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- Archer, Jeffery, 1961-
(author)
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Indicators for traffic safety assessment and prediction and their application in micro-simulation modelling : a study of urban and suburban intersections
- 2005
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Doctoral thesis (other academic/artistic)abstract
- In order to achieve sustainable long-term transport infrastructure development, there is a growing need for fast, reliable and effective methods to evaluate and predict the impact of traffic safety measures. Recognising this need, and the need for an active traffic safety approach, this thesis focuses on traffic safety assessment and prediction based on the use of safety indicators that measure the spatial and/or temporal proximity of safety critical events. The main advantage of such measures is that they occur more frequently than accidents, and therefore require relatively short periods of study to establish values that can later be used for comparison, or for accident prediction purposes. There are a number of more generally accepted safety indicators including: Time-to-Accident, Time-to-Collision, and Post-Encroachment Time. These are based on different underlying principles and measurement techniques, including both on-site subjective estimation, and objective photometric measures. A major part of the work presented in this thesis, concerns identifying the potential and limitations of the different safety indicators with regard to their validity and reliability, and practical use for safety assessment and prediction purposes. This is done in conjunction with field studies in the urban and suburban environment, at both signalised and unsignalised intersections. Results from these studies indicate that on-site observation methods provide useful quantitative and qualitative information relatively quickly and efficiently, provided that they are used correctly. On the other hand, the methods based on photometric measurement (video-analysis) proved arduous and time-consuming. Furthermore, there are questions regarding the abilities of the Time-to-Collision and Post-Encroachment Time safety indicators to adequately represent interaction severity, suggesting possible flaws in fundamental concepts related to construct validity. Importantly, results showed that the relationship between safety indicators and traffic accidents is complex and equivocal, where many different factors and processes can impose a significant influence on safety. This makes generalised predictive modelling a particularly difficult task for safety analysts. The potential of micro-simulation for traffic safety and performance estimation based on the use of safety indicators was investigated in the second part of this thesis. Microscopic traffic simulation has become increasingly popular among transport planners, due to the fact that it serves as a safe and flexible off-line test environment for the estimation of dynamic and complex traffic system effects. It is useful and cost-effective in relation to the evaluation of issues concerning roadway design, and technological systems that influence road-user behaviour and vehicle performance. For reasons related to modelling fidelity and data quality, simulation has seldom been used for traffic safety estimation. Simulation model development is however, undergoing rapid development and the area of ‘safety-simulation’ and is recognised as having a high potential in the field of transport planning and traffic engineering. As part of the work in this thesis, practical simulation experiments were carried out to investigate this potential, and identify limitations. Based on the data from one of the earlier studies, and knowledge regarding important safety-influencing factors and behavioural processes, one of the simulation experiments showed evidence to suggest that realistic safety critical events could be generated and measured using safety indicators in a simulation environment, without making unnecessary and unrealistic behavioural assumptions. Furthermore, a second application of this methodology revealed the safety potential of a rear-end incident-reduction function used in standard vehicle actuated signalling. While both of these simulation studies highlighted the potential of this type of approach, the need for more flexible and realistic models of interactive behavioural processes could be identified in addition to the general need for greater active research into the field of safety simulation.
