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Volume 38, Issue 2 (2023)
GeoRes 2023, 38(2): 121-132 |
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Received: 2023/02/16 | Accepted: 2023/04/14 | Published: 2023/04/30
Received: 2023/02/16 | Accepted: 2023/04/14 | Published: 2023/04/30
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Alizadeh T, Azimi Amoli J, Motevalli S, Sarver R. Eco-friendly Public Transportation Scenarios of Tehran Metropolitan in 2031 Horizon. GeoRes 2023; 38 (2) :121-132
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1- Department of Geography and Urban Plannin, Faculty of Humanities, Noor Branch, Islamic Azad University, Noor, Iran
2- Department of Geography and Urban Plannin, Faculty of Literature, Science and Research Branch, Humanities and Social Sciences, Islamic Azad University, Tehran, Iran
2- Department of Geography and Urban Plannin, Faculty of Literature, Science and Research Branch, Humanities and Social Sciences, Islamic Azad University, Tehran, Iran
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Introduction
Today, it is no longer possible to ensure the continuity of economic exploitation without considering pollution, waste, and environmental hazards [Smith, 2019]. This issue applies to all human-made systems, including urban transportation systems. Studies on urban transportation systems encompass diverse economic, social, environmental, managerial, and politico-institutional perspectives. The present research specifically focuses on the environmental perspective within urban transportation systems. From an environmental standpoint, the success of transportation systems is evaluated by the extent of their environmental impacts [Li & Preston, 2015; Searle et al., 2014]. Accordingly, the concept of “sustainable transportation” emerges, referring to a system that neither harms the natural and built environment nor compromises the availability of resources for future generations [Paulsson, 2018]. Such a transportation system not only minimizes environmental damage but also plays an active and progressive role in improving and enhancing environmental quality [Smith, 2019].
Among various modes of urban transportation used worldwide, public transportation is considered one of the most environmentally compatible and sustainable [Addanki & Venkataraman, 2017]. An environmentally friendly public transportation system is characterized by efficiency and effectiveness, environmental desirability, improved accessibility, inclusiveness, competitiveness (in relation to other modes of transport), quality, coordination, and stability [Paulsson, 2018]. These characteristics distinguish public transport from other modes. However, numerous studies show that developing and third-world societies have not embraced environmentally compatible public transportation systems [Derrible, 2016; Chang, 2014]. Several factors contribute to this lack of acceptance. Beyond economic and managerial reasons, one of the most critical causes seems to be the absence of foresight among policymakers and decision-makers in these systems [Ceder, 2021]. The lack of a future-oriented vision prevents the establishment of coherent and effective plans to guide public transportation toward environmental sustainability [Acheampong et al., 2021]. Consequently, transformational programs and policies are implemented only sporadically and temporarily.
In recent years, futures studies, as an interdisciplinary field, have provided methods and tools enabling planners to acquire a systemic understanding of the phenomena they manage, thereby enhancing their systems [Milojević & Inayatullah, 2015]. Generally, the functions of futures studies in planning can be described in two areas: anticipating future risks and expanding managerial foresight [Dorsser, 2016]. Scenario planning is the most critical method of futures studies, capable of modeling possible futures envisioned for organizations and social systems [Martelli, 2014]. Scenario planning is essentially an approach to explore possible futures based on present understanding, designed to uncover what might occur in the future [Bala et al., 2017]. Owing to its complexity and effectiveness in identifying uncertainties, this technique serves as a valuable tool for organizations, enabling them to demonstrate greater flexibility and innovation by envisioning diverse future conditions [Amer & Jetter, 2013].
A review of research on sustainable transportation with a foresight perspective reveals noteworthy findings [Ceder, 2020]. These studies, while analyzing the inefficiencies of private vehicles in the future, emphasize the need for urban transportation systems to rely on green public transportation methods. Governments in future cities must move beyond short-term commitments to reducing carbon emissions within annual cycles and instead adopt a life-cycle approach in urban management [Loo & du Verle, 2017]. Moreover, diversifying transport options and strengthening non-transport urban infrastructures are fundamental prerequisites for achieving environmentally compatible urban transportation in future cities. Studies also highlight the emergence of epidemics and pandemics such as COVID-19 as major challenges to the environmental sustainability of public transport [Gutiérrez et al., 2020; Sy et al., 2020]. In Iranian research, Azizian et al. demonstrated that compressed natural gas (CNG) is the most economical, compatible, affordable, clean, and accessible fuel for localization in Tehran’s urban transportation system [Azizyan et al., 2022]. Similarly, “government support for the private sector” and “societal values” were identified as the most significant driving forces in shaping the future of transportation in Hamedan [Ezzati Arasteh pour et al., 2018]. Ebadinia et al. showed that reducing and eliminating old vehicles constitutes the best low-carbon transportation scenario for Mashhad [Ebadinia et al., 2017]. According to Mohammadpour et al., applying progressive charges on private vehicles based on three parameters, vehicle type, vehicle age, and mileage, can reduce private car use and increase the desirability of public transport [Mohammadpour et al., 2016]. Similarly, implementing technology-driven policies is effective in shifting the transportation market share toward clean technologies and reducing pollutant emissions in Tehran [Manzoor & Safakish, 2011].
