As a part of Greencarrier’s 15 year anniversary, STARK have branded 100 trams with four unique icons, turning  them into a part of the “Positive Challenge”. The Positive Challenge is a game uniquely for Greencarrier employees. A part of the challenge is to find four icons in the Gothenburg tram system. Other parts include tracing the company’s history throughout the city and to make strangers happy by random acts of kindness.