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  • 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.
1

Performance measurement for highway winter maintenance operations

Qiu, Lin 01 January 2008 (has links)
Many highway maintenance agencies are facing an increased pressure to utilize their limited resources while still achieving the optimum winter highway maintenance outcome. Also there is a tendency to privatize maintenance operation, in order to improve the road user's satisfaction by bringing more competition to winter maintenance operations. Given this context the purpose of this research is to develop an effective performance measurement system that can evaluate how well agencies have conducted winter maintenance activities to meet the road user's expectations of safety and mobility. Though there have been performance measurement studies conducted in the winter maintenance area, few of them are comprehensive enough to evaluate winter maintenance outcomes, while at the same time taking storm severity, road system characteristics, and maintenance effort together into consideration. To address this deficiency, several particular challenges must be considered: first, how to evaluate the storm severity for individual storms; second, how to evaluate maintenance outcomes using a series of quantitative measures; and third, what are the appropriate targets that maintenance outcomes can be compared with, considering outcomes are sensitive to maintenance input, weather severity, road classifications, and traffic specifications. To address these questions: A storm severity index is developed; studies on effects of weather were quantitatively synthesized by meta-analysis; effects of weather and maintenance on road surface conditions are estimated by MLR; SEM (Structural Equation Modeling) is applied to estimate the direct and indirect effects of maintenance on mobility and Multiple Classification Analysis (MCA) was applied to estimate the contribution of winter maintenance to safety. The final result of this research is an applicable winter maintenance performance measurement system. It informs maintenance agencies where they excel at and where improvements are needed for the specified goals. Further, the developed road surface condition prediction model can be used as a predictive tool to allow agencies to conduct "what if" experiments that will lead to optimization of maintenance practice over time. The relative magnitudes of the effects of different maintenance methods on mobility and safety that is estimated by the models will enable agencies to assign priorities, and to compare maintenance outcomes based on the input resources.
2

Comparative Analysis of VANET and Vehicular Cloud Models with Advanced Communications Protocols

Sukhu, Jonathan Brandon January 2024 (has links)
Vehicular communication systems are integral for efficient highway operational management and for mitigating severe traffic congestion. While vehicular ad hoc networks (VANET) are reliable and provide avenues to minimal reliance on existing infrastructure, they can experience high communication overhead and network disruptions. Vehicular micro clouds (VMCs) provide a promising solution to overcome the challenges of VANET by reducing communication latency through cooperative and collaborative resource allocation and data offloading. This thesis offers a comparative performance analysis of freeway incident management and vehicle platooning, comparing VANET communications versus stationary and platoon-based dynamic VMCs. Specifically, it studies speed and lane-changing advisories in addition to freeway platooning. To further enhance the analysis, the performance of both communication architectures is evaluated using communication protocols of DSRC versus cellular technologies of C-V2X, 4G LTE, and 5G NR for latency, bandwidth, range, and deployment considerations. The system-level features, such as driving safety and vehicular mobility are measured to evaluate the efficacy of the communication systems under incident-induced traffic conditions. The study uses the AIMSUN microscopic traffic simulator to model and analyze the performance of the proposed systems. Key performance indicators include communication latency and packet loss ratio. In addition, the stationary and dynamic cloud systems show advantages in reducing travel time delay, even at high penetration rates of the connected vehicles, whilst reducing collision risks. On average, we observe improvements in travel time by 10% by implementing vehicular clouds over traditional ad-hoc networks. From a communications standpoint, the overall latency delay and packet loss are reduced by 7% and 11%, respectively, with the implementation of cloud models. The findings also delineate the benefits of dynamic cloud models, given their improved manoeuvrability, can maximize the computational capabilities of CVs, even at high market penetrations in large-scale freeway demands. The results suggest a shift towards more reliance on connected vehicular clouds to minimize the risks associated with message interference and system overload, whilst fostering advancements in intelligent freeway traffic management systems. / Thesis / Master of Applied Science (MASc)
3

Perceived cycling safety during Corona times - Results of a longitudinal study in Germany

