on transit-oriented development (tod) and the criteria for determining tod centers: the case of shiraz metro line i

the current status and quality of urban and regional development has been criticized by many academics and professionals in different fields. at city centers in addition to traffic congestion, population growth, urban and regional sprawl and suburbanization have resulted in unsustainable conditions in many cities all around the world. in this regard, different aspects of urban form, especially the transportation and its mutual interaction with the urban and regional form, have been paid more attention. therefore, too much emphasis is currently placed on land-use planning as a means toward transportation policies and vice versa. also, the new generation of transit systems has revealed the powerful role of transit investments in changing the urban and regional forms. transit-oriented development (t.o.d) is claimed to be one of the most popular concepts that can fulfill this relationship. when the idea of transit-oriented development entered the lexicon of urban planning and design in the late 1980s, it was enthusiastically endorsed by some planners, designers and academics who viewed tod as a means of redressing a number of problems, including traffic congestion, air pollution, and incessant regional and urban sprawl. however, although many projects have been defined under this topic and many transit systems and communities around the world have participated in tod programs, but there is no agreement on its definition. generally, tod is explained as the development focusing around transit facilities and aim to improve accessibility, support community, enhance the quality of life at a regional scale, and support the financial success of transit investment. these explanations are apparently too general to represent an analytical framework of this concept. in addition to the examination of the concept of tod through the existing literature, the present article examines other relevant concepts like regional city and the patterns of urban form-transportation relationship in order to view tod from a different perspective. according to the regional city and tod literatures, tod is a strategy for creating changes in regional scales through the establishment of tod centers for obtaining sustainability goals such as increasing transit ridership, reducing reliance on the private automobile, improving walkable spaces and preserving the natural resources. considering the patterns of urban form-transportation relationship, four patterns have been explained, including adaptive transit, adaptive cities, hybrids and strong-core cities; it has also been emphasized that tod acts in adaptive cities framework. in this article, therefore, tod is defined as a strategy in adaptive cities framework that through the creation of changes in regional and urban physical forms and functional structures by establishing tod centers along transit lines, which helps obtain the sustainability goals. this can be used as an analytical framework of tod. investigating for criteria to designate the tod centers in transit lines, the degree of development and urban location are recommended and examined in shiraz metro line ?. also, these criteria help analyze the transit line and stations in relation to urban form.