An Investigation of Transportation Availability for Socially Sustainable Dhaka, Bangladesh

In pursuing socially sustainable urban conditions, social sustainability has assumed a prominent position on the global stage. Notably, transportation availability emerges as a pivotal facet within the domain of social sustainability [1]. The accessibility of fundamental amenities such as transportation plays an instrumental role in cultivating an affordable living environment [2, 3]. Sustainable urban transportation planning not only enhances the quality of life but also fosters liveable cities [4]. Similarly, the availability of transport increases connectivity which increases the accessibility of local services [5]. Furthermore, the provision of sound transportation facilities within communities has been shown to ameliorate the overall living conditions of residents [6]. Considering these observations, it becomes increasingly apparent that the significance of transportation availability has engendered a heightened imperative for the creation of a sustainable future. Nonetheless, it is crucial to acknowledge that developing countries encounter substantial challenges in ensuring equitable transportation access for their citizens.

Dhaka, located within a developing country, is an example of the remarkable urban growth witnessed in recent decades. Over four decades, Dhaka has become one of the world's megacities due to rapid urbanization and significant population growth [7]. There is a major struggle in Dhaka's urban community against social issues, with public transportation being a prominent concern due to the city's rapid urbanization [8-10]. It is important to note that urbanization generally contributes to the development of social amenities and services such as transportation [11], but rapid urbanization also affects the provision of transportation facilities. As a result, Dhaka's rapid urbanization affects its ability to provide essential services, such as the availability of transportation, as government revenues for the maintenance and provision of city amenities are minimal [12]. In Dhaka, traffic congestion is the most pressing livability issue, affecting middle and lower-income groups [8]. It is crucial to consider transportation availability as a vital aspect of social sustainability in urban areas, particularly in developing cities. This aspect should not be overlooked to achieve socially sustainable urban spaces.

Likewise, numerous researchers have dedicated their efforts to the study of transportation within urban areas. They highlighted certain issues, such as ‘A bibliometric analysis of sustainable urban transportation [13]’, ‘Linkage between transportation, urbanization, economic growth and GHG emissions in Southeast Asian Nations [14]’, ‘Strengthening green transportation [15]’, ‘Exploration of sustainable urban transportation development [16]’, ‘Sustainable development of urban transportation and ecological environment [17]’, ‘Strategic planning of urban transportation system [18]’, ‘Large urban transportation infrastructure networks [19]’. None of the studies focuses on assessing the current state of transportation availability which is crucial for ensuring social sustainability in developing country cities. Thus, this study effectively addresses the current gap in research by assessing the current state of transport availability in socially sustainable urban areas of Dhaka city. Also, comprehending the intricate interplay between transport availability and socially sustainable urban development assumes paramount significance for all stakeholders vested in the progress and well-being of Dhaka city. As a result, the primary research objectives (RO) in the present study are:

RO1: To investigate the current status of transportation availability as a significant aspect of social sustainability in Dhaka.

RO2: To examine the impact of transportation availability on socially sustainable Dhaka.

The implication of this study lies in its empirical approach, which contributes fresh insights to scholarly work. First, this research endeavors to quantify the present situation of transportation availability as a means to foster social sustainability within the city of Dhaka. While prior studies have extensively examined various issues of transportation, none have comprehensively unveiled the contemporary situations of transportation availability which is very essential for the policy and practice of city planners and authorities. Consequently, this study augments the existing knowledge base by furnishing precise empirical evidence. This empirical evidence is a crucial resource that can greatly benefit governmental bodies, policymakers, urban planners, and implementing agencies. It equips them with the necessary data to develop effective strategies, formulate policies, and execute plans aimed at realizing a socially sustainable Dhaka city. Second, this study elucidates the impact of transportation availability on the trajectory of socially sustainable urban development. The research findings provide valuable insights to city authorities and stakeholders, facilitating informed decision-making activities to enhance the livability and overall quality of life in the city. This study’s findings are needed for cities in developing nations dealing with the same problems arising from rapid urbanization, such as Kolkata, Delhi, Shanghai, Beijing, Mumbai, and others. Third, this study also facilitates achieving target 11.2 under the Sustainable Development Goals (SDG-11) titled “Sustainable Cities and Communities”. Target 11.2 of the UN SDGs aims to ensure safe, affordable, accessible, and sustainable transportation systems for everyone. This includes expanding public transportation to improve road safety, with a focus on meeting the needs of vulnerable communities such as women, children, people with disabilities, and the elderly.

