Demand-Adaptive Systems (DASs) offer demand responsive services within the framework of traditional scheduled bus transportation. A DAS bus line serves a set of compulsory stops according to a predefined schedule, which specifies the time windows associated with each stop. Passengers may issue requests for transportation involving optional stops, that induce detours in the vehicle route. The design of a DAS line is therefore a complex planning process that requires to select the compulsory stops and to determine the line master schedule in terms of a time window for each such stop. \ud
In this paper, we focus on determining the master schedule for a single DAS line. We propose a mathematical description and a solution method based on probabilistic approximations of several DAS line core characteristics. Results of numerical experiments are also given and analyzed