• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 249
  • 69
  • 34
  • 4
  • 4
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 447
  • 447
  • 122
  • 101
  • 71
  • 68
  • 63
  • 50
  • 43
  • 42
  • 42
  • 39
  • 39
  • 35
  • 32
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
351

Contribution à l'analyse de la mobilité: Développement d'un modèle intégré de données nécessaires à l'analyse de la mobilité urbaine: MIDAM

Danoh, Charlemagne 11 June 2007 (has links)
Traiter les problèmes que pose la mobilité urbaine aujourdhui nécessite entre autres, lélaboration dune banque de données complète, capable de supporter les analyses qualitatives et quantitatives du système de transport et den évaluer lévolution en rapport aux éventuels changements de lensemble du système urbain. Les données relatives au domaine des transports sont indispensables à lalimentation des modèles de trafic, à lanalyse de la mobilité globale et aux suivis et à la gestion des conditions découlement du trafic au travers dun réseau de transport donné, dans le temps et dans lespace (Taylor M. et al, 1996; Bonnel P., 2004). Cependant, ces données sont très souvent collectées séparément selon les objectifs poursuivis par le planificateur. En effet, la planification urbaine ou la planification des transports en commun présente des objectifs différents de celle, par exemple, des trafics routiers et autoroutiers (Meyer M. et al, 2001). Ces planifications seffectuent généralement sans trop tenir compte des interactions qui sétablissent entre elles. Ainsi, fournir des solutions adéquates aux problèmes de mobilité urbaine, nécessite la prise en considération des aspects environnementaux et de lensemble des caractéristiques de lespace urbain : le système de transport et le système des localisations et des activités socio-économiques (Cancalon F. et al, 1991 ; Bonnel P., 2004). Les solutions ainsi générées doivent provenir dune approche intégrée de la planification des transports (Meyer M. et al, 2001). De plus, il a été pris en considération des éléments de modélisation de données (les GIS-T models) développés par (Dueker et al, 1997). Cest dans cette optique que cette recherche se propose dappréhender la question de la mobilité urbaine par une approche systémique de lespace urbain. Celui-ci sera caractérisé par lensemble des données qui le constitue afin de mettre en lumière les relations qui sous tendent la structure urbaine en question. Il sera ainsi développé un modèle intégré de données nécessaires à lanalyse de la mobilité urbaine : MIDAM. Ensuite, sur la base de MIDAM et de la synthèse de la littérature en matière de données « transports » et sur les logiciels de gestion de trafic, il a été possible de démontrer la faisabilité dun outil intégré « VISUTRANS » pour le suivi des politiques de transports ; la modélisation et les effets des transports urbains sur lenvironnement. Enfin, une méthodologie pratique quant à la manière dappréhender la mobilité urbaine est proposée avec pour cas dapplication la ville de Liège - Belgique.
352

An assessment tool for the appropriateness of activity-based travel demand models

Butler, Melody Nicole 13 November 2012 (has links)
As transportation policies are changing to encourage alternative modes of transportation to reduce congestion problems and air quality impacts, more planning organizations are considering or implementing activity-based travel demand models to forecast future travel patterns. The proclivity towards operating activity-based models is the capability to model disaggregate travel data to better understand the model results that are generated with respect to the latest transportation policy implementations. This thesis first examines the differences between the two major modeling techniques used in the United States and then describes the assessment tool that was developed to recommend whether a region should convert to the advanced modeling procedures. This tool consists of parameters that were decided upon based on their known linkages to the advantages of activity-based models.
353

An Integrated Decision-Making Framework for Transportation Architectures: Application to Aviation Systems Design

Lewe, Jung-Ho 19 April 2005 (has links)
The National Transportation System (NTS) is undoubtedly a complex system-of-systems---a collection of diverse 'things' that evolve over time, organized at multiple levels, to achieve a range of possibly conflicting objectives, and never quite behaving as planned. The purpose of this research is to develop a virtual transportation architecture for the ultimate goal of formulating an integrated decision-making framework. The foundational endeavor begins with creating an abstraction of the NTS with the belief that a holistic frame of reference is required to properly study such a multi-disciplinary, trans-domain system. The culmination of the effort produces the Transportation Architecture Field (TAF) as a mental model of the NTS, in which the relationships between four basic entity groups are identified and articulated. This entity-centric abstraction framework underpins the construction of a virtual NTS couched in the form of an agent-based model. The transportation consumers and the service providers are identified as adaptive agents that apply a set of preprogrammed behavioral rules to achieve their respective goals. The transportation infrastructure and multitude of exogenous entities (disruptors and drivers) in the whole system can also be represented without resorting to an extremely complicated structure. The outcome is a flexible, scalable, computational model that allows for examination of numerous scenarios which involve the cascade of interrelated effects of aviation technology, infrastructure, and socioeconomic changes throughout the entire system.
354