3.1 Study area, sample selection, and data collection

The study unequivocally examined Dhaka city as a prime example of a developing country. This city is placed at 23°42′ to 23°52′ latitude in the north and 90°22′ to 90°32’ longitude in the east [7] with a total coverage area of 302.92 sq. Km [47]. Dhaka's urbanization has rapidly elevated it to megacity status, bringing with it the burdens of extensive population density in recent decades. Also, 63% of Dhaka's population growth was due to migration, while only 37% resulted from natural increase [40]. In 2018, Dhaka ranked 9th among the top 10 cities by urban population and is projected to rank 4th by 2030 [39]. With a population density of 41,000 per square kilometer, Dhaka ranks 1st worldwide in urban area density [48]. For this reason, the researchers chose Dhaka as a case study city which is representative of other urbanizing cities suffering from similar problems.

This study intends to choose a sample from the population of people in Dhaka, specifically focusing on voters who have participated in the survey. Voters can provide insights into Dhaka's social sustainability status due to their prior residency in the area. The study only analyzes voters to maintain a fair sample size, while considering the overall population of Dhaka city. This decision is due to the challenges of gathering information from all voters, considering the constraints of time and resources the researcher faces. Using G*Power 3.1.9.7, we estimated that 164 participants would be an adequate sample size for this investigation, with a true power greater than 0.80 [49]. Accordingly, this investigation required a minimum of 164 participants (see Figure 1).

1.png

Figure 1. Sample size calculation

Table 1. Profile of survey participants

Note: The total respondents are 564.

Participants were selected using a multistage sampling process. In the first phase, the purposive sampling method is mainly used to find the voters of Dhaka city. In the second phase, a systematic selection method was used to select 23 wards from the municipal corporation. During the third phase, we used a systematic sampling method to choose the target respondents, who were the residents of the voters, by gathering voter information from the “Ward Commissioner's Office and the Election Commission of Bangladesh”. At the outset, 590 respondents filled out the survey. However, another nine answers and seventeen responses were excluded from the voter status process validation because they were incomplete. The study's structured questionnaire survey yielded 564 answers from people living in Dhaka city. The details of the demographic profile of the respondents are presented in Table 1.

Furthermore, this study embraced a quantitative research approach, employing a survey technique to gather data from the residents of Dhaka. This approach enabled the researcher to assess the actual availability of transportation for the social sustainability of Dhaka. From May to November 2021, the questionnaires were distributed to gather responses, spanning six months to amass a comprehensive dataset for the study. In addition to primary data collection, this study also relied on secondary sources. The secondary sources included an exhaustive examination of relevant published material, including scholarly publications, documents from international or UN agencies, NGOs, Bangladesh government gazettes, news releases, and official documents.

In the pre-testing phase, this study focused on assessing the content validity of the survey questionnaire. To measure the content validity of "individual items (I-CVI)" and the "overall scale (S-CVI)", a structured questionnaire was administered to six distinguished experts, comprising “Directors of Urban Planning and Development”, “City Planners”, Consultants, and “Program Analysts” from national and international arenas. To assess relevance, the questionnaire utilized a four-point scale, evaluating dimensions such as consistency, conceptual representativeness, relevancy, and clarity (see Table A). As per experts' recommendations, it was determined that four items related to transportation availability are essential for Dhaka city, with only minor suggestions for rephrasing some of the language for better clarity. Based on the relevance ratings and input from experts, these four items were subsequently selected for the pilot study. A sample size of 30 participants from the target population was deemed appropriate for pilot testing [50]. The researchers conducted a pilot study before the main questionnaire survey, but no significant differences were observed between the pilot and final results.

3.2 Variables measurement

This section discusses the measurements of all variables including the responding variable, explanatory variable, and covariates. Some widely used techniques such as PCR and factor analysis are used to measure the concurrent relationship or causality between the variables. However, these techniques are mostly used to reduce the data. Therefore, the objective of this study is to use only the weighted average score method to reveal Dhaka's current status of transportation availability.

