A systematic review of the dimensions of transit-oriented urban planning and design

Due to valuable global experiences regarding Transit Oriented Development (TOD) as a context-sensitive strategy, updating the planning dimensions and even post-performance imperfections is inevitable by which reinforcing new urban plans could be dramatically pursued. Therefore, the present study aimed to highlight the most significant dimensions of transit-oriented urban planning all over the world. To this end, relevant qualitative studies were systematically reviewed through a Qualitative Meta-synthesis study. A total of 17 peer-reviewed articles and complementary databases searched during May-August 2018 led to a number of 6522 records among which 23 cases met the eligibility criteria and quality appraisal for inclusion in the final list. Then, the results were interpreted by using qualitative content analysis and a development-driven model was drawn by a classification as the general TOD planning themes including place development, policy development, process development, and sustainable development. Based on the results of the study, 30 planning dimensions pertinent to TOD were listed. The results helped retrieve and collect the up-to-date dimensions and interpret the changes appeared during the decades of planning. communities” , , , ,


Introduction
It is an article of faith that the idea was originally designed by Peter Calthorpe, an American architect in the U.S. His primary idea was formed based on the interaction between movement and urban form which was closely connected with development strategies such as Smart Growth and New Urbanism in notion (Xu, Guthrie, Fan, & Li, 2017;Dunphy & Porter, 2006).These strategies pinpoint providing a set of new urban settlements in order to recite the story of promotion against being dependent on the cars and its hostile impacts (Shibley, 1998;Goetz, 2013).In fact, after ample suburbanization and increased car-oriented movements during post World War II, more urban road construction and growing car travel demand led to congestion, energy shortage, negative societal outcomes, as well as the posed costs on people, cities, and the environment (Banister, 2005;Xu, Guthrie, Fan, & Li, 2017).Accordingly, high-quality public transit, as well as the high level of local accessibility was totally regarded in cities and placed on the agenda in order to decrease the need for car use.Investments on urban rail infrastructure with regard to new development around its station reshaped the future city structures once more.Therefore, the links between transport and land use and public policies established the basic fundamentals of the Transit-Oriented Development (TOD) concept in the United States (Aston, Currie, & Pavkova, 2016).However, different global communities have already applied various TOD proposals in their planning process (Xu, Guthrine, Fan, & Li, 2017).Staricco and Vitale Brovarone (2018) refer to TOD as "emerging European-style planning in the USA".For instance, proposals such as Garden city movement in the late 1890s (Hall, 2002), Linear city by Arturo Soria y Mata (Sung & Choi, 2017), Copenhagen finger plan in 1947 (Knowles R. K., 2012), Toronto in the 1950s (Kenworthy, 1991;Cervero, 1986), Stockholm master plan (1952), Development plan of Paris in 1965, Rosario Plan for Seoul in 1980 (Sung & Choi, 2017) have clearly paid attention to the instrument of movement and development integration in their general concepts.
On the theoretical side, modern TOD studies were practically initiated by the New urbanism idea in the 1980s in the U.S., and then the Calthorpe's seminal book appeared including the main idea.General principles, methodology development, implementation mechanism, the comparison of realworld successful previous cases were highlighted by a majority of primary studies for a few years (e.g., Cervero R., 1998;Boarnet & Crane, 1998;Calthorpe, 1993;Van der Ryn & Calthorpe, 1986;Freilich, 1998;Cervero R., 1986;Delsohn, 1989;Girling, 1993).In this regard, addressing the main challenges of American cities, as well as the advantages of the lessons related to integrated transport/land use in the framework of pedestrian pockets was emphasized to indicate a new trajectory for redesigning the urban areas.
Evaluation studies as the third type of TOD studies were developed when the years of TOD experiences provided new kinds of opportunities for and challenges against transit-oriented urban planning and design.In this sense, TOD output measures including travel behavior and the related indicators were diversely reassessed using different methods.Such indicators included VMT , ridership, trip length, travel distance, travel costs, car use and ownership, residential self-selection, mode choice (e.g., Chen et al., 2017;Ewing, Hamidi, & B Grace, 2016;Kamruzzaman et al., 2015;Haifeng Liao 2015;Zhang & Fujiwara 2009;Crowley, Shalaby, & Zarei, 2009;Yang & Pojani, 2017;Cervero R., 1994), as well as TOD-ness and typology (e.g., Lyu, Bertolini, & Pfeffer, 2016;Renne et al., 2016).In addition, this type of TOD study accompanied the appearance of new enthusiastic developing countries which sought a solution for mitigating their numerous urbanization-caused problems by grabbing the general ideas (e.g., Zhang M., 2007;Pongprasert & Kubota, 2017;Rangwala et al., 2014;Wey, 2015;Alwehab & Abdul Ghafoor Al-Ani, 2016;Gilat & Sussman, 2003;Babalik-Sutcliffe, 2013), leading to an agreement among TOD professionals in which TOD is a context-sensitive instrument in urban planning by which decisions and policies concerning transportation and development integration could vary for each community (DeVos, Van Acker, & Witlox, 2014;Tan, Bertolini, & Janssen-Jansen, 2014).
In general, a variety of these studies, in all kinds and periods, diversely discussed a set of dimensions as critical-neglected ones which have successful transit-oriented planning or as general prerequisites.Further, the diversity of studies in different contexts provides a number of academic and applied resources for testing and adapting in other urban contexts.In this sense, the growing number of developing countries as the newcomers tends to pursue TOD proposals while no explicit and up-to-date list of dimensions exists for testing by the other studies in different contexts.That is why the present study attempted to fill the gap by answering the question "What are essential dimensions for TOD planning as general prerequisites?".For this purpose, various aspects of urban planning and design for a community should be adaptively reconciled to TOD core idea, which ranged from socio-demographic, technical, financial, governmental and political, economic to environmental aspects.This trend has already been perused in global studies during the recent years.Although it may differ from one city to another in all of the above-mentioned aspects, previous studies and practical experiences can effectively provide a comprehensive database about the subject in order to generate the whole image of the dimensions.Therefore, the current study benefited from a systematic review approach to synthesize the findings of previous studies.After following several steps, the approach yielded a categorized list of dimensions for planning the TOD.All the steps are explained based on a meta-synthesis method.

