Infrastructure Engineering - Research Publications
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ItemPrivacy- and context-aware release of trajectory data(ACM, 2020-03)The availability of large-scale spatio-temporal datasets along with the advancements in analytical models and tools have created a unique opportunity to create valuable insights into managing key areas of society from transportation and urban planning to epidemiology and natural disasters management. This has encouraged the practice of releasing/publishing trajectory datasets among data owners. However, an ill-informed publication of such rich datasets may have serious privacy implications for individuals. Balancing privacy and utility, as a major goal in the data exchange process, is challenging due to the richness of spatio-temporal datasets. In this article, we focus on an individual's stops as the most sensitive part of the trajectory and aim to preserve them through spatio-temporal perturbation. We model a trajectory as a sequence of stops and moves and propose an efficient algorithm that either substitutes sensitive stop points of a trajectory with moves from the same trajectory or introduces a minimal detour if no safe Point of Interest (POI) can be found on the same route. This hinders the amount of unnecessary distortion, since the footprint of the original trajectory is preserved as much as possible. Our experiments shows that our method balances user privacy and data utility: It protects privacy through preventing an adversary from making inferences about sensitive stops while maintaining a high level of similarity to the original dataset.
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ItemThe Impact of Flexible Platoon Formation Operations(Institute of Electrical and Electronics Engineers (IEEE), 2020-06)Vehicle platooning, a coordinated vehicle movement strategy, has been proposed to address a range of current transport challenges such as traffic congestion, road safety, energy consumption and pollution. While the current literature mainly focuses on platoon control strategies and intra-platoon communication, comparatively little work is done on how to form these platoons. Literature assumes platoon formation by tail merge which is sufficient only for planned formation on a ramp or at a ramp-highway junction. In this article we study the impact of three different merge operations, namely front, middle, and tail merge. The efficiency of these operations is analyzed under different scenarios, varying the vehicles speed adjustment strategy, traffic density, and the density of mergeable vehicles. The impact of the merge operations is represented in terms of merge time, merge distance, average traffic speed, and merge success rate. Our experiments show that in an ideal no traffic scenario, the middle merge is costlier in terms of merge time for the same merge distance whereas in the presence of traffic middle merge helps is quick platoon formation on an average in a higher traffic density in particular. This insight should provide a more flexible toolkit for planning a platoon formation.
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ItemAnalysis of an Ad-hoc Platoon Formation and Dissolution Strategy on a Multi-lane Highway.(University of Auckland, 2019-01-01)Vehicle platooning has become popular in the recent Intelligent Transportation System (ITS) research. The literature typically assumes a planned formation and dissolution of platoons, mostly at source and destination. In contrast, this research considers platoons that can be formed on the fly. We investigate a greedy type of platoon formation with no particular order of destinations of the platoon members. This greedy formation allows a quick formation of the platoon but imposes an overhead of platoon rebuild cost when platoon members leave. The question arises whether this greedy formation and dissolution of platoons can preserve the original fuel benefit of platooning. To investigate this question, this research implements such a strategy and provides a generic guideline for fuel-efficient ad-hoc platooning
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ItemImprecise Navigation(SpringerLink, 2003)Conventional models of navigation commonly assume a navigation agent's location can be precisely determined. This paper examines the more general case, where an agent's actual location cannot be precisely determined. This paper develops a formal model of navigation under imprecision using a graph. Two key strategies for dealing with imprecision are identified and defined: contingency and refinement. A contingency strategy aims to find an instruction sequence that maximizes an agent's chances of reaching its destination. A refinement strategy aims to use knowledge gained as an agent moves through the network to disambiguate location. Examples of both strategies are empirically tested using a simulation with computerized navigation agents moving through a road network at different levels of locational imprecision. The results of the simulation indicate that both the strategies, contingency and refinement, applied individually can produce significant improvements in navigation performance under imprecision, at least at relatively fine granularities. Using both strategies in concert produced significant improvements in performance across all granularities.
