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The Koopmans and Beckmann assignment model approach to problems of urban economics has led to considerable discussion. In our recent papers some of the issues raised were reviewed and also extensions that resolve many of the dilemmas suggested by the original model were proposed. Most of the approaches surveyed in our previous paper make little use of the duality properties of the assignment model. In the present paper it is argued that, under certain circumstances, dual variables interpretable as site rents and other dual variables that suggest the values of transferable development rights (TDRs) appear with model solutions. This view enhances the importance of assignment models to city planners and sheds light on how planners can guide optimal development along with the implementation of TDR policies.

Models that represent the polycentric and dispersed nature of modern cities should be able to account for the rise and fall of subcenters. Based on a review of the programming models applied to urban analysis, five properties are suggested that an adequate model should include. It should: 1 confront the simultaneity between markets for land and transportation services; 2 accommodate the reality of cities as places where externalities and common properties abound; 3 emulate the intertemporal albeit bounded nature of planning and decisionmaking; 4 fully exploit principles of economic theory; and, 5 offer computability. We develop a discrete programming model with these five properties, comparing its capabilities with those of previous approaches.

A general equilibrium, linear programming land-use model formulated in the heritage of Edwin Mills is extended to include a profit-maximizing objective function. This analog of the existing, cost-minimizing formulations in the literature is driven by exogenous export prices rather than by minimum-export requirements. It is demonstrated that the absence of minimum-export constraints results in an optimum corresponding to the exclusive export of the most profitable good. In addition, the outputs of the model are shown to be arbitrarily dependent on assumptions about zone geometry if export prices are high. A static, spatially disaggregate version of the model is specified by means of hexagonal land-use zones. Perfect market conditions are assumed and spatial markets identified. Production technologies are of the fixed-coefficient type with constant returns to scale. Import flows are treated explicitly for the first time in a model of this class, and their inclusion is shown to have a significant impact on optimal land-use configurations.

This book develops a national economic impact model to estimate the effects of simulated terrorist attacks and natural disasters on individual US States and economic sectors. The model, called NIEMO (The National Interstate Economic Model) looks at interindustry relationships and interregional trade. It is highly disaggregated making the model very accurate. The authors examine potential attack targets including theme parks, sporting events, bridges and tunnels in the national highway system as well as attempts to shoot down airplanes or spread foot-and-mouth disease. Covered natural disasters

In this paper we apply the theory of linear associative memories in producing initial parameter estimates for nonlinear iterative approaches. We also propose the use of FEED (Fast and Efficient Evaluation of Derivatives) to evaluate partial derivatives of functions encountered in nonlinear estimation. Suggested methods are presented in the context of calibrating spatial interaction models and are illustrated through numerical examples.