Based on the above discussions, this study focuses on future scenarios of Tehran’s public transportation system with an environmental approach. Currently, issues related to public transportation are among the most pressing problems in Tehran and are directly linked to many of the city’s challenges. Tehran is overwhelmingly dominated by private vehicles, and both air pollution and traffic congestion are directly influenced by this reality [Mohammadpour et al., 2016; Manzoor & Safakish, 2011]. For instance, of the 19 million intra-city trips recorded in 2017, 70% were made by private cars and taxis, while only 10% relied on public transportation [Talkhabi et al., 2019; Tehran Municipality, 2018]. Additionally, Tehran’s public transport fleet is outdated. According to available statistics, the average age of buses in Tehran between 2015 and 2018 was 6.5, 6.4, 7, and 7.3 years for the public sector fleet, and 8.4, 9.5, 9.9, and 10.9 years for the private sector fleet, respectively [Tehran Municipality, 2018]. These figures reveal that, due to a lack of investment and fleet renewal, Tehran’s public transportation system is becoming increasingly obsolete, thereby exerting greater negative environmental impacts on the city.
Since Tehran’s public transportation system, as the connecting link to the city’s problems, has received limited attention, and more importantly, because a future-oriented perspective has been largely absent from planning processes, the present study aims to evaluate the future of Tehran’s public transportation system in terms of environmental compatibility by 2031.
Methodology
This study employed a qualitative-quantitative survey approach using a normative scenario modeling framework [Lempert, 2013; Martelli, 2013] and was conducted in 2021 in the metropolitan city of Tehran. Like many other global metropolises, Tehran has recently developed mid-term (5–10 years) vision documents, with the latest vision document prepared for the 2025 horizon. In the present study, the 2031 horizon was considered.
The participants in this research consisted of 12 experts with qualifications in the fields of “futures studies,” “urban transportation and traffic planning,” “urban environment,” and “regional development planning,” who were purposefully selected.
The study was implemented through one qualitative phase and two quantitative phases as follows:
Phase 1 (Qualitative): After identifying the experts, semi-structured interviews with five open-ended questions were conducted. The questions were as follows:
Phase 2 (Quantitative): In the second phase, to narrow down the drivers to the most important and critical ones, a questionnaire consisting of 41 questions with a 9-point scale was distributed to assess the importance and certainty of each driver. The results were analyzed using the mean comparison method, and drivers exhibiting “very high importance,” “very high certainty,” or “very low certainty” were selected for inclusion in the scenario environment.
Phase 3 (Quantitative): In this phase, for each selected driver, three potential states over the next ten years were considered: desirable, static, and critical. Based on these states, a scenario questionnaire comprising 24 questions was designed. The content validity of the questions was confirmed using the Content Validity Ratio (CVR) by six experts [Weimer, 2006]. The logic of this questionnaire was as follows: if any of the desirable, static, or critical states occurred for each driver, what would be the status of the other drivers? The desirable state indicates that the driver will move toward improvement and sustainability over the next ten years. The static state suggests little to no change in the driver’s indicators, and the critical state signifies that the driver will deteriorate. Responses were recorded on a numeric scale from -3 to +3, where +3 indicated the maximum increase and -3 indicated the maximum decrease. The results were analyzed using Scenario Wizard 4.31.
After designing the states and creating a 24×24 cross-impact matrix, experts were asked to evaluate how the occurrence of each of the 24 states over the next ten years in Tehran would affect the occurrence or non-occurrence of other states. By averaging the participants’ responses for each potential state, 492 scenarios were generated. Weak scenarios were excluded from further analysis. To examine the scenario contexts, the relationships between drivers and each scenario, and the interactions of various factors within each scenario’s narrative, a scenario logic or scenario visualization process was conducted.
Findings
The main and subcategories emerging from the interviews collectively revealed 41 drivers related to the public transportation system in Tehran. Among these 41 drivers, 8 key drivers were identified, each with an importance score greater than 7 and a certainty score either greater than 7 or less than 5.
Based on expert responses to potential states derived from the Scenario Wizard software, 492 possible scenarios were generated for Tehran’s public transportation system by the 2031 horizon. Among these scenarios, 11 were classified as strong scenarios, with results indicating a predominance of undesirable states over desirable ones.
Out of a total of 88 states governing the scenario matrix, 28 states (31.81%) were critical, 39 states (44.31%) were static, and 21 states (23.86%) were desirable. Except for the first scenario, which was ideal, scenarios 8, 4, and 7 were identified as the desirable scenarios. Regarding the likelihood of occurrence, scenarios 1 and 11 were considered less credible due to being excessively optimistic or pessimistic. Scenarios 5, 6, and 7 were also deemed invalid due to internal inconsistencies. Conversely, scenarios 2, 3, and 4 had the highest probability of occurrence, while scenario 8 was more ideal than these three but had a low probability of occurrence unless accompanied by appropriate planning. Scenarios 9 and 10 had a moderate probability of occurrence.
For visualization purposes, scenarios were grouped into three main categories based on similarity and proximity:
Scenario 1: This scenario represents an advanced and environmentally compatible public transportation system. Although achieving this scenario within the next ten years seems nearly impossible given the current situation, it offers valuable insights for planners. The scenario illustrates continuous dynamism and progress toward sustainability, characteristic of transportation systems in many developed countries. Beyond the development of quantitative indicators, the scenario emphasizes the system’s resilience and capacity to recover from crises. Consequently, despite its low likelihood, urban transportation and traffic planners in Tehran should incorporate the “sustainability” features of this scenario into other planning scenarios.
