טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBroitman Dani
SubjectDynamics of Polycentric Urban Structure
DepartmentDepartment of Architecture and Town Planning
Supervisors Professor Daniel Czamanski
Professor Itzhak Benenson
Full Thesis textFull thesis text - English Version


Abstract

Classical urban models explain the spatial structure of an ideal mono-centric city assuming the pre-existence of a Central Business District (CBD). These models are driven by demand for geographic locations in proximity to the CBD. They lead to monotonically decreasing land rents and density as the distance from the CBD increases. However, modern cities can be considered to be mono-centric at a very crude geographic resolution only. Processes of urban growth typically give rise to a poly-centric structure. There is a growing body of evidence that urban spatial dynamics are discontinuous in space and non-uniform in time. Moreover, the speed of spatial expansions in some cities displays irregular patterns in different zones. The classical urban economics models are hard pressed to explain the formation of modern cities with polycentric structure and the dynamic processes that characterize them. Their inherent equilibrium based framework combined with a demand side focus, which ignores the supply side, is an impediment for understanding essentially dynamic processes.


Several factors are at the backdrop of polycentric urban evolution. Land developers’ choices in a context of spatial restrictions imposed by city planners lead to outcomes different than those forecasted by classical models. Attraction exerted by proximate, competing cities, combined with land development policies and developers’ behavior results in other types of urban development. In addition, assuming heterogeneous actors, such as developers with varying degrees of risk aversion, lead to complex urban spatial structures. The concept of characteristic time, defined as the period of time from the acquisition of initial property rights in the land by developers and until the first return on the investment is realized, captures spatial policy settings within which developers operate.


The set of models included here offers an explanation for the emergence of ideal polycentric cities and their associated dynamics. The models are focused on the supply side of the urban market and its interactions with city's planning policies. When it is possible and tractable, a comparative static's approach is presented.  However, most of the analysis is by means of agent-based modeling approach. The research demonstrate that the adversarial interactions between real estate developers and makers of planning policies create out-of-equilibrium, non-linear urban dynamics characterized by sudden emergence of sub-centers. A hypothesis is proposed that at the urban scale, the complex dynamics that emerge in the models cause patterns similar to those created by Self Organizing Criticality models, studied extensively in the exact sciences.