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