trusting it as an objective display of reality, even though the technology used to interpret data can err or be misled, potentially forming an inaccurate model. Commenters are already coming up with ideas for gaming the system based on his experiment, while others think it worked a little too well and could have dangerous consequences.

Not everyone sees the value of the experiment, but it gave some people ideas