Fundamental differences exist in soil types formed under temperate and tropical climatic conditions. Consequently, their use for road pavement design will require different approaches and standards. The absence of a systematic approach in addressing tropical pavement design requirements and the use of temperate design standards for tropical countries has led to early failure of road pavements in Ghana and other tropical countries. However, few studies have been carried out on developing standards based on field studies to determine key design parameters to address challenges of tropical pavement design. The aim of this research is to evolve a rational approach using mechanistic-empirical principles to design pavements for tropical laterite soils. The main objectives were therefore to determine the key pavement design parameters for Ghana through empirical studies as well as carry out technical and economic analysis to establish optimum designs for the various climatic zones of Ghana.

Soil stabilisation is one of the most common techniques used to mitigate the undesirable properties of soft soils such as low compressive strength and high compressibility. Cement is the most commonly used binder for soil improvement applications in the UK and worldwide due to its high strength performance. However, its manufacture is energy intensive and expensive, contributing approximately 7% of global carbon dioxide (CO2) emissions. Therefore, the search for alternative raw materials, such as waste and by-products, is becoming critical in order to develop cost effective and more environmentally friendly binders to replace cement and reduce its negative environmental impact. Blended waste material fly ashes have been identified as promising alternatives to traditional binders (cement CEM-I) in different construction industries including ground improvement. The reuse of waste material fly ashes such as waste paper sludge ash (WPSA), palm oil fuel ash (POFA) and rice husk ash (RHA) has many advantages, specifically in terms of eliminating the cost of their transportation and eventual landfill, their continuous supply and the negligible, or zero, cost of production. This research project details the process of the development of a new cementitious binder, produced by blending cement-free WPSA, POFA and RHA under physico-chemical activation using flue gas desulphurisation (FGD) gypsum, for use in soft soil stabilisation. The effects of different binders produced from unary (WPSA), binary (WPSA and POFA) and ternary (WPSA, POFA and RHA) blended mixtures, along with ground and FGD gypsum activated ternary mixtures, on the geotechnical properties of soft soils, were extensively investigated. Comparisons of Atterberg limits, strength (unconfined compressive strength (UCS)), compressibility characteristics and durability (wetting-drying cycles effect) of untreated soil and soil stabilised with the optimum unary, binary, ternary and activated ternary mixtures and a reference cement treated soil, have been carried out. An investigation of the microstructural and mineralogical composition of the newly developed binder, in comparison to those of the reference cement, was also carried out using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) imaging and energy dispersive X-ray (EDX) spectroscopy analysis. The results indicate that the soil stabilised with the ternary mixture activated by FGD gypsum (T+FGD), had the greatest compressive strength, compressibility and durability improvement; the performance of the newly developed cementitious binder was comparable to that of the reference cement. This binder comprises 8% WPSA + 2% POFA + 2% RHA activated with 5% of FGD, by the total mass of binder. The addition of FGD gypsum has been observed to enhance the pozzolanic reaction, leading to improved geotechnical properties; mainly UCS which increased over time of curing and exceeded that for the soil treated with reference cement, after 180 days. The results obtained from XRD analysis, SEM testing and EDX analysis revealed the formation of hydrated cementitious products represented by calcium silicate hydrates (C-S-H), Portlandite (CH) and ettringite. The formation of these hydrates reveals the developments gained in the geotechnical properties of the treated soil. A solid, coherent and compacted soil structure was achieved after using T+FGD, as confirmed by the formation of C-S-H, CH and ettringite. Therefore, a new, Cost effect, eco-friendly and sustainable cementitious binder has been successfully developed and can be used with confidence for soft soil stabilisation, as a 100% replacement of conventional cement.

Society has gripped the concept of road transport and has utilised it for social, personal and economic gain. Amidst the apparent benefits, a number of concerns exist around the dangers, congestion, and monetary loss associated with vehicular transport. To counteract this, the introduction of driverless vehicles is being discussed by manufacturers and the Government. Whilst there are a number of apparent benefits, there is an overwhelming need to consider public perception and acceptance of autonomous vehicles. This research study therefore investigates the aforementioned, analysing and presenting the major issues and concerns related to their uptake. An interview and focus group based approach was adopted for this research, using the Charmaz (2006) constructivist grounded theory methodology. Interviews were conducted with a range of stakeholders and the results of the study detailed that the environment the vehicle and user operate in presents associated issues influencing perceptions, and that technology acceptance is strongly influenced by levels of Motivation in Intention, Acceptance/Usage and Control. Furthermore, acceptance is perceived differently by various stakeholder groups, each with their individual concerns and speculations. The discussion of the study considers the gathered perception to ascertain how best to introduce autonomous vehicles to the public market, highlighting and satisfying the current implications of doing so. This study highlights the need for further research in this discipline, based on the identification of many knowledge gaps. Further work is discussed and recommended in order to combat the limitations and opportunities identified within this thesis.