Method: Framing a qualitative meta-synthesis (QMS)
Meta-synthesis as a qualitative and interpretive method originally arose from nursing and has been extensively applied in fields such as health, social work, along with organizational studies which focus on evidence-based policies and practice (e.g., Walsh & Downe, 2005;Kim, 2018).By a secondary analysis, this method structures a basis for future investigation and helps in understanding the progress of a discipline (Thorne & Paterson, 1998).Furthermore, it can be formed based on a new research question or technique which involves breaking down the results of other qualitative studies on a specific subject, examining their features, and finally, combining their results into an integrated body (Moeller, Copes, & Hochstetler, 2016;Bowman et al., 2018).
Although a limited number of studies have been conducted with respect to the urban issues, QMS can make a holistic reinterpretation for dealing with the ongoing urban issues.Additionally, the integrated transport and development in urban studies has been the subject of a large body of earlier research during recent decades.Different qualitative studies have attempted to draw definition, general principles, implications, as well as planning and the design dimensions of transitoriented Development (TOD) since 1990.The systematic review and meta-study are highly probable to withdraw up-to-date dimensions for transit-oriented planning.Employing QMS, the present study aimed to describe the integration paradigm in the framework of TOD by blending the study findings into the primary list of TOD proposals.A QMS study, formed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (Moher et al., 2009), can be categorized into a number of stages.

The meta-synthesis query and eligibility criteria
The QMS question is related to the overall aim of the research which seeks to present transitoriented dimensions of urban development.So, finding planning and design dimensions would be the primary concentration of this meta-study.Some criteria were needed to be predefined for including and excluding the studies related to the subject before initiating the search process.The resources were sorted into two general types (Figure 1).Concerning the inclusion criteria, English peer-reviewed qualitative studies were globally encompassed, which mainly emphasized TOD planning and design dimensions in their results and were published after 19901 .Conversely, quantitative studies published before the abovementioned date, as well as those only related to transport (or land use) were systematically excluded from the study.To include complementary resources, the grey literature including academic and institutional reports, guides, documents, and applied projects were the case in which TOD planning, design, and implementation dimensions were part of their proceeds.The incomplete records were not welcomed.