Visualization of Static Scenarios: Slow Change and Maintenance of the Status Quo
Scenarios 3 and 4: These two scenarios were highly similar, differing mainly in the higher pollution levels in Scenario 3 compared to Scenario 4; therefore, they are analyzed together. In both scenarios, budget allocations for public transportation are insufficient, resulting in stagnation of other drivers. Without adequate funding, infrastructure modernization is unattainable, and the public transportation fleet continues to deteriorate. Since financial and budgetary issues are fundamental to the development of public transportation systems, one of the main prerequisites for sustainable public transport is absent in these scenarios. The only advantage is the development of new transportation technologies, which may gradually improve other drivers. For instance, travel demand management shows weak but steady improvement; the impact of international sanctions is partially mitigated by importing new technologies from countries like China and Russia; and environmental standards improve to some extent due to updated technology. Moreover, these technologies help reduce pollutants in Scenario 4, whereas pollution remains high in Scenario 3.
Scenarios 6 and 7: Scenario 6 exhibits internal inconsistency because the underlying assumptions conflict. For example, high funding allocation and the development of environmental technologies should positively affect other parameters. However, pollution remains critical, and despite technological advancements, standards do not contribute to public transport sustainability. Additionally, the absence of policy foresight and economic sanctions reduces the quality of equipment and infrastructure. Scenario 7 is similar to Scenario 6, showing inconsistencies between budget allocation and its intended outcomes, such as emission reduction. Both scenarios are considered “floating” and could easily become critical with minor changes in key parameters. These scenarios represent the worst cases among the static scenarios. Although their occurrence in Tehran is plausible, due to their internal inconsistencies, they are not reliable for planning; instead, Scenarios 3, 4, 8, and 10 can serve as a basis for planning.
Scenarios 8 and 10: Scenario 8 is the most favorable among the static scenarios and could occur in Tehran with precise and well-planned interventions. Achieving this scenario requires high budget allocation and development of new environmental technologies in public transport. Additionally, all interfering parameters must be controlled, and at least gradual, continuous improvements should be achieved in six other key drivers. These actions are only feasible under a coherent and goal-oriented vision, which is currently absent, rendering Scenario 8 unreliable. Scenario 10, due to the lack of foresight, is heavily affected by sanctions, which hinders environmental standards and adoption of new technologies. Budget injections in this scenario would primarily support travel demand management and attract private car users to public transport, but insufficient infrastructure would limit success, making this scenario costly and resource-intensive for Tehran’s urban management.
Visualization of Critical Scenarios: Inefficient and Declining System
Scenarios 2 and 5: These scenarios are critical, sharing five states. In both, travel demand management does not improve, and reliance on private cars increases. Due to stagnating environmental standards, severe sanctions affecting fleet and equipment modernization, and dominance of private vehicles, pollution reaches its maximum levels. However, key differences exist: Scenario 5 is inconsistent because high budget allocation and technology development conflict with stagnant environmental standards and weak demand management, rendering it invalid. Scenario 2, however, is a reliable alternative to Scenario 5 and highly probable in Tehran, making it suitable for planning.
After multiple comparisons of the eleven scenarios and further expert consultation, Scenario 2 emerged as the most probable future for Tehran’s urban transport over the next ten years. The internal relationships among its parameters showed stronger correlations than other scenarios, reflecting the current state of Tehran’s public transportation. Features of this scenario—including paralyzing sanctions, lack of managerial foresight, weak travel demand management, insufficient public transport funding, high private car usage, severe pollution, and inability to implement environmental standards—largely match the present situation. Therefore, Scenario 2 is considered the most “static” among all eleven scenarios, representing stagnation and continuation of current conditions over the next decade.
Scenario 9: In this scenario, all parameters except budget are either static or critical. Its only strength is significant budget allocation for public transport, which, without a targeted vision, is unlikely to be effectively utilized. Like Scenario 10, budget funds would primarily maintain and control other system elements. This scenario is heavily affected by sanctions, reducing cooperation with technology- and equipment-producing countries, and is thus “anti-technology.” Despite adequate budget, low environmental technology and sanctions-driven infrastructure deterioration prevent successful demand management and reduction in private car use.
Scenario 11: Scenario 11 represents an entirely critical scenario, continuing and intensifying the current highly unstable situation. The system, without improvements in key indicators, progresses toward deterioration and collapse. Recovery would require a long period, and although such a scenario is plausible in Tehran, relative stability in transport infrastructure and assumptions such as political stability, absence of war, and no economic collapse render this overly pessimistic scenario unreliable.
Discussion
The results of this study can be discussed within the framework of the two main objectives: (1) forecasting the state of Tehran’s public transportation system in terms of environmental sustainability by 2031, and (2) exploring strategies to establish an environmentally compatible public transportation system in Tehran.
Regarding the first objective, the findings indicated that Tehran’s public transport system lacks sustainability indicators such as efficiency, effectiveness, environmental compatibility, and diversity, with its only relative advantage being affordability for low-income populations. These results are consistent with previous studies conducted in Tehran [Manzoor & Safakish, 2011; Mohammadpour et al., 2016; Talkhabi et al., 2019]. Additionally, the results demonstrated that public transportation in Tehran is losing its share of daily trips to private vehicles. According to Tehran Municipality statistics, since 2013, approximately 150 million trips per year have shifted from public transport to private vehicles [Tehran Municipality, 2018]. This finding is supported by other studies [Habibian & Kermanshah, 2016; Javadian & Ferasat, 2017; Alaedini & Fayezi, 2012]. Notably, this trend is not unique to Tehran or Iran but represents a global challenge. For instance, Manoj and Verma reported a projected 14% reduction in public transport share in favor of private cars by 2030 [Manoj & Verma, 2013]. Furthermore, the scenarios developed for 2031 predominantly depict static or critical states, indicating that, at best, the future of Tehran’s public transportation system will resemble the current situation or improve only marginally, far from being environmentally sustainable.
