| 1. |
- Ahlberg, Joakim, 1966-
(författare)
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Multi-unit common value auctions : theory and experiments
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research on auctions that involve more than one identical item for sale was,almost non-existing in the 90’s, but has since then been getting increasing attention. External incentives for this research have come from the US spectrum, sales, the European 3G mobile-phone auctions, and Internet auctions. The policy relevance and the huge amount of money involved in many of them have helped the theory and experimental research advance. But in auctions where values are equal across bidders, common value auctions, that is, when the value depends on some outside parameter, equal to all bidders, the research is still embryonic.This thesis contributes to the topic with three studies. The first uses a Bayesian game to model a simple multi-unit common value auction, the task being to compare equilibrium strategies and the seller’s revenue from three auction formats; the discriminatory, the uniform and the Vickrey auction. The second study conducts an economic laboratory experiment on basis of the first study. The third study comprises an experiment on the multi-unit common value uniform auction and compares the dynamic and the static environments of this format.The most salient result in both experiments is that subjects overbid. They are victims of the winner’s curse and bid above the expected value, thus earning a negative profit. There is some learning, but most bidders continue to earn a negative profit also in later rounds. The competitive effect when participating in an auction seems to be stronger than the rationality concerns. In the first experiment, subjects in the Vickrey auction do somewhat better in small groups than subjects in the other auction types and, in the second experiment, subjects in the dynamic auction format perform much better than subjects in the static auction format; but still, they overbid.Due to this overbidding, the theoretical (but not the behavioral) prediction that the dynamic auction should render more revenue than the static fails inthe second experiment. Nonetheless, the higher revenue of the static auction comes at a cost; half of the auctions yield negative profits to the bidders, and the winner’s curse is more severely widespread in this format. Besides, only a minority of the bidders use the equilibrium bidding strategy.The bottom line is that the choice between the open and sealed-bid formats may be more important than the choice of price mechanism, especially in common value settings.
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| 2. |
- Ahmed, Abubeker W., 1981-
(författare)
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Mechanistic-Empirical Modelling of Flexible Pavement Performance : Verifications Using APT Measurements
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mechanistic-Empirical (M-E) pavement design procedures are composed of a reliable response model to estimate the state of stress in the pavement and distress models in order to predict the different types of pavement distresses due to the prevailing traffic and environmental conditions. One of the main objectives of this study was to develop a response model based on multilayer elastic theory (MLET) with improved computational performance by optimizing the time consuming parts of the MLET processes. A comprehensive comparison of the developed program with two widely used programs demonstrated excellent agreement and improved computational performance. Moreover, the program was extended to incorporate the viscoelastic behaviour of bituminous materials through elastic-viscoelastic correspondence principle. A procedure based on collocation of linear viscoelastic (LVE) solutions at selected key time durations was also proposed that improved the computational performance for LVE analysis of stationary and moving loads. A comparison of the LVE responses with measurements from accelerated pavement testing (APT) revealed a good agreement. Furthermore the developed response model was employed to evaluate permanent deformation models for bound and unbound granular materials (UGMs) using full scale APTs. The M-E Pavement Design Guide (MEPDG) model for UGMs and two relatively new models were evaluated to model the permanent deformation in UGMs. Moreover, for bound materials, the simplified form of the MEPDG model for bituminous bound layers was also evaluated. The measured and predicted permanent deformations were in general in good agreement, with only small discrepancies between the models. Finally, as heavy traffic loading is one of the main factors affecting the performance of flexible pavement, three types of characterizations for heavy traffic axle load spectrum for M-E analysis and design of pavement structures were evaluated. The study recommended an improved approach that enhanced the accuracy and computational performance.
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| 3. |
- Bagdadi, Omar
(författare)
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The development of methods for detection and assessment of safety critical events in car driving
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Improving our knowledge of drivers’ behaviour, especially in hazardous situations is a key to understanding why accidents occur and how to improve safety on our roads. Crash surrogate measures have proven to be very useful in traffic safety analysis. As a valid crash surrogate measure shares the same logical chain of events as actual crashes, studying those events increases the opportunities to analyze external circumstances as well as events and driver behaviour preceding the crash. A new definition of crash surrogate measures is proposed, i.e. safety critical braking events: Situations (including crashes) that require a sudden, evasive manoeuvre to avoid a crash or to correct for unsafe acts performed by the driver himself/herself or by other road users. This thesis develops a method for detecting Safety CRItical Braking Events (SCRIBE) and evaluates against other methods mostly used in large naturalistic driving studies. The evaluation shows promising results in the success rates of detecting safety critical events. Further, a Method for estimating the SEverity of safety Critical events (M-SEC) involving more than one road user, is developed and evaluated. The method combines a measure of closeness-to-collision, or safety margins, with a measure of possible consequences based on the speed and mass of the involved road users. Besides, a comparison is made with the Traffic Conflict Technique. Evaluation of the method shows that the estimated severity using M-SEC enables comparison of safety critical events involving different types of road users and is not limited to comparisons between similar types of events. In addition, the estimations when using M-SEC seem to reflect the seriousness of the safety critical events.