Information resources and systematic audit
A large number of studies have focused on the dimensions of transit-oriented urban planning and design since 1990.Academic studies, as well as practical institutional reports and development guides have already provided a set of fluent datasets.In fact, ignoring these experiences is not acceptable while relying only on routine journals and electronic database search.Therefore, other complementary resources including documents, applied reports, and guides were systematically reviewed during the process.
Totally, 12 articles and 5 complementary databases were queried in different disciplines ranging from urban studies to environmental science (Figure 2).Apart from routine search of electronic databases, the data were exclusively hand-searched through the related journals concerning similar Then, their titles and abstracts were screened manually.As regards the complementary resources, available electronic documents, published by well-known agencies and institutions and involved in transportation and development practice and studies such as ITDP 5 , Reconnecting America, CTOD 6 , VTPI 7 , NPA 8 , USHSR 9 , Smart Growth America, and APA 10 , were additionally reviewed to cover a wide variety of records containing the relevant data.
2 Development-oriented transit 3 Transit-adjacent development 4 Transit-joint development 5 The Institute for Source: Author

Literature Search
The keywords were collected by reviewing primary studies on transit oriented development (TOD) before starting the QMS process.In addition, a number of former related studies including the reviews were initially screened to choose and set appropriate keywords for the main search.Review studies provided considerable help to the author in this way.The searched terms included "transitoriented development", "pedestrian pocket", "transit village", "transit-oriented urban planning", "transit-oriented community", "transit-friendly design", "transit-supportive development", "transitbased development", "transit-rich development", "rail-oriented development", "traditional communities", "transit communities", "compact city", "smart growth", "new urbanism", and "landuse and transportation".The above-mentioned keywords included nearly other synonyms of TOD which were used in previous resources and somehow related to the concept of TOD.
Through a breathtaking search process, the keywords were then linked with "OR" aiming at obtaining a wider range of proper studies.However, using the Boolean operators was impossible in some complementary databases.Accordingly, each keyword was separately queried and then the results were summed together for obtaining the highest number of possible qualified records.All search and selection procedures were conducted during May-August 2018.

Studies selection procedure
Four-stage study exclusion reinforced the selection process (Figure 3) ranging from title screening to quality appraisal.Although 6522 records were identified surfing the databases and other complementary resources, the final list gradually decreased to 23 records and contained 20 peer-reviewed articles and three applied projects and reports.Further, the references and bibliography of the selected records were multiple screened for relevant studies before the quality appraisal.In this regard, the new records underwent all four phases of exclusion once more.As a result, a total of three records were added to the final list Furthermore, a qualified record was required to pass the quality appraisal for inclusion in the final list.It means that qualitative research should be judged for being convinced that quality studies are included to start off the synthesis process.In the current study, the 18-item method, presented by Spencer et al. (2003) and called "Framework for Assessing Qualitative Evaluations" was pursued to ensure the avoidance of bias risk and to obtain a set of qualified records to reach the valid proceeds.Therefore, among the 117 evaluated records, twenty-three records including twenty peer-reviewed articles and three complementary records met the essential quality.

Data extraction
The final included records were reviewed several times.At this stage, different sections of the studies such as the Results, Conclusions, Recommendations and Suggestions, Close, Epilogue, Discussions, Future research, Limitations, and Practical Implications were exclusively analyzed and then synthesized.Figure 4 summarizes the other data which were extracted in order to make an inter-study comparison.As shown, global studies were welcomed at the final list so that 10 studies were implemented in North America (10), South America (1), Europe (4), Asia (4), Australia (5), and Africa (1) with diverse scales were included ranging from the neighborhood to the country.However, some of these studies used no distinct case study and concentrate on the subject as a qualitative review or multi case-study.It is worth mentioning that diversified aims and methods form the foundation of the selected studies.