Regarding the second objective, how to establish an environmentally compatible public transportation system in Tehran, two main strategies and one combined strategy were proposed based on identified scenarios and key drivers. The first strategy focuses on technology, including innovations in environmental-friendly public transport technologies, such as fuel type conversion, Intelligent Transportation Systems (ITS), and the use of clean energy. The second strategy emphasizes infrastructure development and fleet modernization, directly tied to public transportation budget allocations. Additionally, combined strategies could be implemented conditionally, contingent on proper policy-making, such as modifying user behavior, managing travel demand, and attracting private vehicle users to public transportation through various taxation mechanisms and traffic restrictions.
Previous studies have addressed aspects of these strategies. For instance, Ceder demonstrated that managerial vision in achieving green and intelligent transportation significantly contributes to environmental sustainability [Ceder, 2021]. Other research show that applying smart technologies in urban bus networks can increase efficiency by 30–50% and reduce bus delays [Suzianti et al., 2022]. Manzoor and Safakish have reported that introducing clean technologies with lower life-cycle costs captured over 70% of the market share, resulting in gradual reductions in pollution levels in Tehran [Manzoor & Safakish, 2011].
However, implementing innovative technologies and green transportation methods requires prerequisites that must be enforced by Tehran’s transportation managers with foresight. This is especially critical in large metropolitan areas [Aldenius et al., 2022]. Haghighat Naeini et al. note that Tehran’s transportation infrastructure is not ready for environmentally compatible projects [Haghighat Naeini et al., 2022]. The physical structure of neighborhoods, particularly in central Tehran, is severely deteriorated [Azizi Fard et al., 2020; Mansourian et al., 2019], and the street network cannot accommodate high traffic volumes. Moreover, even with these prerequisites met, implementing clean transportation strategies requires substantial budget and funding. Financial crises and shocks have historically threatened public transport systems, highlighting the need for innovative financing mechanisms to sustain infrastructure development [Chang, 2014]. A study in Mashhad demonstrates that environmental sustainability in public transport is achieved through metro network expansion, which demands significant budget allocations [Ajza Shokouhi et al., 2015].
Given the current situation, budget constraints, international sanctions, and the deterioration of over 60% of Tehran’s public transport fleet [Tehran Municipality, 2018], combined strategies appear to be a faster and lower-risk option. These strategies generally restrict private vehicle use and reduce emissions from polluting vehicles. Measures such as park-and-ride facilities, parking pricing, and congestion charges have been proposed to decrease private vehicle travel demand [Hounsell et al., 2015]. Implementing environmental taxes, such as fuel taxes, offers two key advantages: low user costs and high revenue for municipal management [Kaisy & Chaaban, 2013]. Fuel taxes, unlike vehicle taxes, remain stable regardless of vehicle use, whereas public transport fares vary with demand. Therefore, if vehicle taxation does not align with usage, short trips by private car remain cheaper than public transport, a critical consideration for environmental tax policy.
Finally, based on the results, several measures are proposed to align Tehran’s public transport system with environmental sustainability requirements:
Conclusion
Based on current reasonable assumptions, the future of Tehran’s public transportation system is expected to be either critical or, at best, stagnant. Evaluating key drivers within the framework of the eleven scenarios indicates that achieving environmental sustainability in Tehran’s public transport system is contingent upon investment and financing for the development of new technologies and environmental standards. The success of these initiatives also depends on strategic visioning and precise policy-making at the metropolitan level.
Acknowledgments: The authors report no acknowledgments.
Ethical Approval: No ethical issues were reported by the authors.
Conflict of Interest: The authors declare no conflicts of interest.
Author Contributions: Alizadeh T (First Author): Principal Researcher/Introduction Writer/Discussion Writer (50%); Azimi Amoli J (Second Author): Assistant Researcher/Introduction Writer (20%); Motavalli S (Third Author): Assistant researcher/Methodologist (20%); Sarvar R (Fourth Author): Assistant Researcher / Introduction Writer/Statistical Analyst (10%)
Funding: This article is derived from a portion of the first author’s doctoral dissertation entitled “Developing Public Transport Development Scenarios with Emphasis on Environmental Dimensions for the Horizon of 1410: Case Study of Tehran Metropolitan Area”, supervised by the second and third authors and advised by the fourth author, conducted at the Faculty of Humanities, Islamic Azad University, Noor Branch, in 1401 (2022–2023). All research expenses were covered by the authors.
Today, it is no longer possible to ensure the continuity of economic exploitation without considering pollution, waste, and environmental hazards [Smith, 2019]. This issue applies to all human-made systems, including urban transportation systems. Studies on urban transportation systems encompass diverse economic, social, environmental, managerial, and politico-institutional perspectives. The present research specifically focuses on the environmental perspective within urban transportation systems. From an environmental standpoint, the success of transportation systems is evaluated by the extent of their environmental impacts [Li & Preston, 2015; Searle et al., 2014]. Accordingly, the concept of “sustainable transportation” emerges, referring to a system that neither harms the natural and built environment nor compromises the availability of resources for future generations [Paulsson, 2018]. Such a transportation system not only minimizes environmental damage but also plays an active and progressive role in improving and enhancing environmental quality [Smith, 2019].