3.2.1 Measurement of socially sustainable urban development

The “New Urban Agenda” was the primary focus of the 2016 UN “Conference on Housing and Sustainable Urban Development”. One of the most critical dimensions of this agenda is socially sustainable urban development [51]. The New Urban Agenda intends to accomplish SDG 11 by creating human settlements that are inclusive, safe, resilient, and sustainable. The literature increasingly highlights the importance of social dimensions in sustainable urban development [25-29]. A 5-point Likert scale was used to measure socially sustainable urban development across five items. Table B provides a detailed illustration of the measurement items. Followed by this study measured the weighted average score of five items for each response which was used as a responding or dependent variable.

3.2.2 Measurement of transportation availability

This study used transportation availability to measure social sustainability in Dhaka, as per the “National Urban Sector Policy”. We used survey questionnaires with a 5-point Likert scale and four items were employed to assess the availability of transportation. Respondents were required to provide their responses to the items. All items were embraced by Ali et al. [1]. The reason for adopting the transport availability items is that Bangladesh has no specific indicators to measure it. Details of measuring items of each explanatory variable are presented in Table C.

3.2.3 Measurement of covariates

Ensuring sustainable urban development for society varies based on the citizen’s age. Also, equitable facilities for confirming sustainable urban progress depend on the gender of city dwellers. These issues also remain considerable in the case of socially sustainable urban growth in Dhaka. Moreover, citizens’ age and gender are also vital issues for ensuring transportation availability [1]. Thus, this study controls the citizens' age (count data for each respondent) and gender (categorical data 1 for male and 2 for female).

3.3 Data overview

In Table 2, the descriptive analysis of variables such as socially sustainable urban development (SSUD), transport availability (TA), age, and gender has been reported. A total number of 564 responses are considered. In the case of SSUD, this study found the respondents' opinion lies between 1 to 4, indicating that none of the respondents showed they strongly agree with the current status. Likewise, identical responses were found in the case of TA2 to TA4. However, the maximum value was found 5 (strongly agree) for TA1. This study found a Skewness value less than ±1 which indicates the normality of the responding and explanatory variables. However, the Kurtosis value was found higher than ±2. Although, according to Hair et al. [52] and Byrne [53], data is deemed normal if the Skewness value is between ±2 and Kurtosis is ±7, this study also ran separate normality tests (i.e., joint test, Shapiro-wilk W test) further to investigate the normality status of responding and explanatory variables (see in Table D). Thus, this study can reject the null hypothesis (variable is normally distributed) and conclude that there is sufficient evidence to state that the variable is not normally distributed.

Furthermore, Cronbach's Alpha was used to assess the research instruments' quality and measure the adopted items' reliability where the Alpha value must be higher than 0.70 [54]. According to the reliability analysis conducted in this study, the overall Cronbach's Alpha value was found to be 0.899. The analysis also revealed that the 04 items had significantly higher reliability, as shown in Table 3. Therefore, the measuring variable used in this study meets the required threshold value of Cronbach's Alpha, making it valid, reliable, and acceptable for the study.

According to the correlation matrix shown in Table 4, none of the variables are highly correlated with each other, indicating that there are no considerable multicollinearity issues. Moreover, this study also diagnoses multicollinearity issues, results reported in Table E. Finally, this study concludes that there is no multicollinearity issue in the dataset.

Table 2. Data overview (Descriptive analysis)

Note: SSUD: Socially Sustainable Urban Development, TA1: “Reach to bus stop easily from home”, TA2: “Availability of public transport in Dhaka”, TA3: “Satisfaction level of public transportation”, and “TA4: Public Transport accessibility (i.e., disabled/special need)”.

Table 3. Reliability analysis

Table 4. Correlation matrix

Note: Refer to Table 2 for the elaboration of SSUD, TA1, TA2, TA3, and TA4.

3.4 Model specification

Cross-sectional regression can be used in many aspects, especially, to explore and establish correlations or associations between variables and examine how demographic factors (age, income, education) relate to an outcome variable [55]. Despite, the causality limitation (it identifies correlations but not causal relationships) and weaker evidence of causality compared to longitudinal or experimental designs, this study used cross-section OLS to make causal inferences, particularly to control for confounding variables [56]. Moreover, it helps us to provide valuable insights for policymakers by identifying current correlations or disparities that may require intervention [57]. For example, understanding the current relationship between education and income can help in designing targeted policies [58]. In this context, this study considers cross-sectional ordinary Least Squire (OLS) as a benchmark regression to measure the impact of transportation availability on SSUD. Also, we cross-validated the results of benchmark regression through Poisson regression concerning the Poisson distribution of the dataset.