Data analysis and literature retrieval
Although diverse analysis approaches have been used so far, the present study followed the interpretative classic approach outlined in Noblit and Hare (1988), by which reading and rereading were emphasized to withdraw the main findings and classify the concepts and themes.Accordingly, the results of the studies were overviewed by a Qualitative Content Analysis.New concepts were derived based on translating and integrating explicit and implicit concepts as well.After categorizing through a comparison content analysis, similar contents generated themes and sub-themes based on the general concepts.

Results
Table 4 demonstrates the planning dimensions for TOD derived and sorted in themes and subthemes as the cardinal proceeds of QMS.Four development-driven themes were identified including "place development", "policy development", "process development", and "sustainable development"  Source: Author

Discussion and conclusion
Similar to other urban studies, an ample range of transit-oriented strategies connected to diverse multidisciplinary knowledge areas has provided a plenty of supportive studies during the recent decades.Further, it highlighted a vast range of dimensions to be considered when transitoriented development (TOD) planning action is on the agenda for the urban governments, some of which were most popular among TOD studies.For instance, nearly every record refers to at least one of the dimensions related to the individual area characteristics of the physical development (see Figure 5).Furthermore, coordinated interagency policy-making, institutional framework, interactor collaboration, community engagement, inclusiveness, and community income growth were considered among the high rate sub-dimensions in terms of the reference number.Newlyinterpreted concepts (i.e., dimensions and sub-dimensions), as well as former qualitative studies, motivated the author to categorize them in a development-driven model in which all of the investigated dimensions have been comprehensively covered so far.As illustrated in Figure 6, all of four TOD planning themes act together in a cycle in order to make it perfect.Developing a process tends to be crucial for implementing the idea by establishing transit-oriented plans and policies.In fact, the process helps to ground a set of transit-oriented places in which pedestrian-friendly environments are on the agenda.As a result, these places lead to more sustainable urban areas in terms of social equity, economic efficiency, and environmental quality, and more interestingly, the idea of sustainability again feeds the transit-oriented policy sides including both transit-and builtenvironment-oriented plan and policies.In fact, the cycle is initiated by setting a range of policies which are inspired by the idea of sustainability.Therefore, sustainability has several effects on and the strategies for transit-oriented urban planning and design.Additionally, a partly-inverse cycle can be observed in the inter-dimensions relationship by which the policy structure and transit-oriented processes tend to be subsequently redesigned through possible adaptions ahead over the procedure of TOD implementation.Among place, policy, process, and sustainability, the sustainability seems to be synthesized for the first time compared to other previous classifications.However, the new idea that planningspecific dimensions for TOD are synthesized and classified in the previous studies (e.g., Thomas & Bertolini, 2017) apparently tends to highlight the successful factors of TOD delivery.Social, environmental, and economic effects of and conditions for TOD planning could be assessed as a new trend in integrated studies.In the current study, screening different TOD studies demonstrated a shift from primary transit-oriented dimensions in order to develop the knowledge such as basic physical urban design characteristics to the second kind of dimensions arising from evaluation studies and other knowledge discipline.For instance, although the environmental quality is considered as a part of a fundamental long-term goal of strategies related to integrated transport and land use, it has increasingly attracted attention in recent studies (e.g., Cervero & Sullivan, 2011).
The local urban context and driving forces play a role in establishing the importance and priority of dimensions.For example, cities in the United States are attempting to facilitate implementation dimensions (i.e., process development) and financial mechanism while developing countries such as India, Malaysia, Vietnam, and some parts of eastern China seek for a set of policy transfer mechanisms and adopt the idea adaptively.Accordingly, post-performance (e.g., in the U.S.) versus pre-performance (e.g., in Iran) TOD dimension planning and design can be smartly distinguished in this regard, which is subject to further investigation.
The number and availability of the studies and databases may reflect the qualitative metasynthesis (QMS) process.However, systematic reviews are typically conducted by collaborative work among several researchers who simultaneously focus on the subject and thus QMS implementation only by one researcher can harden the process.In addition, this volume of screened records highly increases the risk of bias and makes the exclusion process difficult at final stages.Further, database availability is limited by organization affiliation or imposes high costs.Therefore, the author was convinced to withdraw the number of unavailable records which were categorized into both types of resources at the first stages.Furthermore, establishing such inclusion criteria as English records demarcated the searching process, which resulted in missing the findings presented by the studies in other languages such as French, Spanish, Japanese, Korean, Chinese, Portuguese, and so forth.Concerning the limitations, the similarity of sub-dimensions and multifunctionality partially contributes to the creation of some confusion in order to make a decision on their classification into sub-themes and dimensions.
A limited number of previous studies failed to review the aspects of TOD systematically.Such studies normally reviewed a major aspect based on the experience of some pioneer communities such as the United States, Asian (Japanese), and European cities and then developed a basis for the future direction (e.g., Jacobson & Forsyth, 2008;Hess & Lombardi, 2014;Bertolini, Curtis, & Rene, 2012;Dunphy & Porter, 2006;Lierop, Maat, & El-Geneidy, 2016).The other conference proceedings initially measured the potential of a city/region to be a transit-oriented community through reviewing TOD dimensions, success criteria, and the challenges (e.g., Hale & Charles, 2007;Bajracharya, Khan, & Longland, 2005;Black, Tara, & Pakzad, 2016).Several quantitative reviews are available in TOD studies (e.g., Xu, Guthrie, Fan, & Li, 2017).Based on its aim, the present study sought to attain the list of planning and design dimensions by a systematic review of a set of qualitative studies.However, the current study, compared to the previous studies, conducted the review regardless of the context and attempted to benefit from the global experiences.Although previous studies considerably reviewed success factors, the present study emphasized the general measures of the QMS and could achieve the prerequisites.
As underscored earlier, transit-oriented proposals are considerably context-specific in relation to local circumstances since it is exaggeratedly emphasized that TOD is not considered as a "one-sizefits-all" solution.Therefore, new upcoming communities intending to transfer TOD strategies are recommended to specialize these dimensions to their local urban status quo as the next step in TOD planning.It can be developed by a set of future supportive case-based studies.Additionally, QMS is found helpful based on the results obtained during this study.Although QMS have not been considerably prevalent in urban studies, especially respecting integrated planning, it can be diversely used to address various urban issues.Future studies focusing on developing communities are then advised to form a QMS regarding the challenges transit-oriented planning and design encounter.

