Ford Motor Company has been active in the analysis and implementation of Dial-A-Ride, a form of public transportation in which door-to-door service is provided with a fleet of small vehicles operating in a shared-riding mode. A Dial-A-Ride system design methodology has been developed, a task which has revealed the nature of the modeling process for complex transportation systems. This methodology has been used successfully to design Dial-A-Ride systems currently operating in several cities. A discussion of this process as applied to Dial-A-Ride research is presented here.Several stages in the modeling process are identified. The analyst's knowledge of the system, his information needs, and the modeling technique chosen to satisfy these needs are described for each stage. A city for which Dial-A-Ride has been proposed is analyzed to illustrate each stage in the design methodology.The effectiveness of an analysis which utilizes several types of models to examine a complex system such as Dial-A-Ride is discussed.