Francke, Angela, Papendieck, Paul, Schaefer, Lisa-Marie, Anke, Juliane 28 December 2022 (has links)
With the beginning of the COVID-19 outbreak and the restrictions put in place to prevent an uncontrolled spread of the virus, the circumstances for daily activities changed. A remarkable shift in the modal split distribution was observed. Cycling was seen as a reliable and resilient option in pandemic times as it allowed social distancing and poses a low risk of contagion. There are detailed studies on the effect of the pandemic on cycling traffic all over the globe which used different data sources, like app data. counters or surveys [1] [2]. Apart from the citizens' behavioral responses to the corona pandemic, the municipalities also put up interventions that were meant to support a shift to cycling-based movements in cities. The question to discuss is what changes will be permanent and which changed circumstances, e.g. increased subjective safety, lead to a long-term change of mobility patterns. The changes in mobility during the COVID-19 pandemic bad different impacts on road traffic collisions and road deaths in different countries. While there was a reduction of both indicators in 32 out of 36 countries in April 2020 compared to April 2019, there was an increase in the other four countries [3]. Others also found a reduction of traffic fatalities in 23 out of 24 countries in 2020 compared to a baseline of the previous years (2017-2019), the only exception being Switzerland [4]. The subjective well-being has also changed differently for the different transport modes throughout the pandemic. For example, in April 2020, 9% of respondents said they would feel more comfortable or much more comfortable if they used or would use a bicycle compared to pre-pandemic times; in summer and autumn 2020, this figure was 11 %, in spring 2021, it was 13%. In autumn 2021, 15% of respondents said they would feel more comfortable or much more comfortable if they used or would use a bicycle than before the spread of the coronavirus [ 5]. [From: Introduction]
4

Urban Cycling and Automated Vehicles

Bruss, Lennart, Müller, Anja 03 January 2023 (has links)
Connected and automated vebicles (CA Vs) will shape traffic patterns in the future and greatly influence urban mobility. A particular challenge for CAVs is to anticipate the movements of other road users. This applies especially to micromobility vehicles (bicycles, smaU electric vehicles), whose traffic behaviour is difficult to predict and shaped from individual behaviour. The increasing coexistence of CAVs and other, conventionally driven modes of transport thus has a growing impact as well as multiple consequences for urban structures and public space. The following fundamental trends will shape the way people live together in cities in the coming years: 1. increasing share of CAVs and micromobility, 2. renaissance ofthe mixed and liveable city, 3. changes in mobility behaviour and the appreciation of public space ( especially due to climate change and the Covid 19-pandemic), as weil as 4. technical upgrading of infrastructure. These parallel developments will lead to both conflicts and opportunities for cities.[from Introduction]
5

Training älterer Radfahrerinnen und Radfahrer. Förderung von posturaler Kontrolle, Beweglichkeit und Fitness bei älteren Radfahrerinnen und Radfahrern – Einfluss auf Verkehrsmittelwahl und Verkehrssicherheit. Abschlussbericht.