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ItemLocation privacy and location-aware computing(CRC Press, 2006)
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Item"Simplest" paths: automated route selection for navigation(Springer, 2003)Numerous cognitive studies have indicated that the form andcomplexity of route instructions may be as important to human navigatorsas the overall length of route. Most automated navigation systemsrely on computing the solution to the shortest path problem, and not theproblem of finding the “simplest” path. This paper addresses the issueof finding the “simplest” paths through a network, in terms of the instructioncomplexity. We propose a “simplest” paths algorithm that hasquadratic computation time for a planar graph. An empirical study ofthe algorithm’s performance, based on an established cognitive model ofnavigation instruction complexity, revealed that the length of a simplestpath was on average only 16% longer than the length of the correspondingshortest path. In return for marginally longer routes, the simplest pathalgorithm seems to offer considerable advantages over shortest paths interms of their ease of description and execution. The conclusions indicateseveral areas for future research: in particular cognitive studies areneeded to verify these initial computational results. Potentially, the simplestpaths algorithm could be used to replace shortest paths algorithmsin any automated system for generating human navigation instructions,including in-car navigation systems, Internet driving direction servers,and other location-based services.
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ItemInformation dissemination in mobile ad-hoc geosensor networks(SPRINGER-VERLAG BERLIN, 2004)
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ItemA formal model of obfuscation and negotiation for location privacy(Springer, 2005)Obfuscation concerns the practice of deliberately degradingthe quality of information in some way, so as to protect the privacy ofthe individual to whom that information refers. In this paper, we arguethat obfuscation is an important technique for protecting an individual’slocation privacy within a pervasive computing environment. The papersets out a formal framework within which obfuscated location-based servicesare defined. This framework provides a computationally efficientmechanism for balancing an individual’s need for high-quality informationservices against that individual’s need for location privacy. Negotiationis used to ensure that a location-based service provider receivesonly the information it needs to know in order to provide a service ofsatisfactory quality. The results of this work have implications for numerousapplications of mobile and location-aware systems, as they providea new theoretical foundation for addressing the privacy concerns thatare acknowledged to be retarding the widespread acceptance and use oflocation-based services.
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ItemSimulation of obfuscation and negotiation for location privacy(Springer, 2005)Current mobile computing systems can automatically sense and communicatedetailed data about a person’s location. Location privacy is an urgent researchissue because concerns about privacy are seen to be inhibiting the growthof mobile computing. This paper investigates a new technique for safeguardinglocation privacy, called obfuscation, which protects a person’s location privacy bydegrading the quality of information about that person’s location. Obfuscation isbased on spatial imperfection and offers an orthogonal approach to conventionaltechniques for safeguarding information about a person’s location. Imprecisionand inaccuracy are two types of imperfection that may be used to achieve obfuscation.A set of simulations are used to empirically evaluate different obfuscationstrategies based on imprecision and inaccuracy. The results show that obfuscationcan enable high quality of service in concert with high levels of privacy.
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ItemA spatiotemporal model of obfuscation strategies and counter strategies for location privacy( 2006)Safeguarding location privacy is becoming a critical issue in location based services and location-aware computing generally. Two drawbacks of many previous models of location privacy are: 1) the models only consider a person’slocation privacy protection, but not the invasion of location privacy by external agents; and 2) the models are static and do not consider the spatiotemporal aspectsof movement. We argue that, to be complete, any model of location privacy needs to enable the analysis and identification of techniques both to protect and toinvade an individual’s location privacy over time. One way to protect an individual’s location privacy is to minimize the information revealed about a person’s location, termed obfuscation. This paper presents an explicitly spatiotemporalmodel of location privacy that models a third party’s limited knowledge of a mobileindividual’s location. We identify two core strategies that a third party canuse to refine its knowledge, so potentially invading that mobile individual’s locationprivacy. A global refinement strategy uses the entire history of knowledgeabout an agent’s location in a single step. A local refinement strategy iterativelyconstructs refined knowledge over time.We present a formal model of global andlocal refinement operators, and show how this formal model can be translatedinto a computational model in a simulation environment.