|Title:||Design of urban rail corridor over time : for cities with high population densities and growth uncertainties|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Local transit -- Planning
|Pages:||133 pages : color illustrations|
|Abstract:||To alleviate traffic congestion problems, urban rail transit lines are being built continuously in many metropolitan cities in China. These Chinese cities, like Hong Kong and Shanghai, have significantly higher population densities in urban areas, in contrast with European and American cities. Traditional models for planning of urban rail transit lines are mainly static models and usually developed for European and American cities with low population densities. The research presented in this thesis aims to propose analytical models of optimising urban rail transit lines over time, for cities with high population densities. This thesis contributes to the literature of urban rail transit lines design problems in the following several aspects but with focus on a linear urban transportation corridor for a monocentric city. Firstly, an optimisation model is proposed to investigate over-year interaction between endogenous population densities and financial performance of a candidate rail transit line in Chapter 3. The proposed optimisation model is a bi-level programming model, with a lower level problem formulated as a user equilibrium model, and an upper level problem formulated as an urban rail transit line design model over time. Traditional models for design of urban rail transit lines were developed with objectives of travel time or cost minimisation for a particular design year, while the planning data of the design year is given and fixed. By contrast, the optimisation objective of the mathematical programming model proposed in Chapter 3 is the social welfare maximisation for a period of time horizon. It was found in Chapter 3 that a lack of integration of short-term decision variables, headway and fare, may result in excessive investments for the long-term rail construction, namely the increase of optimal rail line length. More population were attracted to live in vicinity of the candidate transit line while rail service was supplied. With extension of rail service over years, more population chose to move gradually from residential locations of CBD to residential locations of suburban areas. The candidate rail transit line can make population densities more decentralised over time, namely more population distributed at residential locations of suburban areas. Secondly, implementation adaptability of a candidate rail transit line is explored over years in Chapter 4. Adaptability is defined as the ability of the system to adapt to external changes, while maintaining satisfactory system performance. Implementation adaptability gives authorities and/or operators to fast-track or defer the future investment on the candidate rail transit line for several years, if necessary. To obtain an adaptable candidate rail transit line suitable to accommodate external changes over the years, it is required that the candidate rail transit line can be fast-tracked or deferred several years. For example, if the total supply cost of the candidate rail transit line is lower than that predicted in the previous feasible study, the candidate rail transit line can be fast-tracked accordingly. Nonetheless, less attention was given to examine the implementation adaptability of urban rail transit line in the literature. This is mainly due to the fact that most of the traditional models were static models and developed for a particular design year. To address the implementation adaptability issue for design of the candidate rail transit line over time, three alternatives are explored in Chapter 4: fast-tracking several years, deferring several years and do-nothing-alternative (DNA).|
The analytical solutions of the optimal years, to be fast-tracked or deferred, are obtained by the proposed model in Chapter 4. Sensitivity tests for the optimal project start time are conducted with respect to the yearly variation of the total population and annual interest rate. Thirdly, the effects of spatial and temporal correlation of population densities on the design of an urban rail transit line over years are investigated in Chapter 5. Population densities at different residential locations along a candidate rail transit line are correlated. Population growth in one location can positively influence the population growth in adjacent location. For instance, for a given total population along a linear rail transportation corridor, more households choose the central business district (CBD) to live, leaving fewer for suburban communities and new towns in the outlying locations. In this case, a negative spatial correlation exists between population densities at the CBD, and the suburban communities and new towns. A closed-form mathematical programming model is proposed in Chapter 5 to investigate the effects of spatial and temporal correlation of population densities on the design of the candidate rail transit line. In the proposed model, the optimisation objective is the budget social welfare maximisation. The decision variables include rail line length, rail station number and project start time of the candidate rail transit line. The analytical solutions of the above decision variables are derived explicitly. Finally, choices of alternative travel modes for households are incorporated in Chapter 6 to investigate the effects of households' prospect theory based travel behaviour over time for design of rail transit line in the liner transportation corridor. The available travel modes consist of car, bus, rail and park-and-ride. The prospect theory based analytical mathematical model proposed in Chapter 6 is proved to be convex, and the existence and uniqueness of solutions are guaranteed. It was found that the population density within the linear transportation corridor was closely correlated with the modal split results of households and the financial performance of the candidate rail transit line. To certain extent, the park-and-ride may not be suitable for cities with high population densities such as Hong Kong. This research appears to be the first devoted exclusively to the topic of using analytical models for investigation of urban rail design problems over time, with particular attention on the effects of population density by location along the linear transportation corridor over years. The transportation authorities could make use of the proposed models for proving useful insights in order to give the guidelines and/or strategies for design of the urban rail line over time in the urban area particularly in the corridor with potential for high population density but uncertainty in population growth in the future.
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