Quantifying the benefits of ancillary transportation asset management

Akofio-Sowah, Margaret-Avis 16 November 2011 (has links)
Historically, transportation asset management has focused on roadways and bridges, but more recently, many agencies are looking to extend their programs to ancillary assets such as traffic signs and guardrails. This thesis investigates the state of practice of managing these assets in order to assess the data and system needs for successful program implementation, and further reviews the opportunities for making a business case for formal management procedures based on quantified benefits of managing ancillary assets. The asset classes, selected from a review of asset management literature, include culverts, earth retaining structures, guardrails, mitigation features, pavement markings, sidewalks and curbs, street lights, traffic signals, traffic signs and utilities and manholes, with data as an information asset. Findings from a literature review showed that a number of agencies have made substantial efforts to manage their ancillary transportation assets; however, methods and practices vary. Specific state and municipal agencies identified from the literature review were surveyed for further details on their practices. The survey results show significant knowledge gaps in data collection cost estimates, and cost savings from the implementation of a transportation asset management program for ancillary assets. Finally, this work evaluates the opportunities to quantify the benefits of ancillary transportation asset management, indicating several challenges due to a lack of the data needed. The results obtained highlight the current state of practice, revealing opportunities and challenges for improving the management of ancillary transportation assets.
355

Simultanes Routen- und Verkehrsmittelwahlmodell

Vrtic, Milenko 18 April 2004 (has links) (PDF)
Bei verkehrspolitischen und infrastrukturellen Massnahmen folgen als wesentliche Nachfrageveränderungen vor allem Routen- und Verkehrsmittelwahleffekte. Mit der Anwendung der sequentiellen Routen- und Verkehrsmittelwahlmodelle, ist bei solchen Massnahmen aus verschiedenen Gründen eine konsistente und gesamthafte Gleichgewichtslösung nicht möglich. Das Ziel dieser Untersuchung war, ein konsistentes und verfeinertes Verfahren zu entwickeln, mit dem die Routen- und Verkehrsmittelwahl simultan bzw. in einem Schritt als eine Entscheidung berechnet werden kann. Neben dem Gleichgewicht bei der Verteilung der Verkehrsnachfrage auf die Alternativen, war die konsistente Schätzung der Modellparameter für die Bewertung von Einflussfaktoren bei den Entscheidungen hier eine weitere wichtige Anforderung. Das Modell ist in der Lage, ein realitätsentsprechendes Verhalten der Verkehrsteilnehmer, sowohl bei schwach, als auch bei stark belasteten Strassennetzen, zu beschreiben. Die unterschiedliche Wahrnehmung der Reisekosten der Verkehrsteilnehmer und die Netzüberbelastungen werden durch ein stochastisches Nutzergleichgewicht abgebildet. Das entwickelte Verfahren ermöglicht es: - die Nachfrageaufteilung mit einem konsistenten Gleichgewicht zwischen Verkehrsangebot und Verkehrsnachfrage zu berechnen. Dabei wird ein Gleichgewicht nicht nur innerhalb des Strassen- oder Schienennetzes, sondern zwischen allen verfügbaren Alternativen (unabhängig vom Verkehrsmittel) gesucht. - durch die iterative Kalibration der Modellparameter und die Nachfrageaufteilung ein konsistentes Gleichgewicht zwischen den geschätzten Modellparametern für die Nutzenfunktion und der Nachfrageaufteilung auf die vorhandenen Alternativen (Routen) zu berechnen. - mit einem stochastischen Nutzergleichgwicht die unterschiedliche Wahrnehmung der Nutzen bzw. der generalisierten Kosten der Verkehrsteilnehmer bei der Nachfrageaufteilung zu berücksichtigen. - die Auswirkungen von Angebotsveränderungen auf die Verkehrsmittelwahl und Routenwahl durch simultane Modellierung der Entscheidungen konsistent und ohne Rückkoppelungschritte zu berechnen.
356

Safety at highway-railroad crossings : a case study of the Austin-San Antonio corridor

