This dissertation is concerned with developing new methods for exploring the pressing problems of uncertainty, Environmental Justice, and tolling as they relate to long-range transportation planning. While these topics are seemingly disparate, much of the work in this dissertation is motivated by the increasing number of roadway projects concessioned to the private sector, and the lack of tools available for evaluating the impact of such agreements on the public given high levels of uncertainty over the length of the contracts and concern for the welfare of traditionally underserved population groups. These issues will be considered separately and together, offering insights into how transportation investment decisions can be improved. To this end, the impacts of considering long-range uncertainty in the traffic assignment model as well as in an integrated transportation and land use model (ITLUM) are assessed in terms of the effects on network performance measures and roadway improvement decisions. A new method for accounting for correlations between the future travel demands of origin-destination zone pairs is developed for the traffic assignment problem that can more effectively model the effects of potential economic changes. Results showed that neglecting correlations can lead to measures of variance of future total system travel time that range from underestimating the actual measure by seventy-five percent to overestimating it by one hundred percent, and to different selections for a network improvement project in up to fifty percent of all scenarios. Uncertainty in a basic ITLUM is considered more broadly, incorporating probability distributions for population and employment inputs as well as several travel demand model parameters, and examining how the choice of performance measure impacts the effect of uncertainty on the decision of where to increase system capacity. Comparing the network improvement projects selected when uncertainty is considered to a deterministic analysis, showed differences in up to 25% of scenarios. Challenges of considering Environmental Justice, a type of group-based equity that is required for metropolitan transportation plan compliance in the United States, are explored, particularly with regard to appropriately defining the term equity for the analysis. Several of these potential definitions are then transformed into objective functions for use in a new formulation of the user equilibrium-based discrete network design problem. A multi-objective genetic-algorithm solution method is developed to solve the problem efficiently, and insights are revealed into how different definitions of equity can lead to different decisions. The following objectives, both commonly used in practice, were found to be conflicting: 1) minimizing the difference in post-improvement performance across populations and 2) minimizing the difference across populations in the change in performance due to improvements. The problem of roadway tolling is first examined from the perspective of a private sector toll road operator seeking to maximize the asset's value by exercising flexibility. A stochastic recourse model is developed to account for the first stage investment decision and the second stage decisions to alter network capacity and toll rates. The flexibility to engage in non-compete clauses whereby the public sector cannot improve competing roadways, and also to improve feeder links in the surrounding network were found to play important roles in asset valuation. The value of having these options was found to increase with an increase in uncertainty of future demand, complexity of network structure, and the consequence of failure to meet debt obligations. The three original issues of uncertainty, Environmental Justice, and tolling are woven together into the development of a new method for determining the maximum toll rate that can be applied in a private sector operation scenario (first option) such that each group within the population, as defined for analysis of Environmental Justice, is no worse off than if the road had been constructed by the public sector without tolling (second option). Three stochastic dominance criteria are implemented to find the toll rate at which the first option dominates the second given uncertainty about the future travel demand. Findings suggest that there may be many toll rates that equate the benefits resulting from the two options, so the minimum rate is considered the optimal one. The difference in benefits to the groups was found to increase with increasing value of time, and the differences in optimal toll rates using each of the three dominance criteria increased similarly. The analytical tools developed in this dissertation, and the resulting insights obtained should offer significant contributions to several areas of long-range transportation planning, particularly informing the process of concessioning roadways to private entities, developing a transportation system that is robust to future uncertainty, and ensuring that Environmental Justice criteria is met by considering the transportation needs of each group within the population. / text

published_or_final_version / Urban Planning and Design / Master / Master of Science in Urban Planning

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For organizations such as state departments of transportation, other public agencies, or private companies, adopting a new approach to procure services for delivery of construction projects requires significant organizational changes; modifications to both their work processes and existing organizational structures may be needed. These adjustments, encompassing many different aspects of the organization's interests, must occur for the change initiative to be successfully put into practice. In this research, the adoption of integrated project delivery methods within the transportation project sector is investigated to better understand the dynamics of this change. In the context of this study, an Owner's project delivery strategy is defined as the set of project delivery methods that are adopted for delivering capital projects. This dissertation presents findings from a study of Public Owner organizations that have implemented the designbuild method for delivering highway projects. Using as a case study the new $1.3 billion SH-130 tolled expressway project in Central Texas, the author analyzed project documentation and conducted many interviews with individuals affiliated with owner, legal, engineering consultants, and contractors. Findings suggest that project representatives institutionalize practices and routines connected to the new approach by adapting to new challenges, rather than "overwriting" previously existing practices. Similarly, the institutionalization of innovative approaches to project delivery happens concurrently with a deinstitutionalization of the previous approaches. Building upon these findings, a conceptual framework is presented for helping Owner organizations implement change in their project delivery strategy. The proposed conceptual framework is based upon both existing published literature and interviews with managers involved in implementing a strategic change in project delivery strategy. This framework was further refined by making a comparative study of four transportation projects in the United States. In addition, a detailed implementation framework was validated and further developed through a Delphi study with representatives from several organizations whose major responsibilities and experiences include the management of change in procurement approach. Findings from these studies, including application to the construction industry and other industries are presented.

