Document Type : Research Paper
Authors
1
Department of Urban Planning, Iran University of Science and Technology, Tehran, Iran
2
Department of Urban Planning, Iran University of Science and Technology , Tehran, Iran
10.22034/jsc.2026.584807.1915
Abstract
A B S T R A C T
Urban form serves as a pivotal determinant in urban planning and design, playing a critical role in traffic safety performance and pedestrian vulnerability. The present study seeks to provide a spatially grounded urban form design guide aimed at enhancing the safety quality for both vehicles and pedestrians within the Park Mellat neighborhood of Mashhad. applied research adopted a mixed-methods (quantitative-qualitative) design, analyzing 277 recorded traffic accidents occurring between 2018 and 2020. Spatial data were processed using ArcMap, while 53 indicators across five urban design systems were assessed through field observations and a review of higher-order planning documents. Statistical analysis was performed using logistic regression and odds ratios. Content validity was confirmed by 15 experts, and reliability was established through test-retest procedures (85%).Pedestrians accounted for over 50% of accident casualties. In contrast to findings reported in international studies, wide roadways (30–38 m)-which were associated with 76% of accidents—high population density (250–300 persons/ha), and proximity to Park Mellat, where 53% of pedestrian accidents were concentrated, were directly correlated with diminished safety. Additionally, mixed-use land uses and linear retail establishments along the northern and eastern edges, along with a concentration of billboards (70% of the 95 signs), exhibited a significant positive association with accident frequency. Conversely, predominantly residential land use within the interior fabric, narrow streets (12–14 m), and high building density were associated with enhanced safety outcomes. The proposed model incorporates 14 corrective dimensions—including reducing roadway widths, moderating density along the park margins, organizing signage, and establishing continuity in pedestrian spaces—which collectively provide a robust foundation for structural interventions aimed at improving vehicular and pedestrian safety.
Extended Abstract
Introduction
Places are inherently characterized by a multitude of qualities, and human interventions prove successful only when these attributes are thoroughly understood. At its core, urban design is centrally concerned with creating better environments for people. With the proliferation of motorized life and the concomitant rise in mobility demands, streets and roadways have evolved into foundational elements of urban structure. Accordingly, urban design must foreground principles such as ease of movement, accessibility, and safety. The surge in travel demand, however, has imposed substantial social, economic, and environmental costs—including traffic accidents, congestion, energy consumption, and air pollution. The Public Health Agency of Canada (2010) has corroborated the significant association between urban form and public health outcomes, particularly with respect to traffic safety. Notwithstanding the ongoing efforts of architects and urban designers to implement traffic-calming measures, other critical dimensions—including land-use distribution, the siting of open spaces, streetscaping, and the hierarchical organization of road networks—have remained largely overlooked. The present study specifically addresses these under-explored dimensions. Over the past half-century, rising car ownership and mounting traffic congestion have rendered roadway safety a major public health challenge, with young adults aged 15 to 44 bearing the brunt of fatalities. According to the World Health Organization, road traffic injuries rank as the ninth leading cause of death globally. In Iran, where accident rates are notably high, they represent the second leading cause of mortality, following cardiovascular diseases (Azimi & Farouqi, 2008). National statistics for 2013 report 17,997 traffic-related fatalities, of which 28.1% occurred in urban settings (Ministry of Roads and Urban Development, 2013). Within this context, Mashhad ranks 25th among 53 global metropolises, with a fatality rate of 8.5 per 100,000 population. Given that ensuring safety constitutes one of the five overarching principles of roadway design, the primary objective of this study is to formulate a comprehensive urban form design guide for the Park Mellat neighborhood in Mashhad, aimed at improving the quality of safety for both pedestrians and vehicles.
Methodology
The present study is applied in nature and falls within the domain of developmental research, as it draws upon the theoretical foundations established in basic research to address practical human needs and refine the tools, patterns, and methods of urban design aimed at enhancing vehicular and pedestrian safety. Given the nature of the data, this research adopts a mixed-methods approach (combining quantitative and qualitative techniques). The integration of these two approaches concurrently ensures both validity and reliability while facilitating a more comprehensive understanding of the research problem. The statistical population of this study comprises all recorded intra-urban traffic accidents in Mashhad over three statistical periods—2018, 2019, and 2020—totaling 277 incidents. The primary data consist of various urban form layers derived from the spatial database (Geographic Information System), the Comprehensive and Detailed Plans of Mashhad, and accident statistics obtained from the Traffic Organization of Mashhad Municipality. Additionally, part of the data was gathered through field surveys, the findings of a traffic safety expert's roadway audit, and systematic observations aimed at documenting the behavioral patterns of residents and employees within the study area.
The content validity of the indicators was confirmed by 15 experts in urban planning, urban design, and transportation (comprising 8 university professors and 7 senior traffic specialists). To this end, the Content Validity Ratio (CVR) method was employed, and indicators receiving a CVR score below 0.49 were excluded from the analysis (Lawshe, 1975). The reliability of the field data was established through a test-retest procedure conducted at a two-week interval, yielding a correlation coefficient of 85%. Data collection was carried out through both documentary and field methods. For the documentary approach, the theoretical underpinnings of the research and quantitative data were compiled by consulting books, journal articles, transportation statistical yearbooks, maps, approved urban plans, dissertations, and online databases. In the field survey, qualitative data were gathered through direct and participatory observation by the researcher, in-depth interviews with local residents, and photographic documentation. Initially, accident records and relevant information were classified using Microsoft Excel. Following quality control and data screening procedures, statistical analyses were performed using SPSS version 26.