Hagemeister, Carmen, Bunte, Heike 11 August 2017 (has links)
Das Fahrrad ist ein attraktives Verkehrsmittel für Menschen jeden Alters. Es ermöglicht Mo-bilität und damit gesellschaftliche Teilhabe bis ins hohe Alter, ist preiswert, und die regel-mäßige Bewegung verbessert die Gesundheit und macht Spaß. Da allerdings Radfahrerinnen und Radfahrer ab 60 Jahren besonders von schweren Unfallfolgen betroffen sind, ist bei ihnen die Verhütung von Unfällen wichtig. Typische Unfälle älterer Radfahrender hängen mit körperlichen Schwierigkeiten zusammen, die mit zunehmendem Alter häufiger werden. Die Beweglichkeit nimmt ab, was das Auf- und Absteigen erschwert und auch den Schulterblick beim Linksabbiegen. Etwa jeder sechste Unfall, aufgrund dessen ältere Radfahrer im Kran-kenhaus behandelt werden, ist dadurch entstanden, dass der Radfahrer beim Auf- oder Ab-steigen von der Pedale gerutscht ist. Weitere typische Unfallursachen sind Schwierigkeiten mit der Oberfläche (Schlaglöcher, Bordsteinkanten u.ä.) aufgrund abnehmender Koordinati-onsfähigkeit und fehlendes Umschauen beim Linksabbiegen. Durch die körperlichen Verän-derungen wird das Radfahren im Alter nicht nur gefährlicher, sondern auch mühsamer und damit auch weniger attraktiv als in jüngeren Jahren. Kraft und Kondition nehmen ab, wodurch lange Touren und Anstiege weniger attraktiv sind. In Zusammenarbeit mit der Universität Leipzig wurde ein motorisches Training für ältere Radfahrerinnen und Radfahrer entwickelt, das die motorischen Schwierigkeiten beseitigen sollte. Dieses Training wurde in 14 mittleren und kleinen Städten in Sachsen und Sachsen-Anhalt experimentell geprüft. An dem Training nahmen ein halbes Jahr lang 147 Radfahrende ab 60 Jahren teil, die in 7 Orten oder deren Umgebung lebten. Sie wurden mit 167 un-trainierten Radfahrenden ab 60 Jahren verglichen, die in oder bei 7 anderen Orten lebten. Es fanden drei Testungen und Befragungen statt, vor dem Training, direkt danach und vier Mo-nate nach Abschluss des Trainings. Die Projektpartnerinnen der Technischen Universität Dresden waren zuständig für die Prüfung der Effekte hinsichtlich Intensität der Radnutzung, geschilderter körperlicher Beschwerden und darauf resultierender Beeinträchtigungen im Straßenverkehr, erlebte Schwierigkeiten beim Radfahren und die Leistung in einem Fahrradparcours. Es konnte kein Effekt des Trainings auf diese Maße gezeigt werden. Schon bei der ersten Testung berichteten die Teilnehmenden insgesamt keine bis wenig körperliche Beschwerden und nur geringe Schwierigkeiten beim Radfahren, so dass hier von einem Bodeneffekt auszugehen ist. Ähnliches galt für die Fahrleistung. Viele Teilnehmende wurden über Sportvereine rekrutiert, um nicht nur extrem aktive Radfahrende für die Untersuchung zu gewinnen. Allerdings zeigte sich, dass die Teilnehmenden das Fahrrad auch schon vorher für viele Wege nutzten. Ent-sprechend erhöhte das Training die Fahrleistung nicht. Auch die Leistung im Fahrrad-Parcours wurde durch das Training nicht verbessert, obwohl hier so viele Fehler gemacht wurden, dass Spielraum für eine Verbesserung gewesen wäre. Die Befragten wurden nach Alleinunfällen und Zusammenstößen mit anderen Verkehrsteil-nehmenden nach dem 59. Geburtstag gefragt; 81% dieser Unfälle waren Alleinunfälle. Das Fahrrad hatte viele Teilnehmende über ihr gesamtes Leben begleitet, wie die Mobilitätsbio-grafien zeigten. Die Wegetagebücher zeigten, dass die Gewohnheit den stärksten Einfluss bei der Verkehrsmittelwahl hatte. Das Rad, das Zu-Fuß-Gehen und das Auto waren für die Teilnehmenden sehr wichtig, öffentliche Verkehrsmittel im Nah- und Fernverkehr kaum. Die subjektive Bedeutung des Radfahrens zeigte sich in den Faktoren Praktischer Nutzen, Le-bensqualität, Kontakte/Aktivitäten und einem Faktor, der auch auch positive Folgen des Auf-hörens (Fahrrad nicht mehr reparieren müssen) beschreibt. Stärkere Auswirkungen des Auf-hörens erwarten Personen, die das Rad mehr nutzen und seltener Auto fahren. / Cycling is an attractive mode of transport for persons of any age. It offers mobility and there-fore participation in society up to old age and is inexpensive. Regular physical activity improves health and is fun. On the other hand, cyclists aged 60 and older tend to suffer severe consequences when they are involved in accidents. For this reason accident prevention is especially important for this group. Typical accidents involving older cyclists are related to physical difficulties which are more frequent in older persons. About one in six accidents requiring physical treatment in hospital is due to slipping from the foot pedal while mounting a bike or dismounting from it. Further typical causes of accidents are difficulties with the surface (potholes, curbs, etc.) and not turning round before an offside turn. Physical changes make cycling not only more dangerous for older persons but also more strenuous and for this reason also less attractive. Strength and fitness decrease, making longer cycling tours and hills less attractive. Physical flexibility decreases, making mounting and dismounting and turning round before an offside turn more difficult. As coordination decreases, dealing with bad surfaces becomes harder. In cooperation with Leipzig University, a motor training concept for older cyclists was devel-oped. The aim of this training program was to reduce the motor difficulties of older cyclists. The training program was tested in an experimental design in 14 medium and small cities in Saxony and Saxony-Anhalt. 147 cyclists aged 60 or older participated in a half-year training program. These subjects lived in or close to seven cities. They were compared to 167 cyclists aged 60 and older who lived in or close to 7 other cities. The participants took tests and answered questionnaires three times, before the training program, immediately after the training program and four months after the training program. The project partners from Technische Universität Dresden were responsible for testing the effects of the training on intensity of bike use, reported physical problems and their conse-quences in traffic, perceived difficulties in traffic situations and performance in a cycling course. No effect of the training on these measures could be shown. Already in the first test period the participants reported too few physical problems and resulting difficulties in traffic, and only few problems in traffic situations. Here a ceiling effect was found. A similar result was found for cycled distance. Many participants were recruited via sports clubs in order to ensure that not all participants were highly active cyclists. But the first survey shows that the participants already used their bike for many trips before the training program. For this reason the training program did not increase cycled distance. The training program did not improve performance in the cycling course, although so many mistakes were made that there was certainly plenty of scope for improvement. The participants were questioned about single bike crashes and crashes with other road users after their 59th birthday; 81 per cent of these crashes were single bike crashes. For many participants, their bike had been an accompanying feature during their whole life, as their mobility biographies showed. The trip diaries showed that habits had the most important influence on choice of transport mode. Cycling, walking and driving were very important for the participants, public transport was relatively unimportant for short as well as for long dis-tances. The subjective importance of cycling was evident in terms of the factors practical benefit, quality of life, contacts/activity and a factor which comprised positive consequences of giving up cycling as well (no more bike repair). Persons who use their bike more and drive less expect more severe consequences if they stop bicycling.

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