Among various modes of urban transportation used worldwide, public transportation is considered one of the most environmentally compatible and sustainable [Addanki & Venkataraman, 2017]. An environmentally friendly public transportation system is characterized by efficiency and effectiveness, environmental desirability, improved accessibility, inclusiveness, competitiveness (in relation to other modes of transport), quality, coordination, and stability [Paulsson, 2018]. These characteristics distinguish public transport from other modes. However, numerous studies show that developing and third-world societies have not embraced environmentally compatible public transportation systems [Derrible, 2016; Chang, 2014]. Several factors contribute to this lack of acceptance. Beyond economic and managerial reasons, one of the most critical causes seems to be the absence of foresight among policymakers and decision-makers in these systems [Ceder, 2021]. The lack of a future-oriented vision prevents the establishment of coherent and effective plans to guide public transportation toward environmental sustainability [Acheampong et al., 2021]. Consequently, transformational programs and policies are implemented only sporadically and temporarily.
In recent years, futures studies, as an interdisciplinary field, have provided methods and tools enabling planners to acquire a systemic understanding of the phenomena they manage, thereby enhancing their systems [Milojević & Inayatullah, 2015]. Generally, the functions of futures studies in planning can be described in two areas: anticipating future risks and expanding managerial foresight [Dorsser, 2016]. Scenario planning is the most critical method of futures studies, capable of modeling possible futures envisioned for organizations and social systems [Martelli, 2014]. Scenario planning is essentially an approach to explore possible futures based on present understanding, designed to uncover what might occur in the future [Bala et al., 2017]. Owing to its complexity and effectiveness in identifying uncertainties, this technique serves as a valuable tool for organizations, enabling them to demonstrate greater flexibility and innovation by envisioning diverse future conditions [Amer & Jetter, 2013].
A review of research on sustainable transportation with a foresight perspective reveals noteworthy findings [Ceder, 2020]. These studies, while analyzing the inefficiencies of private vehicles in the future, emphasize the need for urban transportation systems to rely on green public transportation methods. Governments in future cities must move beyond short-term commitments to reducing carbon emissions within annual cycles and instead adopt a life-cycle approach in urban management [Loo & du Verle, 2017]. Moreover, diversifying transport options and strengthening non-transport urban infrastructures are fundamental prerequisites for achieving environmentally compatible urban transportation in future cities. Studies also highlight the emergence of epidemics and pandemics such as COVID-19 as major challenges to the environmental sustainability of public transport [Gutiérrez et al., 2020; Sy et al., 2020]. In Iranian research, Azizian et al. demonstrated that compressed natural gas (CNG) is the most economical, compatible, affordable, clean, and accessible fuel for localization in Tehran’s urban transportation system [Azizyan et al., 2022]. Similarly, “government support for the private sector” and “societal values” were identified as the most significant driving forces in shaping the future of transportation in Hamedan [Ezzati Arasteh pour et al., 2018]. Ebadinia et al. showed that reducing and eliminating old vehicles constitutes the best low-carbon transportation scenario for Mashhad [Ebadinia et al., 2017]. According to Mohammadpour et al., applying progressive charges on private vehicles based on three parameters, vehicle type, vehicle age, and mileage, can reduce private car use and increase the desirability of public transport [Mohammadpour et al., 2016]. Similarly, implementing technology-driven policies is effective in shifting the transportation market share toward clean technologies and reducing pollutant emissions in Tehran [Manzoor & Safakish, 2011].
Based on the above discussions, this study focuses on future scenarios of Tehran’s public transportation system with an environmental approach. Currently, issues related to public transportation are among the most pressing problems in Tehran and are directly linked to many of the city’s challenges. Tehran is overwhelmingly dominated by private vehicles, and both air pollution and traffic congestion are directly influenced by this reality [Mohammadpour et al., 2016; Manzoor & Safakish, 2011]. For instance, of the 19 million intra-city trips recorded in 2017, 70% were made by private cars and taxis, while only 10% relied on public transportation [Talkhabi et al., 2019; Tehran Municipality, 2018]. Additionally, Tehran’s public transport fleet is outdated. According to available statistics, the average age of buses in Tehran between 2015 and 2018 was 6.5, 6.4, 7, and 7.3 years for the public sector fleet, and 8.4, 9.5, 9.9, and 10.9 years for the private sector fleet, respectively [Tehran Municipality, 2018]. These figures reveal that, due to a lack of investment and fleet renewal, Tehran’s public transportation system is becoming increasingly obsolete, thereby exerting greater negative environmental impacts on the city.
Since Tehran’s public transportation system, as the connecting link to the city’s problems, has received limited attention, and more importantly, because a future-oriented perspective has been largely absent from planning processes, the present study aims to evaluate the future of Tehran’s public transportation system in terms of environmental compatibility by 2031.
Methodology
This study employed a qualitative-quantitative survey approach using a normative scenario modeling framework [Lempert, 2013; Martelli, 2013] and was conducted in 2021 in the metropolitan city of Tehran. Like many other global metropolises, Tehran has recently developed mid-term (5–10 years) vision documents, with the latest vision document prepared for the 2025 horizon. In the present study, the 2031 horizon was considered.
The participants in this research consisted of 12 experts with qualifications in the fields of “futures studies,” “urban transportation and traffic planning,” “urban environment,” and “regional development planning,” who were purposefully selected.
