DUSSELDORF, Germany — CityLab reported on an app, called WelectGo, which allowed users in Dusseldorf, Germany to download a transit token in the form of a QR code that is valid for a single journey worth $2.80 after they select and watch four 20-second ads on their smartphone.

The app’s creators estimated they’d get roughly 1,000 downloads by the end of this year, however, after just one month, they exceeded 20,000 users. Expecting a lower take-up rate, Welect only launched with four advertisements. Without much revenue to buy them with, the supply of transit tickets ended up running out quicker than expected.

Welect could still possibly salvage the app, by getting more advertisers, requiring the user to watch more footage, or charging for each app download. Media reports suggest that they’re also planning to expand the app to other cities. For the full story, click here.