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| 2. |
- Atterhög, Mikael, 1962-
(author)
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The effect of competition and ownership policies on the housing market
- 2005
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Doctoral thesis (other academic/artistic)abstract
- This dissertation consists of five studies presented in seven essays. The overall objectives are to investigate the extent and consequences of competition on the rental housing market as well as the importance of national government policies for the substitute good, i.e. owner-occupied housing. However, each essay also has specific objectives. Due to the characteristics of the housing market, one should not expect competition to be very fierce. The market characteristics are, for instance, capital-intensive, complicated and time-consuming construction processes as well as a limited supply of land in many areas. In fact, firms have a lot to gain from colluding and to avoid e.g. price wars. It is therefore theoretically more likely that housing companies will engage in “functional” or “strategic” competition such as the quality of housing services. Essay I and IV analyze the unique municipal housing market in Sweden where apartment rents are determined by negotiations between the local municipal company and the local Union of Tenants. A regression analysis is applied on data from 30 municipalities. There was a strong correlation between apartment rents at local municipal markets and the level of “external” competition (measured by the price level on the market for single-family owner occupied housing), but not with “internal” competition (measured by the market share of the municipal housing company) or the capital expenditure of the municipal housing company (presumed to reflect historical construction and renovation costs for the apartments). The dissertation also investigates the consequences on rents (essay II) and on the quality of housing services (essay III) from a local Swedish municipal housing company selling a substantial part of its apartment stock (15-40 percent) and thereby theoretically creating more competition. These essays use a quasi-experimental methodology whereby the development of the housing market in a privatization town is compared with the development in a very similar comparison town. It is found that privatization has lead to lower rents in the short- and medium-term in six out of seven privatization towns. The development of the quality of housing services was more related to the performance of each individual company and not a specific category of companies. In essay V, these results are merged and developed further. Essay VI presents a wide range of policies available for governments wishing to increase access to home ownership for low-income households and thereby increasing the pressure on rental housing companies to reduce rents. A systematic overview of policies is provided based on the four distinct time periods of a typical ‘housing career’ of a household; i.e. down payment accumulation stage, transaction stage, ownership stage and selling stage. It is found that many policies are required to meet the specific and differing needs of households for governments wishing to encourage home ownership. Essay VII describes that home ownership rates have increased in almost all industrialized countries during the period from World War II until mid-1990s. The essay analyses the implications of government policies and some other factors (e.g. national wealth, income distribution) on home ownership rates in 13 industrialized countries during the period 19702000. A fixed-effect model is applied on a panel data set. The most important result is that a statistically significant and positive correlation between government support and home ownership rates was found although this is only a preliminary conclusion since data was scarce.
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| 7. |
- Håkansson, Maria, 1966-
(author)
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Kompetens för hållbar utveckling : Professionella roller i kommunal planering.
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The number of political goals set, and decisions taken, in respect of environmental matters at both the international and the Swedish national, regional and municipal levels is constantly increasing. The overall goal in the Swedish context is to become a sustainable society. The municipalities are expected to hold a key role in this transition, specifically through their spatial planning and their responsibilities for environmental and health issues. The aim of this thesis is to increase our empirical understanding of the day-to-day planning practice and environmental work. One important assumption here is that changing conditions, for example in relation to changes in legislation or bureaucratic re-organisations, do not always have an impact on every-day professional practice. In focus are therefore the day-to-day work and the professional perspectives as the professionals themselves articulate them. Interaction between occupational groups, the role of occupational culture and perspective and the articulation of knowledge is highlighted. The methods used for empirical data gathering are qualitative interviews and focus group sessions. The theories applied concern mainly professions, organisational culture and planning theory. It is apparent in the studies that the professional groups often have simplified, stereotypical images of one another, even though each group without exception has respect for the other professional groups. However, there are difficulties in the translation between officials of knowledge and evaluation of facts of the different groups. There is often low understanding of the fact that other groups act based on their professional knowledge and experience. The thesis show that national regulations and legislation alone cannot guarantee that environmental management will be prioritised at the local level – a gap between national policy and local practice here is clearly demonstrated. It should however be noted that the level of environmental competence in the local public administration is adequate and increasing.
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| 8. |
- Kiamehr, Ramin, 1968-
(author)
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Precise Gravimetric Geoid Model for Iran Based on GRACE and SRTM Data and the Least-Squares Modification of Stokes’ Formula : with Some Geodynamic Interpretations
- 2006
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Doctoral thesis (other academic/artistic)abstract
- Iran is one of the most complicated areas in the world from the view of rough topography, tectonic activity, large lateral density and geoidal height variations. The computation of a regional gravimetric geoid model with high accuracy in mountainous regions, especially with sparse data, is a difficult task that needs a special attention to obtain reliable results which can meet the needs of the today geodetic community.In this research different heterogeneous data has been used, which includes gravity anomalies, the high-resolution SRTM Digital Elevation Model (DEM), recently published GRACE Global Geopotential Models (GGMs), geological maps and GPS/levelling data. The above data has been optimally combined through the least-squares modification of Stokes formula with additive corrections. Regarding the data evaluation and refinement, the cross-validation technique has been used for detection of outliers. Also, several GGMs and DEMs are evaluated with GPS/levelling data. The impact of utilizing a high resolution SRTM DEM to improve the accuracy of the geoid model has been studied. Also, a density variation model has been established, and its effect on the accuracy of the geoid was investigated. Thereafter a new height datum for Iran was established based on the corrective surface idea. Finally, it was found that there is a significant correlation between the lateral geoid slope and the tectonic activities in Iran.We show that our hybrid gravimetric geoid model IRG04 agrees considerably better with GPS/levelling than any of the other recent local geoid models in the area. Its RMS fit with GPS/levelling is 27 cm and 3.8 ppm in the absolute and relative senses, respectively. Moreover, the relative accuracy of the IRG04 geoid model is at least 4 times better than any of the previously published global and regional geoid models in the area. Also, the RMS fit of the combined surface model (IRG04C) versus independent precise GPS/levelling is almost 4 times better compared to the original gravimetric geoid model (IRG04). These achievements clearly show the effect of the new gravity database and the SRTM data for the regional geoid determination in Iran based on the least-squares modification of Stokes’ formula.