Funding
This research was supported financially by the Iran Ministry of Science, Research and Technology, Department of Scholarship and Student's Affairs Abroad (Grant number: 9500038, the year of 2017).The author also acknowledges the support of research assistance and primary comments from Dr. Francisco José Lamíquiz Daudén and Professor Dr. Mehdi Azizi.
contents as Transport Reviews, Journal of Transport Geography, Transport Policy, Urban Rail transit, The Journal of Transport and Land Use, Land Use Policy, Journal of the Transportation Research Board, Transportation Research Part A, B, and E, Journal of Public Transportation, Journal of Urbanism, and Urban Policy and Research.

Figure 3 .
Figure 3. Flow diagram for retrieval of papers Source: Author

Figure 4 .
Figure 4. Final included studies and their characteristics.Source: Author

Figure 5 .
Figure 5. Four levels of general dimensions for transit-oriented policy, planning and urban design.

Figure
Figure 6.Development-driven model Source: Author Transportation and Development Policy 6 Center for Transit-Oriented Development 7 Victoria Transport Policy Institute 8 National Parking Association 9 US High Speed Rail Association 10 American Planning Association Regional and urban planning, Urban design, Architecture, Public health, Governance and political science, Finance, Energy and Environment, Geography Figure 2. Information resources, databases, and number of records.

systematic review of the dimensions of transit-oriented urban planning and design Territorios en Formación
| 2019 | N15 | AVANCE DE TESIS DOCTORAL