This article puts forward the view that, for each transportation planning or management problem, there is a particular way to simultaneously define the multiple levels of procedures useful for the problem and set it in its proper perspective, the latter essentially by the identification of what is exogeneous and endogeneous to the problem at hand. The joint determination of these levels and of the exogeneous/endogeneous mix defines the two-dimensional frame of each problem. To develop their view, the authors extend our previous conceptual framework to include, in the first dimension, an activity location procedure, and to distinguish, in the second dimension, between operational, tactical, and strategic perspectives. They conclude by relativising the use of solution techniques by making them ancillary to the situation planning requirements.