Zankowski, Jennifer Jaye 25 July 2011 (has links)
For over a decade proposals for connecting the metropolitan areas of Austin and San Antonio, Texas via passenger rail have been studied. In the Texas Department of Transportation’s 2010 Rail Plan several ideas, including high-speed rail, regional Amtrak service, and a new passenger rail service have been proposed as a means to provide an alternate mode of transportation along the I-35 corridor. Union Pacific Railroad currently owns and operations a rail line that connects the Austin and San Antonio metropolitan areas; each of the passenger rail projects proposes sharing this corridor with Union Pacific. A literature review reveals that a key factor in negotiating with a freight railroad for shared use of a corridor is safety. One element of the safety risk analysis is the evaluation of at-grade highway-railroad crossing. This study discusses the Austin-San Antonio corridor, its current mobility challenges and the proposed passenger rail projects. It then discusses rail safety as expressed in the literature and provides background about safety at highway-railroad crossings. Crossing inventory and accident data, as maintained by the Federal Railroad Administration (FRA), is then analyzed using regression modeling in an attempt to better understand the relationship between the physical and operational characteristics of highway-railroad crossings and accidents on corridors shared by freight and passenger rail. It analyzes a five-year accident history (2005 to 2009) from of a sample of shared use highway-rail crossings throughout the US. The findings are then used to analyze the at-grade highway-railroad crossings along the Austin-San Antonio corridor. And finally, the implications of the findings are discussed. The findings of this report recommend that characteristics of the built environment such as land use, number of traffic lanes, and function classification of the roadway should be considered when assessing accident risk at highway-railroad crossings. In addition, this analysis reveals the need for a way to better measure safety risks at private highway-railroad crossings. / text
357

Ein integriertes Verkehrsnachfrage- und Bewertungsmodell

Winkler, Christian 09 January 2012 (has links) (PDF)
In dieser Arbeit wird ein Modell zur integrierten Verkehrsnachfrage- und Nutzenberechnung für den privaten Personenverkehr entwickelt, mit dem eine harmonisierte Bewertung der entscheidungsrelevanten Aufwände der Verkehrsteilnehmer in der Verkehrsnachfragemodellierung und der Nutzen-Kosten-Analyse ermöglicht wird. Notwendig ist die Modellentwicklung und die damit verbundene Zusammenführung, da die derzeit praktizierte methodische Trennung zum einen nicht theoriekonform mit der Nutzen-Kosten-Analyse ist, zum anderen daraus fehlerhafte Ergebnisse im Rahmen der ökonomischen Gesamtbewertung einer Verkehrsinvestition resultieren können. Das entwickelte Modell liefert als Ergebnis einerseits die Verkehrsnachfrage für den Ohne- und Mitfall (ohne und mit zu bewertender Verkehrsinvestition), andererseits wird die Änderung der Konsumentenrente der Verkehrsteilnehmer ausgegeben, die unmittelbar in die Nutzen-Kosten-Analyse einfließt. Das zugrundegelegte Verkehrsnachfragemodell ist das EVA-Logit-Modell, das dem EVA-Grundmodell in Form eines Logit-Modells entspricht und damit mikroökonomisch interpretierbar und integrierbar ist. Die Nutzenänderung der Verkehrsteilnehmer wird durch das Integral des EVA-Logit-Modells bestimmt und mit Hilfe der in der Verkehrsnachfrage modellierten Bewertungspräferenzen der Verkehrsteilnehmer gegenüber den Reisekosten monetarisiert. Das Ergebnis stellt die konsistent bestimmte Änderung der Konsumentenrente dar. Die Funktionsfähigkeit und Verwendbarkeit des entwickelten Modells wird anhand einer Beispielanwendung getestet.
358