Results and Discussion
The findings of the present study reveal that the relationship between urban form and traffic safety in the Park Mellat neighborhood diverges substantially, in several respects, from the established paradigms derived from prior studies (predominantly conducted in developed countries). This discrepancy underscores the imperative for locally contextualized urban design models.
1. Challenging Global Patterns in the Local Context: Contrary to studies emphasizing the role of fine-grained, compact blocks in reducing vehicle speeds and improving safety (Marshall & Garrick, 2011), in the Park Mellat neighborhood, fine-grained and medium-sized blocks located along arterial roads were associated with increased accident frequencies. Furthermore, unlike findings that link high population density with enhanced pedestrian safety (Jones & Jha, 2010), the high-density area along the eastern edge (adjacent to Park Mellat) accounted for 44% of total recorded accidents. This contradiction suggests that density alone is not a determinant of safety; rather, it is "density combined with an appropriately designed street network and the segregation of vehicular and pedestrian flows" that plays the decisive role.
2. The Paradox of Public Spaces: A finding consistent with both domestic (Ayati & Bahraini, 2016) and international research confirms the role of trip-attracting land uses. However, the novel insight offered by this study lies in the observation that the presence of a high-quality public space (Park Mellat) adjacent to wide, high-speed thoroughfares (Emamat and Moallem Boulevards) not only failed to enhance safety but actually emerged as the primary hotspot for pedestrian accidents. This finding aligns with the OECD (1998) warning that the mere provision of pedestrian facilities does not guarantee increased safety, while extending that caution to a broader scale concerning the relationship between "trip-attracting uses" and "high-speed roadway networks."
3. The Moderating Role of Physical Form: Another noteworthy finding concerns the inverse effect of certain indicators. While the literature generally suggests that wide roadways and low building density are associated with higher speeds and diminished safety (Norouzi et al., 2014), in the Park Mellat neighborhood, narrow internal streets (12–14 m) and high building density (compact fabric) were correlated with enhanced safety. This outcome can be attributed to the "physical enclosure effect," which fosters a sense of natural surveillance and reduces drivers' perceived speed, thereby rendering the environment safer for pedestrians.
4. Non-significant Indicators and Contextual Complexity: A considerable number of indicators (e.g., MA5, MA7, MA9, ULS1, ULS6) exhibited no significant association with safety in this neighborhood. This finding is entirely consistent with the argument advanced by Ewing and Cervero (2018) that the cumulative effect of design qualities surpasses the sum of individual attributes. In other words, the presence of improved sidewalks (MA11) or bicycle lanes (MA12) alone is insufficient to enhance safety within a context where the street network lacks a logical hierarchy and is intermixed with trip-generating activities.
Overall, the preceding discussion demonstrates that localized, piecemeal physical interventions (such as traffic calming) cannot yield sustainable safety improvements unless accompanied by a fundamental reassessment of the macro-scale urban form—encompassing street hierarchy, land-use distribution, and the siting of public spaces.
Conclusion
The most significant finding of this study is that the spatial clustering of accidents is a function of the dissonant juxtaposition of three key components: (1) wide roadways with a fragmented hierarchy; (2) high-traffic public spaces with direct access to these roadways; and (3) the skewed distribution of trip-attracting activities and billboards along these axes. Contrary to common assumptions, factors such as high population density and fine-grained blocks, within this specific context, did not prove to be safety-enhancing; rather, owing to their adjacency to the primary roadway network, they acted as aggravating factors.
Furthermore, despite their considerable theoretical potential, urban landscape systems and public spaces have failed to play an effective role in improving safety under existing conditions. A major public space such as Park Mellat, in the absence of secure buffer zones and continuous pedestrian access routes, has effectively become a traffic trap for pedestrians. Moreover, the lack of a significant correlation between many conventional indicators—including lighting, paving quality, and roadside greenery—and the accident pattern underscores the reality that such features lose their effectiveness when the overarching structure of the roadway network remains inherently unsafe.
In addressing the core research question, the urban form design guide developed here—organized around 14 principal axes—does not constitute a one-size-fits-all prescription but rather a spatially explicit, evidence-based decision-making framework that delineates intervention priorities. This guide emphasizes reducing the geometric dimensions and lengths of major arteries, moderating population densities around public spaces, relocating trip-generating land uses, and establishing a safe access hierarchy for pedestrians.
In conclusion, this study demonstrates that achieving a "city for all" necessitates moving beyond a doctrinaire application of global findings and embracing the principle that a safe urban form is one in which the roadway network, land-use distribution, and the siting of public spaces are integrated and calibrated to serve the most vulnerable users—pedestrians. The model proposed herein can serve as a template for revising urban development plans and prioritizing safety interventions in other contexts across Mashhad and other Iranian metropolises.
Funding
There is no funding support.
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved the content of the manuscript and agreed on all aspects of the work declaration of competing interest none.
Conflict of Interest
Authors declared no conflict of interest.
Acknowledgments
We are grateful to all the scientific consultants of this paper.
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