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| 4. |
- Bastian, Anne
(författare)
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Explaining Trends in Car Use
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many western countries have seen a plateau and subsequent decline in car travel during the early 21st century. What has generated particular interest and debate is the claim that the development cannot only be explained by changes in traditional explanatory factors such as GDP, fuel prices and land-use. Instead, it has been argued, the observed trends are indications of substantial changes in lifestyles, preferences and attitudes to car travel and thus, not just a temporary plateau but a true peak in car use.This thesis is a compilation of five papers, studying the issue on a national, international, regional and city scale through quantitative analysis of aggregate administrative data and individual travel survey data. It concludes that the aggregate development of car travel per capita can be explained fairly well with the traditional model variables GDP and fuel price. Furthermore, this thesis shows that spatial context and policy become increasingly important in car use trends: car use diverges over time between city, suburban and rural residents of Sweden and other European countries, while gender and to some extent income become less differentiating for car use.
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| 5. |
- Berg, Jessica
(författare)
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Everyday Mobility and Travel Activities during the first years of Retirement
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mobility is central to living an independent life, to participating in society, and to maintaining well-being in later life. The point of departure in this thesis is that retirement implies changes in time-space use and interruption in routines, which influence demands and preconditions for mobility in different ways. The aim of this thesis is to explore mobility strategies and changes in mobility upon retirement and how mobility develops during the first years of retirement. A further aim is to provide knowledge of the extent to which newly retired people maintain a desired mobility based on their needs and preconditions. The thesis is empirically based on travel diaries kept by newly retired people, and qualitative interviews with the same persons, and follow-up interviews three and a half years later. The results show that mobility is a way of forming a structure in the new everyday life as retirees by getting out of the house, either just for a walk or to do errands. Many patterns of everyday life remain the same upon retirement, but the informants also merge new responsibilities and seek new social arenas and activities. As a result, the importance of the car have not changed, but it is used for other reasons than before. After leaving paid work, new space-time constraints are created which influences demands for mobility. The study further shows that “third places” become important, especially among those who live alone, as they give an opportunity to being part of a social context and a reason for getting out of the house. The follow-up interviews revealed that declining health changes the preconditions for mobility. Daily walks had to be made shorter, and the car had to be used for most errands to where they previously could walk or cycle. However, mobility can also be maintained despite a serious illness and a long period of rehabilitation.
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| 6. |
- Berglund, Magnus, 1968-
(författare)
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Strategic Positioning of the Emerging Third-Party Logistics Providers
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The dissertation deals with the so-called Third-Party logistics Provider (TPLP) with the purpose of explaining strategic positions of the emerging TPLPs. The development of Third-Party Logistics (TPL) can be said to have occurred during the last 15 - 20 years and have created a new kind of service, i.e. the management and execution of logistics process. These services have created a new market and consequently a new type of service provideris emerging. These service providers predominantly originate from traditional offerings in the logistics area, e.g.transportation and warehousing activities. However, previous works on TPL have neglected the provider's situation especially by not explicitly recognizing the shifts from single activity services to comprehensive and coordinated multiple activity offerings and from a functional support orientation to a process approach.Strategic positioning is an established perspective on strategy, but the use varies considerably. In this dissertation strategic positioning is connected to how TPLPs create value for their clients which links positioning to skills or capabilities. Furthermore, the position is regarded as a result of the fit between activities, resources and strategic positioning. This theoretical frame of reference, based on strategic positioning and value creation for service organizations, is new in the literature on TPL. The general methodological approach of the study is alternation between empirical findings and theoretical analyses in a stepwise pattern. Since the organizations studied had not been theoretically analyzed before, empirical observations were instrumental in describing the novel phenomena. The empirical foundation of the dissertation is two studies executed during 1996-7 and 1998-9. The first study contains 21 Australian, European, and North-American TPLPs. The second study is based on 53 European TPL buyers. Both studies used a combination of questionnaires and interviews for collecting data of both quantitative and qualitative character. The empirical analysis is best described as a qualitative approach supported by statistical techniques whenever possible.The dissertation presents a comprehensive empirical description of the current status and anticipated change of both the TPLPs and their customers. The main contribution of this dissertation is however: tools for describing TPLPs, a model of the value system that connects providers and buyers of TPL, and a position model for TPLPs. The conclusions of this dissertation include that the TPL industry shows signs of strategic differentiation along the two strategic dimensions operational vs. conceptual focus and range of activities. Of these two the operational vs. conceptual focus is strong enough to promote as a position model, with the main positions standard services and solutions. A hypothesis is proposed that states that the strategic position of the TPLPs depends on which set of value creation modes they use, which results in differences in the required capabilities, skills and resources. In short the standard service providers should focus on operations whereas the solution ones needs exceptional conceptual skills in analyzing logistics requirements and developing solutions. The results should however be considered as hypotheses due to the research design used and thus need further empirical testing which is suggested as important future research.
