How cellular models of urban systems work (1. theory)
Paul M. Torrens · 2000
urban-theoretical CA models, on the other hand, are used to examine the role that complexity has in driving dynamics in urban phenomena, such as fringe growth, redevelopment, suburban sprawl, edge city formation, polycentricity, agglomeration, inertia, diffusion, spatial structure, and social segregation. Essentially, abstract urban-theoretical CA models are used as laboratories for testing ideas and theories about the city (as opposed to complexity). Operational urban CA are used as planning support systems (although very few are actually operational) to assist planners, policymakers, and the public in managing and building cities. Generally, these serve as scenario-generating tools that form the basis of discussion. Operational urban models have increasingly turned to rule-based formulations based on logit models and decision theory (De la Barra 1989; Torrens 2000b). Also, in transport modeling, 48 activity-based simulations have been gaining ground (Ben-Akiva and Bowman 1998), and micro simulation with operational models has long been underway (Wegener 1996). It does not take a quantum leap to fuse those approaches with CA, which essentially add a dynamic and spatial spin to these existing techniques (Torrens 2000a, 2001). Indeed, following the development of the TRANSIMS model at Los Alamos National Laboratories (Nagel, Beckman and Barrett 1999), there has been a concerted drive to push metropolitan planning organizations into incorporating CA into operational forecasting models, with the implication that those models be used in the assessment of clean air legislation compliance (Travel Model Improvement Program 1999).