Studies of the process of model formulation by experts have shown the process to be an iterative one, in which the model is continuously refined until a complete and consistent representation emerges. It is also a highly unstable activity as the problem specifications, including the goal, may...

Some very fast least-squares based calibration procedures for the gravity model have been presented in earlier papers. Since these procedures are inconvenient or impossible to use when diagonal elements of the base period origin - destination (O - D) matrix are unavailable, one of the procedures...