3.4.1 Benchmark regression

To measure the relationship between the SSUD and the transportation availability of Dhaka, this study considers the cross-section OLS as a benchmark model without any covariates. Hence, the regression equation is:

$Y=\int X, Z$              (1)

where, Y is measured with the weighted average of all individual items of socially sustainable urban development (SSUD). Also, X is the categorical variable consisting of four different questions measured by a 5-point Likert scale, whereas Z represents the covariates namely AGE and GENDER of each respondent ‘n’, ε is the error term. Hence, the actual regression function is:

$\begin{gathered}\operatorname{SSUD}_{W A S}=\alpha+\beta_1 T A_1+\beta_2 T A_2+\beta_3 T A_3+\beta_4 T A_4+z_n+\varepsilon\end{gathered}$                (2)

3.4.2 Poisson regression

The Poisson model posits that the event count in research denoted as Y, conforms to a Poisson distribution with parameter µ: Y Poisson (µ). The logarithm of µ is represented by a linear combination of variables as follows.

$\log (\mu)=C \beta+D$           (3)

Here, C represents a matrix of covariates with dimensions n × (k + 1), where n is the number of observations and k is the number of covariates. X₀, the 1^st column of X, is often composed entirely of 1^st to facilitate the calculation of an intercept. D represents an offset variable, the log of supplement time, or the total count of respondents. The ‘log-likelihood function’ for the ‘Poisson model’ can be written as:

$\begin{gathered}\ell(\beta)=\sum_{i=1}^n\left[-\exp \left(x_i \beta+z_i\right)+\left(x_i \beta+z_i\right) y_i\right. \left.-\log \left(y_{i}!\right)\right]\end{gathered}$

The parameters $\beta_j, j=0, \ldots . k$, are estimated via ‘maximum likelihood (ML)’ by solving the following score equations:

$U_j(\beta)=\sum_{i=1}^n x_{i j}\left[y_i-\exp \left(x_i \beta+z_i\right)\right]=0$

where, $j=0, \ldots, k, x_{i j}$ denotes the observed value of the ‘j-th’ covariate for the ‘i-th’ subject, $x_i$ is the row vector containing covariate values for the ‘i-th’ subject, and $Z_i$ corresponds to the counterbalance value for the subject.

Transportation availability is one of the significant features of social sustainability. The study revealed that the residents of Dhaka city are dissatisfied with the availability of transportation. A case study in Irbid, Jordan found moderate to relatively low satisfaction with transportation availability among respondents [1]. In addition, there was widespread dissatisfaction with Dhaka's existing transport system, with poor use of public transport among Dhaka city residents due to poor sustainability and the city's narrow and congested roads [20]. Additionally, it was observed that the combination of high population density and limited access to public transportation compels residents to rely on non-transit modes of travel, such as auto-rickshaws and taxicabs, despite their comparatively higher costs.

Moreover, the statistical examination conducted in this study unveiled a notable positive correlation between transportation availability and socially sustainable urban development within Dhaka city. The profound impact of urban form on transportation availability is a pivotal indicator of social sustainability in Irbid, Jordan [1]. Transportation availability emerges as a crucial variable closely linked to the advancement of socially sustainable urban growth in the City of Dunedin, New Zealand [3]. The rapid urbanization witnessed in Baghdad, the capital of Iraq, poses a formidable challenge to meet the growing demand for transport availability, which is critical to ensuring sustainable urban development [64].

Smart cities are instrumental in fostering the intellectual growth of urban transportation systems while addressing the imperative of sustainable urban development [65]. Transport holds a pivotal position in the planning for urban sustainability, where cities institute programs and policies geared toward enhancing public transport, cycling, and walking options [66]. The provision of transportation amenities underscores the significance of elevating residents' quality of life to establish a socially sustainable community [5]. In the pursuit of social sustainability, the role of public transport remains essential for urban and metropolitan settings [67]. Transportation facilities are essential components of urban systems aimed at fostering a sustainable city [68].