The study was implemented through one qualitative phase and two quantitative phases as follows:
Phase 1 (Qualitative): After identifying the experts, semi-structured interviews with five open-ended questions were conducted. The questions were as follows:
- As you are aware, there is a significant discourse on sustainable transportation systems among experts, managers, and policymakers both globally and nationally. However, despite increasing discussions on transportation “sustainability,” tangible outcomes remain limited, and in a metropolis like Tehran, despite notable urban management efforts in recent years, the city’s transportation system still lacks sustainability. Therefore, as the first question, what do you consider to be the current challenges and issues regarding the sustainability of Tehran’s urban transportation system? Please also refer to challenges in the national transportation systems.
- Among the various dimensions of transportation sustainability including economic, social, environmental, and infrastructural, which do you consider the most influential on the future of Tehran’s urban transportation system (both positively and negatively)?
- How do you assess the role of government, planning authorities, and municipal management institutions in addressing current and future challenges of Tehran’s transportation system?
- Have any ideas for sustainable transportation options been proposed in Tehran that could be implemented as part of the city’s sustainable transportation system within the next ten years?
- How do you envision the future of Tehran’s urban transportation system in 2031, and what outlook do you anticipate for this system?
Phase 2 (Quantitative): In the second phase, to narrow down the drivers to the most important and critical ones, a questionnaire consisting of 41 questions with a 9-point scale was distributed to assess the importance and certainty of each driver. The results were analyzed using the mean comparison method, and drivers exhibiting “very high importance,” “very high certainty,” or “very low certainty” were selected for inclusion in the scenario environment.
Phase 3 (Quantitative): In this phase, for each selected driver, three potential states over the next ten years were considered: desirable, static, and critical. Based on these states, a scenario questionnaire comprising 24 questions was designed. The content validity of the questions was confirmed using the Content Validity Ratio (CVR) by six experts [Weimer, 2006]. The logic of this questionnaire was as follows: if any of the desirable, static, or critical states occurred for each driver, what would be the status of the other drivers? The desirable state indicates that the driver will move toward improvement and sustainability over the next ten years. The static state suggests little to no change in the driver’s indicators, and the critical state signifies that the driver will deteriorate. Responses were recorded on a numeric scale from -3 to +3, where +3 indicated the maximum increase and -3 indicated the maximum decrease. The results were analyzed using Scenario Wizard 4.31.
After designing the states and creating a 24×24 cross-impact matrix, experts were asked to evaluate how the occurrence of each of the 24 states over the next ten years in Tehran would affect the occurrence or non-occurrence of other states. By averaging the participants’ responses for each potential state, 492 scenarios were generated. Weak scenarios were excluded from further analysis. To examine the scenario contexts, the relationships between drivers and each scenario, and the interactions of various factors within each scenario’s narrative, a scenario logic or scenario visualization process was conducted.
Findings
The main and subcategories emerging from the interviews collectively revealed 41 drivers related to the public transportation system in Tehran. Among these 41 drivers, 8 key drivers were identified, each with an importance score greater than 7 and a certainty score either greater than 7 or less than 5.
Based on expert responses to potential states derived from the Scenario Wizard software, 492 possible scenarios were generated for Tehran’s public transportation system by the 2031 horizon. Among these scenarios, 11 were classified as strong scenarios, with results indicating a predominance of undesirable states over desirable ones.
Out of a total of 88 states governing the scenario matrix, 28 states (31.81%) were critical, 39 states (44.31%) were static, and 21 states (23.86%) were desirable. Except for the first scenario, which was ideal, scenarios 8, 4, and 7 were identified as the desirable scenarios. Regarding the likelihood of occurrence, scenarios 1 and 11 were considered less credible due to being excessively optimistic or pessimistic. Scenarios 5, 6, and 7 were also deemed invalid due to internal inconsistencies. Conversely, scenarios 2, 3, and 4 had the highest probability of occurrence, while scenario 8 was more ideal than these three but had a low probability of occurrence unless accompanied by appropriate planning. Scenarios 9 and 10 had a moderate probability of occurrence.
For visualization purposes, scenarios were grouped into three main categories based on similarity and proximity:
- Desirable scenario (Scenario 1)
- Static scenarios (Scenarios 3, 4, 6, 7, 8, 10)
- Critical scenarios (Scenarios 2, 5, 9, 11)
Scenario 1: This scenario represents an advanced and environmentally compatible public transportation system. Although achieving this scenario within the next ten years seems nearly impossible given the current situation, it offers valuable insights for planners. The scenario illustrates continuous dynamism and progress toward sustainability, characteristic of transportation systems in many developed countries. Beyond the development of quantitative indicators, the scenario emphasizes the system’s resilience and capacity to recover from crises. Consequently, despite its low likelihood, urban transportation and traffic planners in Tehran should incorporate the “sustainability” features of this scenario into other planning scenarios.
Visualization of Static Scenarios: Slow Change and Maintenance of the Status Quo
Scenarios 3 and 4: These two scenarios were highly similar, differing mainly in the higher pollution levels in Scenario 3 compared to Scenario 4; therefore, they are analyzed together. In both scenarios, budget allocations for public transportation are insufficient, resulting in stagnation of other drivers. Without adequate funding, infrastructure modernization is unattainable, and the public transportation fleet continues to deteriorate. Since financial and budgetary issues are fundamental to the development of public transportation systems, one of the main prerequisites for sustainable public transport is absent in these scenarios. The only advantage is the development of new transportation technologies, which may gradually improve other drivers. For instance, travel demand management shows weak but steady improvement; the impact of international sanctions is partially mitigated by importing new technologies from countries like China and Russia; and environmental standards improve to some extent due to updated technology. Moreover, these technologies help reduce pollutants in Scenario 4, whereas pollution remains high in Scenario 3.