No description available.

Urban VANET (Vehicular Ad hoc NETworks) performance optimization concerns the improvement of wireless signal quality between two arbitrary selected nodes moving within along city streets. It includes three procedures: VANET architecture modeling; wireless signal simulation; and signal quality optimization techniques. The first procedure converts real-world map data into a network graph according to the requirement of the optimization algorithm. The second step analyzes a communication route between two network nodes and calculates received signal quality with the information provided by the network model. The final operation optimizes the signal quality to an expected level by choosing appropriate communication route between two wireless nodes. In this thesis, three optimization techniques are presented: EP (Evolutionary Programming), SG (Stochastic Geometry) and SW (Small World). EP is a widely applied optimization strategy based on Darwin’s natural selection and evolution theory. It is effective with an enormous number of data support, and it can provide detailed route information. However, it requires enough time to evolve to an optimal solution. SG is a statistical tool to analyze points’ distribution within a multi-dimensional space, and it was recently applied on wireless network analysis. Given the distribution characteristics of an urban area, SG can calculate average data loss rate of a communication route. However, it cannot provide detailed route information. SW is a widely accepted model to represent people’s relationship in social networks, and it can be used in VANET analysis. SW provides a simplified network architecture compared with EP an SG. However, it requests additional long-range communication equipment and consumes more energy. The thesis is divided into three parts. Chapter 1 introduces the history of VANET and its architecture (in this research, it is a combination of Ad hoc network and WSN (Wireless Sensor Network)). Chapter 2 and 3 presents literature review of EP and SG. Chapter 4, 5, and 6 discusses how to implement EP, SG and SW on Boston VANET. At the end of each chapter, a conclusion is presented and a discussion on the author’s contribution is given.

M. Tech. Civil Engineering. / The purpose of this study is to evaluate the effect of an increase in stone size and volume on asphalt. This will be limited to asphalt surfacing with a viewpoint to the coal haulage industry.

This thesis investigates the use of Discrete Element Modelling (DEM) to simulate the elastic and viscoelastic deformation behaviour of an asphalt mixture. A numerical specimen preparation procedure has been developed to produce specimens with an isotropic stress and correct volumetrics. Stone mastic asphalt has been chosen in this project because of its high content of coarse aggregate and binder-rich mortar. A range of uniaxial compression tests have been undertaken in the laboratory under various loading speeds and stresses. The axial stress, axial strain and radial strain were recorded during the tests. The peak stress is found to be as a power-law function of the strain rates for the asphaltic material. Elastic contact properties have been used to investigate the effect of particle number and location, loading speed, normal and shear contact stiffness. The Poisson's ratio was found to increase with the ratio of normal to shear contact stiffness but was independent of the stiffnesses. The Young's modulus was found to be dependent on both normal and shear stiffnesses, in agreement with previous work on idealised asphalt mixtures. The Burger's model was introduced to give time-dependent stiffness for the viscoelastic modelling. The Burger's model was implemented to give moment and torsional resistance as well as in direct tension and compression. To reduce the computational time in the creep simulations, the effect of scaling both viscosities in the Burger's model to simulate a shorter time, have been investigated. The effects of each parameter on the deformation of asphalt mixture were also investigated. The stress-strain response for the laboratory tests and the simulations were recorded. The results show good agreement when the bond strengths in the model are made to be a function of strain rate for both constant strain rate and creep conditions. Both normal and Weibull distributions have been used for the bond strengths between the aggregate particles. The constant strain rate tests results were proved to be independent of the bond strength variability and position of particles, while the creep tests results were dependent on the hand strength variability and position of particles. This is in good agreement with experimental tests: different specimens at the same stress level gave variability in the creep behaviour, at higher stress levels. Bond breakages were recorded during the simulations to investigate the micromechanical deformation behaviour of asphalt mixtures. It was found that a well-defined rupture at higher stress levels coincided with the maximum rate of bond breakage. The modified Burger's model has therefore proven to be a useful tool in modelling the moment and torsional resistance at particle contacts in an asphalt mixtures, in order to correctly predict observed behaviour.

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No description available.