Systems of systems arise when independently owned, operated and developed systems can achieve mutual benefits by working together. In collaborative systems of systems, there is no directing entity that instructs others how and when to collaborate. Instead, the collaboration relies on independent decisions by the constituent systems to form collaborating constellations, and the benefits are emergent properties of this. In this paper, we describe a design method for engineering collaborative systems of systems. We apply the method to the design of a collaborative system of systems for mobility in a rural setting close to an urban area and to truck platooning.