The urban spatial structure of employment and its impacts on transportation and urban development : a case study of Dhaka megacity

In recent times, the Asian region has become a central theme in debates on economic growth and urbanisation. Asian urbanisation shows a distinctive character with accumulation of resources to a few selected cities and, in turn, rapid growth to megacity status. The nature and the scale of urbanisation towards these megacities has posed complex and demanding challenges for planners and policymakers dealing with issues of sustainable urban development. One of the most demanding challenges is inadequate understanding of the urban spatial structure allocation of activities in the urban landscape of megacities. There are several schools of thoughts on the urban structure of North American, European and Australian cities and what types of urban form may generate more longer term urban and transport oriented sustainable solutions. Much of the western debate is based on solid empirical analyses that utilize very rich data from census sources, journey-to-work statistics and land-use distributions data that enables modelling of future urban growth and urban structure patterns for analysis of more optimal outcomes. By contrast, similar empirical analyses of Asian megacities are few and far between; mainly due to the unavailability or absence of similar data that is relatively up-to-date for enabling explorations of urban spatial structure. This thesis attempts to make a contribution to this critical gap by utilising various official data sets that have recently been made available by consulting teams and authorities in the megacity of Dhaka, Bangladesh.The main focus of this thesis is an examination of the urban spatial structure of the megacity of Dhaka, and it argues that the fundamental underlying spatial structure of this city is likely to be very different to that of western cities due to different levels of development and socio-economic conditions. The nature and patterns of this underlying urban spatial structure are assessed through a detailed examination of employment distribution and its travel related impacts, in particular the functional relationships between the residential locations of workers, their job destinations and their actual journey-to-work trip patterns. This, in turn, allows assessment of implications for present and future sustainability of the city, and whether a different spatial structure from a policy and planning perspective may accommodate more sustainable growth into the future. An attempt is made to identify if the urban spatial structure of Dhaka is characterised as being monocentric, polycentric or falls along a continuum between the two extreme spatial structures, and to compare this with the identified structure of some other Asian megacities.One key aim of this research is to contribute to the debates on the role of future urban spatial structure in generating a sustainable future for Dhaka. The approach taken in the thesis is that the optimum way of making this contribution is to explore and understand the land use-transport dynamics of Dhaka megacity and the potential development options for the city. Several growth scenarios are generated for the year 2024, and their travel consequences are estimated using transportation models. This research utilises very rich and diverse datasets for Dhaka which includes the national census, data collected for the urban master plan and data collected and generated as part of the strategic transportation studies carried out in the late 2000s. The results strongly indicate that the megacity of Dhaka is characterised by an extended monocentric urban structure as opposed to a polycentric one. There do exist very high density employment centres but these are located in relatively close proximity to the main city centre and found in high density areas that surround the main city. The three employment centres located in the outer ring dominate their respective catchment areas but have relatively low densities of employment. These three centres have the potential to develop into fully functional polycentric centres in the future.The results also suggest that Dhaka is likely to experience higher levels of congestion and pollution unless job decentralisation occurs to the 19 identified employment centres along with more sustainable transportation arrangements. Estimates are generated of significant changes in travel costs and vehicle emissions under different decentralisation scenarios. The analysis suggests that spatial decentralisation of employment might increase average commuting length to the employment centres in the outer ring as more people would travel to outskirts. However, it would reduce up to around 30% of vehicle emissions from commuting in the main city. In other words, job decentralisation redistributes emissions and, hence, would improve air quality in the main city. This study calls for proper policy and planning initiatives to expedite job re-distribution to potential job centres outside the main city and to enhance the growth of these centres to serve the megacity in a more sustainable way