The purpose of the paper is to identify issues related to the two fundamental principles of traffic assignment and two techniques used for its solution. Firstly, the inter-relationships among the average, marginal total and integral forms of the travel time (cost)-flow function are discussed. The choice of the appropriate form of the travel time (cost)-flow function depends on the assignment technique (heuristic loading or mathematical optimisation) and the assignment principle (user-optimising or system-optimising) adopted for use. A table is given as an aid for this choice. A graphical explanation is then presented, based on the fundamental two-route single-demand assignment problem to illustrate the usefulness of the graphical approach for simple analysis of various issues related to traffic assignment.
AKÇELIK, R. (1979). A Graphical Explanation of the two Principles and two Techniques of Traffic Assignment. Transport Research Part A. General 01/1979;13(3): pp 179-184.