Dhaka city's transportation landscape is marked by persistent traffic congestion, discomfort, safety concerns, and subpar air quality [69]. Despite the overwhelming need, the metropolis of Dhaka continues to grapple with a substantial deficit in adequate and quality public transport options and pedestrian pathways [70]. The unchecked expansion of urban areas further strains the capacity to deliver essential municipal services, including transportation infrastructure, particularly evident in Dhaka [12]. Widespread dissatisfaction among users of public transport pervades the neighborhoods of Dhaka city, underscoring a notable absence in the performance of transport sustainability [8, 20]. The city of Dhaka has experienced a chaotic and intense spread of horizontal densification, emphasizing the imperative of an integrated approach to residential planning that prioritizes the provision of public transport facilities and associated amenities [8].

Sufficient transportation infrastructure cannot be overstated in developing sustainable urban systems, crucial for fostering a sustainable city [68]. Dhaka city's developmental strategy strongly emphasizes enhancing public transport services while promoting walking and cycling alternatives [40]. The Dhaka city plan highlights the lack of coordination between different transport modes [71]. Additionally, the government has initiated the “Bus Rapid Transit System (BRT System)” as a sustainable urban transport initiative to provide Dhaka with safe, affordable, comfortable, and environmentally friendly transportation solutions [69]. However, existing literature suggests that the issue of transportation availability within Dhaka city demands heightened attention to improve services for its residents, thereby contributing to the city's sustainability. Moreover, this study reinforces the notion that the availability of transportation significantly and positively impacts socially sustainable urban growth within the context of Dhaka city.

Hence, based on residents' opinions and statistical analysis, it is evident that all indicators of transportation availability need to be considered by the relevant authorities in Bangladesh to ensure a sustainable city. Furthermore, these findings are similarly significant for Dhaka and other cities of developing regions such as Kolkata, Delhi, Shanghai, Beijing, Mumbai, and Cairo, and future researchers are advised to adopt the same approach to explore other cities in Bangladesh facing similar challenges. Therefore, authorities can leverage these findings to assess their transportation infrastructure, and availability, facilitating progress toward sustainability.

Transportation availability plays a crucial role in fostering social sustainability, which is paramount for the overall sustainability of urban environments. Regrettably, this critical aspect often goes unnoticed in the development plans of many cities in developing regions including Dhaka. Hence, it is imperative for all stakeholders, including city authorities, to recognize the present state of transportation availability and its profound influence on the advancement of socially sustainable urban development. Through gaining a deeper understanding of these dynamics, we are empowered to create a socially sustainable urban landscape that benefits both current inhabitants and future generations. This endeavor is crucial to building a better, more equitable urban environment for all.

The findings of this study underscore a concerning trend: all aspects related to transportation availability have contributed to a notable dissatisfaction among Dhaka city dwellers. The current transport availability does not align with socially sustainable urban development requirements. Furthermore, the statistical analysis elucidated that each indicator of transportation availability positively influences the advancement of SSUD within Dhaka city. It underscores the pivotal role of transportation availability as a cornerstone of social sustainability, crucial for progressing in socially sustainable urban environments. Therefore, the findings of this study contribute to Dhaka City Corporation, policymakers, urban planners, and implementing agencies to find out the gap between the current transport availability and its impact on socially sustainable urban development. Also, it contributes to the Urban Sector Policy 2011 in Bangladesh by including all indicators of transport availability. Only through their collaborative efforts can a socially sustainable Dhaka be realized, paving the path for a brighter, more equitable future for all its inhabitants.

Notably, this research had limitations. Our study is limited to a small sample size of 564 replies, which suggests that future studies might benefit from a more extensive dataset to get more depth and robustness. Second, quantitative methods were used in the study. Future studies could integrate qualitative research methods to enrich the exploration of urban social sustainability, offering more profound insights into the multifaceted dimensions at play. Thirdly, it is essential to highlight the geographical focus of this study on Dhaka city. Recognizing the broader relevance of data insights to Dhaka and other rapidly urbanizing cities, future researchers are encouraged to adopt a similar approach in exploring other similar cities. Fourthly, this study utilized four items from existing literature to gauge transportation availability. Future researchers may find value in constructing a dedicated index tailored to the specific context of the city, potentially yielding fresh perspectives and insights within this field of study.