ESTRAUS: A COMPUTER PACKAGE FOR SOLVING SUPPLY-DEMAND EQUILIBRIUM PROBLEMS ON MULTIMODAL URBAN TRANSPORTATION NETWORKS WITH MULTIPLE USER CLASSES

In this paper we present a modeling approach for solving quite general supply-demand network equilibrium problems intrinsic to the transportation planning process. The software implementation of the model described herein is known as ESTRAUS. It is significant that ESTRAUS is unique among commercial software for transportation planning because it implements all of the key theoretical and algorithmic advances in static traffic assignment and planning that have appeared in the literature during the last 20 years. In particular, ESTRAUS is able to consider a variety of demand models and trip assignment behaviors within the same model implementation including multiple user classes and combined travel modes that interact on the same physical network. The demand choices are supposed to have a hierarchical structure. When the trip distribution is variable, a doubly constrained entropy-maximizing model is considered at the first level of choice and a hierarchical logit model is used for the remaining demand choices (time of departure, mode choice, transfer point for combined modes, etc.). If the trip distribution is considered to be exogenous, the demand choices are modeled with a hierarchical logit. One of the model’s main features is that it considers the effects of congestion on the road network as well as in each public transportation service network. Different problems are mathematically formulated as variational inequalities, with asymmetric cost functions, and all of them are solved following the diagonalization algorithm. Each iteration of the aforementioned procedure solves an optimization problem using Evan’s algorithm. One of the mathematical formulations presented in this paper (distribution-modal split-assignment) has been implemented in the latest version of the computer model ESTRAUS, which is part of a battery of planning tools developed by the government of Chile to simulate the operation of alternative network configurations and evaluate strategic development plans for urban transportation systems. In the last part of the paper, some applications of ESTRAUS developed in Chile during the last years are briefly discussed.

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