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- Larsen, Katarina, 1974-
(author)
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Innovation Processes and Environmental Planning : Science and Technology Policies in a Regional Context
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The understanding of environmental change and how it is influenced by innovation processes and advances in science and technology is multifaceted given the inherent uncertainty of the pace and direction of technology change, but also given the limits to anticipate future environmental effects of new technology. The doctoral thesis is organised in two parts. The covering essay constitutes the first part and is aimed at introducing the scope of the research; outlining theoretical perspectives and central concepts and positioning the research to other research studies. Reprints of the six papers included in the thesis comprise the second part of the thesis. The first aim of this doctoral thesis is to contribute to an increased understanding of the conditions for environmental policy and planning through innovation, science policy and technological change. Particular attention is paid to the institutional frameworks for policy processes, public-private interactive policy and strategic planning with futures studies. The second aim is to explore and analyse approaches applied for assessing the output, impact and structure of science in the area of strategic environmental research. This includes an examination of research assessment criteria and an analysis of knowledge networks in strategic environmental research, characterised by socio-economic expectations of generating innovations that benefit the environment through the industrial application of science. Four types of environmental planning are studied using a combined qualitative and quantitative research approach. These are corporate environmental planning, public environmental planning, strategic long-term planning, and strategic science planning targeting advances in science and technology to attain environmental objectives. The findings of the study show that institutional frameworks of science and technology policy affecting environmental planning are found in organisational forms, such as science parks, but also in institutions understood as values and norms of the science system. With an increased focus on assessment of research as well as future technology, the findings of the study also contributes by examining approaches applied for assessing the output, structure and impact of research, using bibliometrics and social network analysis in the area of strategic environmental research.
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| 10. |
- Martinson, Lina, 1975-
(author)
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Mutual benefit : Rethinking social inclusion
- 2005
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Doctoral thesis (other academic/artistic)abstract
- geography, where segregation and social exclusion of neighbourhoods and marginalised groups are mounting problems. Concurrently, globalisation and structural changes have altered the conditions for the national state and the public sector as well as for other actors. Previous efforts to decrease social inequalities have failed to achieve sufficient results. Today, promoting social inclusion and integration is a top priority on the political agenda and calls for innovative interventions. These changes in society have resulted in new constellations of collaboration, crosscutting sectors and borders in which various actors work towards collective goals. Many of the issues and subsequent responsibility that once belonged to the public sector are now handled through interplay between private and public actors in so-called governance arrangements. The thesis discusses if governance arrangements where new actors engage to promote social inclusion and integration can be more effective than traditional efforts. To reach satisfactory results, the relations between involved actors need to be solid and trustworthy, and the perspective of benefit must be long-term. In this respect, social capital is a central theory as it focuses on social relations between people, and emphasises networks, trust and reciprocal norms as important foundations for such relations. The aim of the thesis is to rethink strategies to promote social inclusion and integration by providing a theoretical discussion about value-creation. An assumption analyzed is that in situations where power and other resources are unevenly distributed, all parties involved can benefit by trustful cooperation. The ambition is to critically examine the concepts of governance and social capital, and to discuss their possibilities and shortcomings related to the value-creating processes. The usefulness and capacity of the theoretical framework is tested by analysing two unconventional approaches to promote social inclusion and societal integration, carried out by a public housing company in Malmö.
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