Routing in stochastic environments

Uyar, Emrah 17 November 2008 (has links)
In this thesis, we study two stochastic vehicle routing problems. In the first part, we investigate a routing problem where the distributor wants to construct a set of delivery routes each day to serve a set of geographically dispersed customers, but wants to send the same driver to the same set of customers as much as possible due to business requirements. The stochastic nature of customer demands and the existence of hard delivery time windows make this fixed routes problem much harder. We introduce a new recourse policy based on limited vehicle sharing and develop heuristic approaches for constructing fixed routes respecting the new policy for large real-life instances. Among the key contributions is the introduction of sampling-based techniques to handle the feasibility issues arising from hard delivery windows. An extensive computational study based on real-life data demonstrates the efficacy of the proposed fixed routing system and route construction techniques. In the second part, we investigate the new policy in an abstract setting to understand its properties. We characterize the optimal traditional fixed routes solution in terms of total expected cost for simple instances of the problem. Next we present a series of results for the new policy. For example, we show that operational feasibility of a set of fixed routes can be checked in polynomial time, but identifying the optimal use of fixed routes is NP-complete. In the final part, we focus on a dynamic and stochastic routing problem, which arises when there are service level agreements in place between a distributor and its customers. Specifically, the distributor has to serve customer orders within two days after the order is received, but has the flexibility to choose the actual delivery day. However, future customer orders are unknown and are revealed dynamically through time. We develop heuristic and optimal policies for simple instances of the problem that use the stochastic information about future orders. We empirically compare the performance of the various policies with the performance of policies that do not use future information and with an offline optimal policy which has perfect information about future orders.
359

Impact of the location of new schools on transportation infrastructure and finance

Wagner, James Bartley 19 February 2009 (has links)
Public school planning and land use planning have become increasingly separated fields over the last 35 years. This results in misaligned goals when school districts do not plan facilities that support a community's land use planning goals. The result is a disjointed growth pattern where new schools are built on the urban fringe and act as a magnet for new development that often goes against desired development patterns. Previous research on school locations and development patterns has focused on institutional barriers to cooperation and strategies to help local governments cooperate better with local land use planners. To date, there has been no significant research that attempts to quantify the relationship between school location and development patterns and the transportation infrastructure necessary to serve new development. This research shows that there is a relationship between school location and new development. Four counties in Georgia were selected as case studies and analyzed with a Geographic Information System (GIS) to determine the significance of the link between these activities. Counties were selected based on their character (urban, suburban, exurban, rural) and analyzed separately. An elementary school and high school were analyzed for each county. In addition, interviews with school facility planners were conducted to further define what institutional barriers prevent cooperation among local land use planners and school planners. It was found that there is a wide range of levels of cooperation between school planners and local planners. Some school districts had a formalized communication process with local planners, some had an ad-hoc communication process, and others had no process at all. Recommendations are made on ways to improve the cooperation between these two professional fields. This thesis also examines the link between education and transportation capital funding. Georgia lawmakers are struggling to determine what type of capital funding mechanism would be appropriate for new transportation projects, but these new projects may negatively impact educational funding, which is currently based on a sales tax.
360

The distribution and impact of roads and railroads on the river landscapes of the coterminous United States

Blanton, Paul, 1968- 09 1900 (has links)
xvi, 150 p. : ill. (some col.), maps (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Floodplain roads and railroads are common features in river landscapes, but their distribution and impacts have not been explicitly studied. This dissertation discusses the impacts of floodplain roads and railroads on channel and floodplain processes in river landscapes at the continental, regional, and local scales. At the continental scale, I documented the spatial patterns of roads and railroads in the floodplains of the continental United States and the regional variability of their potential impacts. Based on these results, I developed a conceptual model based on topography and the interaction of transportation and stream networks that suggests that the area of lateral disconnection caused by transportation infrastructure should be most extensive in mid-sized alluvial valleys in relatively rugged settings, such as those located in the western United States. I used pre-existing digital geologic, hydrologic, and transportation data with Geographic Information Systems software to map floodplain areas and lateral disconnection along the floodplains of two river systems in Washington State. I developed methods to quickly and inexpensively delineate potential or historic floodplain surfaces, to analyze lateral floodplain disconnection caused by different types of structure, and to rank floodplain reaches in terms of salmon habitat potential. Although all floodplains exhibited disconnection, the floodplain maps and habitat rankings helped identify opportunities for habitat preservation and restoration. At the local scale, I mapped and measured the impacts of lateral disconnection, showing that channel and riparian habitat was degraded in locations with floodplain transportation infrastructure confining the channel compared with similar nearby sites lacking such confinement. Railroad grades and road beds function as confining structures in the riparian zone, disrupting flood pulses and the exchange of water, sediment, and biota between channels and their floodplains and within the floodplain. Over longer time periods, these structures can also impede the natural meandering and migration of channels across their floodplains, disrupting the erosional and depositional processes that drive the high habitat and biological diversity characteristic of floodplains. My results show that human-caused disconnections need to be further incorporated into river science and management. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: W. Andrew Marcus, Chairperson, Geography; Daniel Gavin, Member, Geography; Patricia McDowell, Member, Geography; Joshua Roering, Outside Member, Geological Sciences

Page generated in 0.1015 seconds