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NYC 9/11 Public Portal Document

6 major metropolitan area. The ease of such replication should be similar, say, to that of mode choice models, of the UTPS procedure or of transportation network assignment. Hence, it is highly desirable that models use readily available data sources, be easy to calibrate and test, and be relatively easy to operationalize on a mainframe or microcomputer. When such models are developed, they will close the gap between the needs of the transportation planner, who has traditionally been interested in forecasting physical trips and loads on the transport system, and the needs of the urban economist who is concerned with finding beneficial transport designs and policies that can be implemented in an urban area. Simply stated, transport planners will be equipped with the tools of cost-benefit analysis and will be able to predict not only the physical consequences of their policies and plans, but also the economic impacts of such actions.

One of the models developed in this study, NYREG, is such a regional-scale model. It is important to understand, however, that NYREG is not a "regional economy" model. A regional economy model would divide the region's economy into many sectors and would forecast the output, employment, and trade linkages among the sectors as well as such aggregate quantities as umemployment, regional GDP etc. By contrast, NYREG takes as given the geographic distribution of employment within the region and proceeds from that basis to model the travel and housing related decisions. A natural way to understand NYREG is to view it as an extension of the Urban Transportation Planning System (UTPS) which has been in use by transportation planners for many years. UTPS models households' travel decisions in an number of sequential steps. These are trip generation, trip distribution, modal split, and, finally, traffic assignment. The sequential nature of the UTPS has been criticized because of the well understood feedback effects among the different steps which are involved. Also, the UTPS does not consider the importance of using economic relationships to model the relationships at every step. Finally, UTPS does not include the working of the real estate markets and, therefore, is not suitable to predicting how real estate values will change in response to the travel decisions of individuals.

NYREG is a response to the above concerns. On the one hand, the sequential steps of the UTPS (trip generation, distribution and modal assignment) are unified into a simultaneous process by means of an economic model. On the other hand, travel decisions are unified with the housing related decisions so that the feedbacks between the two decisions can be captured. NYREG has been developed and calibrated for the New York Metropolitan Area. It is presented in detail in Chapter 2 of the

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