The purpose of the paper is to analyse informal collaboration in the public transport sector. Two Swedish case studies, Living lab Uddevalla and Guidelines for Regional BRT are analysed and compared concerning what kind of learning occurred and what lessons regarding informal collaboration to draw from the two cases. For both cases the analysis indicates that individual, single loop learning is the most striking type of learning among the participants. The voluntary approach of the two cases has advantages and drawbacks. Advantages include that participants were truly interested in the issues of collaboration, which created energy and contributed to building trust. The main drawback identified was that in both cases the voluntary enthusiasm of the participants collided with the formal requirements of planning and decision making. This has stifled the possibility of the informal collaboration processes to induce change in prevailing practices.