Scenarios 6 and 7: Scenario 6 exhibits internal inconsistency because the underlying assumptions conflict. For example, high funding allocation and the development of environmental technologies should positively affect other parameters. However, pollution remains critical, and despite technological advancements, standards do not contribute to public transport sustainability. Additionally, the absence of policy foresight and economic sanctions reduces the quality of equipment and infrastructure. Scenario 7 is similar to Scenario 6, showing inconsistencies between budget allocation and its intended outcomes, such as emission reduction. Both scenarios are considered “floating” and could easily become critical with minor changes in key parameters. These scenarios represent the worst cases among the static scenarios. Although their occurrence in Tehran is plausible, due to their internal inconsistencies, they are not reliable for planning; instead, Scenarios 3, 4, 8, and 10 can serve as a basis for planning.
Scenarios 8 and 10: Scenario 8 is the most favorable among the static scenarios and could occur in Tehran with precise and well-planned interventions. Achieving this scenario requires high budget allocation and development of new environmental technologies in public transport. Additionally, all interfering parameters must be controlled, and at least gradual, continuous improvements should be achieved in six other key drivers. These actions are only feasible under a coherent and goal-oriented vision, which is currently absent, rendering Scenario 8 unreliable. Scenario 10, due to the lack of foresight, is heavily affected by sanctions, which hinders environmental standards and adoption of new technologies. Budget injections in this scenario would primarily support travel demand management and attract private car users to public transport, but insufficient infrastructure would limit success, making this scenario costly and resource-intensive for Tehran’s urban management.
Visualization of Critical Scenarios: Inefficient and Declining System
Scenarios 2 and 5: These scenarios are critical, sharing five states. In both, travel demand management does not improve, and reliance on private cars increases. Due to stagnating environmental standards, severe sanctions affecting fleet and equipment modernization, and dominance of private vehicles, pollution reaches its maximum levels. However, key differences exist: Scenario 5 is inconsistent because high budget allocation and technology development conflict with stagnant environmental standards and weak demand management, rendering it invalid. Scenario 2, however, is a reliable alternative to Scenario 5 and highly probable in Tehran, making it suitable for planning.
After multiple comparisons of the eleven scenarios and further expert consultation, Scenario 2 emerged as the most probable future for Tehran’s urban transport over the next ten years. The internal relationships among its parameters showed stronger correlations than other scenarios, reflecting the current state of Tehran’s public transportation. Features of this scenario—including paralyzing sanctions, lack of managerial foresight, weak travel demand management, insufficient public transport funding, high private car usage, severe pollution, and inability to implement environmental standards—largely match the present situation. Therefore, Scenario 2 is considered the most “static” among all eleven scenarios, representing stagnation and continuation of current conditions over the next decade.
Scenario 9: In this scenario, all parameters except budget are either static or critical. Its only strength is significant budget allocation for public transport, which, without a targeted vision, is unlikely to be effectively utilized. Like Scenario 10, budget funds would primarily maintain and control other system elements. This scenario is heavily affected by sanctions, reducing cooperation with technology- and equipment-producing countries, and is thus “anti-technology.” Despite adequate budget, low environmental technology and sanctions-driven infrastructure deterioration prevent successful demand management and reduction in private car use.
Scenario 11: Scenario 11 represents an entirely critical scenario, continuing and intensifying the current highly unstable situation. The system, without improvements in key indicators, progresses toward deterioration and collapse. Recovery would require a long period, and although such a scenario is plausible in Tehran, relative stability in transport infrastructure and assumptions such as political stability, absence of war, and no economic collapse render this overly pessimistic scenario unreliable.
Discussion
The results of this study can be discussed within the framework of the two main objectives: (1) forecasting the state of Tehran’s public transportation system in terms of environmental sustainability by 2031, and (2) exploring strategies to establish an environmentally compatible public transportation system in Tehran.
Regarding the first objective, the findings indicated that Tehran’s public transport system lacks sustainability indicators such as efficiency, effectiveness, environmental compatibility, and diversity, with its only relative advantage being affordability for low-income populations. These results are consistent with previous studies conducted in Tehran [Manzoor & Safakish, 2011; Mohammadpour et al., 2016; Talkhabi et al., 2019]. Additionally, the results demonstrated that public transportation in Tehran is losing its share of daily trips to private vehicles. According to Tehran Municipality statistics, since 2013, approximately 150 million trips per year have shifted from public transport to private vehicles [Tehran Municipality, 2018]. This finding is supported by other studies [Habibian & Kermanshah, 2016; Javadian & Ferasat, 2017; Alaedini & Fayezi, 2012]. Notably, this trend is not unique to Tehran or Iran but represents a global challenge. For instance, Manoj and Verma reported a projected 14% reduction in public transport share in favor of private cars by 2030 [Manoj & Verma, 2013]. Furthermore, the scenarios developed for 2031 predominantly depict static or critical states, indicating that, at best, the future of Tehran’s public transportation system will resemble the current situation or improve only marginally, far from being environmentally sustainable.