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| 7. |
- Bhatti, Harrison John, 1979-
(författare)
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Sustainable Electromobility : A System Approach to Transformation of Transportation
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims to explore, analyze, and develop knowledge that leads to an understanding of identifying the key actors and their symbiotic relationships and dependencies in transforming the energy and transportation system from fossil-based to renewable and fossil fuel-powered vehicles to electric. The research was explorative and categorized into two studies. The Study – I focuses on the technological development that leads toward transforming from the old fossil-based analog electricity generation and distribution system to the new digitalized renewable system. This study further explores the impact of these disruptive technologies on the market and society, and the challenges hindering the implementation and adoption of the new energy system. Study – II focuses on developing new knowledge and understanding by integrating technological, political, societal, and economic aspects into one model and named it a 'multidimensional readiness index model.' This model can serve as an analytical tool and provide a broader perspective for exploring, analyzing, evaluating, and determining the countries' positions in transforming the transformation system. The model has been applied to eight countries, two from Asia (China and India) and Australia and five from Europe (Germany, Norway, Sweden, Slovenia, and the UK). The kappa synthesizes the exploration of the papers. Additionally, the system approach is applied to explore and understand the symbiotic relationship in the new ecosystem among the key actors and stakeholders and their significant role in transforming the transportation system from fossil-based to electric. The main conclusion is that the countries with a higher symbiotic relationship among the key actors achieved a higher level of readiness in transforming the transportation system. In contrast, other countries with a low symbiotic relationship among the key actors are slowly catching up or even far behind in transforming the transportation system towards electrification.
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| 8. |
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| 9. |
- Börjesson, Maria, 1974-
(författare)
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Issues in Urban Travel Demand Modelling : ICT Implications and Trip timing choice
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Travel demand forecasting is essential for many decisions, such as infrastructure investments and policy measures. Traditionally travel demand modelling has considered trip frequency, mode, destination and route choice. This thesis considers two other choice dimensions, hypothesised to have implications for travel demand forecasting. The first part investigates how the increased possibilities to overcome space that ICT (information and communication technology) provides, can be integrated in travel demand forecasting models. We find that possibilities of modelling substitution effects are limited, irrespective of data source and modelling approach. Telecommuting explains, however, a very small part of variation in work trip frequency. It is therefore not urgent to include effects from telecommuting in travel demand forecasting. The results indicate that telecommuting is a privilege for certain groups of employees, and we therefore expect that negative attitudes from management, job suitability and lack of equipment are important obstacles. We find also that company benefits can be obtained from telecommuting. No evidences that telecommuting gives rise to urban sprawl is, however, found. Hence, there is ground for promoting telecommuting from a societal, individual and company perspective.The second part develops a departure time choice model in a mixed logit framework. This model explains how travellers trade-off travel time, travel time variability, monetary and scheduling costs, when choosing departure time. We explicitly account for correlation in unobserved heterogeneity over repeated SP choices, which was fundamental for accurate estimation of the substitution pattern. Temporal constraints at destination are found to mainly restrict late arrival. Constraints at origin mainly restrict early departure. Sensitivity to travel time uncertainty depends on trip type and intended arrival time. Given appropriate input data and a calibrated dynamic assignment model, the model can be applied to forecast peak-spreading effects in congested networks. Combined stated preference (SP) and revealed preference (RP) data is used, which has provided an opportunity to compare observed and stated behaviour. Such analysis has previously not been carried out and indicates that there are systematic differences in RP and SP data.
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| 10. |
- Eek, Magnus
(författare)
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On Credibility Assessment in Aircraft System Simulation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aeronautical industry is becoming increasingly reliant on Modeling and Simulation (M&S) for use throughout all system development phases, for system verification, and end-user training. To justify and to utilize the full potential of today’s model-based approach, the development of efficient and industrially applicable methods for credibility assessment of M&S efforts is a key challenge.This work addresses methods facilitating credibility assessment of simulation models and simulator applications used in aircraft system development. For models of individual aircraft subsystems, an uncertainty aggregation method is proposed that facilitates early model validation through approximate uncertainty quantification. The central idea is to integrate information obtained during component level validation directly into the component equations, and to utilize this information in model level uncertainty quantification.In addition to methods intended for models of individual subsystems, this work also proposes a method and an associated tool for credibility assessment of large-scale simulator applications. As a complement to traditional document-centric approaches, static and dynamic credibility information is here presented to end-users directly during simulation. This implies a support for detecting test plan deficiencies, or that a simulator configuration is not a suitable platform for the execution of a particular test. The credibility assessment tool has been implemented and evaluated in two large-scale system simulators for the Saab Gripen fighter aircraft. The work presented herein also includes an industrially applicable workflow for development, validation, and export of simulation models.
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