Regarding the second objective, how to establish an environmentally compatible public transportation system in Tehran, two main strategies and one combined strategy were proposed based on identified scenarios and key drivers. The first strategy focuses on technology, including innovations in environmental-friendly public transport technologies, such as fuel type conversion, Intelligent Transportation Systems (ITS), and the use of clean energy. The second strategy emphasizes infrastructure development and fleet modernization, directly tied to public transportation budget allocations. Additionally, combined strategies could be implemented conditionally, contingent on proper policy-making, such as modifying user behavior, managing travel demand, and attracting private vehicle users to public transportation through various taxation mechanisms and traffic restrictions.
Previous studies have addressed aspects of these strategies. For instance, Ceder demonstrated that managerial vision in achieving green and intelligent transportation significantly contributes to environmental sustainability [Ceder, 2021]. Other research show that applying smart technologies in urban bus networks can increase efficiency by 30–50% and reduce bus delays [Suzianti et al., 2022]. Manzoor and Safakish have reported that introducing clean technologies with lower life-cycle costs captured over 70% of the market share, resulting in gradual reductions in pollution levels in Tehran [Manzoor & Safakish, 2011].
However, implementing innovative technologies and green transportation methods requires prerequisites that must be enforced by Tehran’s transportation managers with foresight. This is especially critical in large metropolitan areas [Aldenius et al., 2022]. Haghighat Naeini et al. note that Tehran’s transportation infrastructure is not ready for environmentally compatible projects [Haghighat Naeini et al., 2022]. The physical structure of neighborhoods, particularly in central Tehran, is severely deteriorated [Azizi Fard et al., 2020; Mansourian et al., 2019], and the street network cannot accommodate high traffic volumes. Moreover, even with these prerequisites met, implementing clean transportation strategies requires substantial budget and funding. Financial crises and shocks have historically threatened public transport systems, highlighting the need for innovative financing mechanisms to sustain infrastructure development [Chang, 2014]. A study in Mashhad demonstrates that environmental sustainability in public transport is achieved through metro network expansion, which demands significant budget allocations [Ajza Shokouhi et al., 2015].
Given the current situation, budget constraints, international sanctions, and the deterioration of over 60% of Tehran’s public transport fleet [Tehran Municipality, 2018], combined strategies appear to be a faster and lower-risk option. These strategies generally restrict private vehicle use and reduce emissions from polluting vehicles. Measures such as park-and-ride facilities, parking pricing, and congestion charges have been proposed to decrease private vehicle travel demand [Hounsell et al., 2015]. Implementing environmental taxes, such as fuel taxes, offers two key advantages: low user costs and high revenue for municipal management [Kaisy & Chaaban, 2013]. Fuel taxes, unlike vehicle taxes, remain stable regardless of vehicle use, whereas public transport fares vary with demand. Therefore, if vehicle taxation does not align with usage, short trips by private car remain cheaper than public transport, a critical consideration for environmental tax policy.
Finally, based on the results, several measures are proposed to align Tehran’s public transport system with environmental sustainability requirements:
- Exemption from value-added taxes in partnership contracts to encourage foreign investment in green transportation.
- Development of integrated non-motorized or lightweight transport systems on secondary arterial streets, alleys, and minor streets.
- Accounting for environmental costs of transportation in government auditing systems and taking actions to reduce them.
- Reducing fossil fuel subsidies and reallocating the savings for fleet modernization.
- Lowering import tariffs for public transport vehicles to accelerate fleet renewal.
- Gradually switching fuel types over a 10-year period from diesel and gasoline to clean fuels.
- Allocating a portion of municipal taxes and fees for the production of cellulosic biofuels and ethanol.
- Annually replacing 5% of the aged bus fleet with new vehicles.
- Increasing metro and bus fleet capacity by 5% annually and hiring additional staff and drivers.
- Phasing out 5% of government-owned aging vehicles each year.
- Converting 2–5% of city buses to hybrid vehicles annually, subject to budget constraints.
- Repairing and gradually replacing defective train wagons by 2031.
- Implementing a used vehicle import policy to renew the fleet under limited budget conditions (e.g., 5-year-old European vehicles with acceptable emission levels).
Conclusion
Based on current reasonable assumptions, the future of Tehran’s public transportation system is expected to be either critical or, at best, stagnant. Evaluating key drivers within the framework of the eleven scenarios indicates that achieving environmental sustainability in Tehran’s public transport system is contingent upon investment and financing for the development of new technologies and environmental standards. The success of these initiatives also depends on strategic visioning and precise policy-making at the metropolitan level.
Acknowledgments: The authors report no acknowledgments.
Ethical Approval: No ethical issues were reported by the authors.
Conflict of Interest: The authors declare no conflicts of interest.
Author Contributions: Alizadeh T (First Author): Principal Researcher/Introduction Writer/Discussion Writer (50%); Azimi Amoli J (Second Author): Assistant Researcher/Introduction Writer (20%); Motavalli S (Third Author): Assistant researcher/Methodologist (20%); Sarvar R (Fourth Author): Assistant Researcher / Introduction Writer/Statistical Analyst (10%)
Funding: This article is derived from a portion of the first author’s doctoral dissertation entitled “Developing Public Transport Development Scenarios with Emphasis on Environmental Dimensions for the Horizon of 1410: Case Study of Tehran Metropolitan Area”, supervised by the second and third authors and advised by the fourth author, conducted at the Faculty of Humanities, Islamic Azad University, Noor Branch, in 1401 (2022–2023). All research expenses were covered by the authors.
Keywords:
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