Even though the practical experience of using coarse unbound granular materials is extensive, detailed knowledge on the mechanical and hydraulic behavior is to a large extent lacking. Regarding influence of water on mechanical properties, this is even more pronounced. The main objective of this work was to investigate the influence of water on behavior and properties of coarse granular materials. The study comprises measurements of resilient properties, soil-water characteristic curve and influence of water content on dielectric properties measured by the use of time domain reflectometry (TDR). The work described herein comprised two test series in terms of materials: firstly, a series where the grading was changed and secondly, a series where the influence of increased contents of free mica was studied. To measure resilient response, triaxial testing, using sample size of 500 mm diameter and 1000 mm height, was performed mainly using constant confining pressures. Tests were performed at incrementally varying water contents up to almost full saturation. Dielectric response and matric suction of compacted specimens were measured in a steel box at varying water content. Results from the first series indicated that the influence of water content on resilient properties depends on the material grading. The coarsest grading, containing least fines, experienced only a small reduction when brought close to saturation. Specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared as water content increased, the specimens became more dilative. From the second series, generally, resilient modulus decreased with increased mica content and furthermore, elevated water contents caused reduction in stiffness. However, in relative terms, the reduction in resilient modulus caused by water decreased with increased mica content. The soil-water characteristic curves are influenced by grading coefficient and mica content; retentive capacity increases with decreased grading coefficient and increases with increased amount of mica. Volumetric water content as a function of apparent relative permittivity was fitted using a third-degree polynomial. Although, determined relationships deviated from Topp's (1980) relationship. Detailed information on the work is given in five enclosed papers. / QC 20100705

Highway Authorities in the United Kingdom have jurisdiction to control, maintain and improve the local highway network, and the Road Traffic Act 1988 places a duty on such authorities to take preventative measures to reduce road casualties. As such, engineers working for the Highway Authority are on the ‘front-line,’ and are required to deal directly with lay concerns relating to road safety. This study investigates the nature and characteristics of how local road safety issues are raised and how engineers respond to such issues in a local authority setting. A grounded theory methodology was applied in the collection and analysis of this data, and in the generation of subsequent emergent themes. Datasets were established containing textual data from correspondence between the lay public and the authority, and from local press reporting. This was augmented by 47 semi-structured interviews with engineers. The analysis demonstrates that road safety issues and their construction, form a distinct genre. There are certain characteristic structural elements and argumentative approaches, which are oft repeated, in lay formulations of road safety. Road safety issues are played out in a contested field, although engineers may have, in theory, the ‘expertise’ that grants them authority to assess, diagnose and implement mitigation measures; in practice they have little autonomy or control. Regulatory restrictions, political interference, resource impoverishment and a volatile public, severely limit engineers’ independence and discretion. In dealing with the exigencies and pressures of day-to-day front-line public service, engineers deploy certain strategies for ‘managing’ the public. These pragmatic strategies are examined in order to establish how engineers can best effect practical action, in the face of competing and often conflicting demands. In examining the rhetorical organisation of lay argumentative strategies, a ‘popular epidemiology’ of road safety is recreated. This term, borrowed from Brown (1992), encapsulates a folk philosophy with respect to accident causation and the measures that are considered necessary or appropriate to ameliorate/eliminate identified issues. It is suggested that in vivo formulations of road safety issues, such as the ‘accident waiting to happen’ are founded on vague premises, and constitute a category mistake. Projections from phenomenally troubling, yet largely unsubstantiable events, to those with profound material consequences, are neither necessary nor certain. In making decisions on substantial capital investments, engineers, by necessity, are required to assess competing sites on a more epistemically secure metric, namely the police road casualty record.

As is the case for most of the Departments of Transportation in the U.S., the Texas Department of Transportation has been experiencing fluctuations of budget for maintaining and preserving its highway infrastructure over the recent years. If the maintenance budget shortfall lasts for an extended period of time, the condition of the highway network would be harmed directly or indirectly since some maintenance work would be deferred or cancelled. Thus, in order to control and minimize the risk caused by maintenance budget reductions, it is important for highway agencies to adjust their maintenance and rehabilitation policies to accommodate budget fluctuations. This thesis presents a methodological framework that helps highway agencies quantify the risks to highway networks, and revise the highway routine maintenance work plans to minimize the impact of budget fluctuations. The proposed methodology aims to assist highway agencies in prioritizing and selecting maintenance functions according to the risk of not performing a specific maintenance activity. Also, this methodology considers the subjective nature of decision makers’ assessments, allowing different levels of confidence and different attitudes toward risk to be captured as the uncertainty and imprecision involved in the decision making process. In the case study, the proposed methodology is tested with a set of data obtained from the Texas Department of Transportation. The result is compared with the outcome obtained from the crisp Analytical Hierarchy Process using the same set of data. The outcomes from the two methodologies are very close, validating the effectiveness of prioritizing highway maintenance functions using Multi-Attribute Analysis with Fuzzy Pairwise Comparison. / text

A practical and reliable alternative or supplement to injury accident data is necessary to diagnose dangerous sites and evaluate remedial measures because available accident data is scarce, is lacking in detail about the events preceding the accident and it takes a long time to accumulate statistically reliable data. The most favoured alternative is the Traffic Conflicts Technique which satisfies most of the requirements of a supplementary measure, but has so far only been successfully validated for rural dual carriageway intersections (Spicer, 1973). To establish the technique it is necessary a) to ensure that the subjective judgements on which it is based are reliable, b) to develop the best methods of recording conflicts, and of training and selecting observers, and then c) to test the validity of the best available technique. The main part of this thesis reports three studies aimed at each one of these issues. In the first study intra observer reliability tested on filmed material varied between rs = 0.30 and 0.91 (0.65 overall for N = 42), but poor observers could be identified. By selecting the best observers an overall reliability figure of up to 0.88 could be obtained. Reliable observers remained reliable or even improved slightly on the second testing. These reliable observers also showed good agreement with expert judges who had viewed the film many times, and by selection a correlation with the criterion value of up to 0.83 could be obtained. In the second study a new recording method was developed, incorporating factors that experienced observers used to differentiate the grades of severity currently in use. This helped observers by defining the criteria for detection and grading of a conflict more objectively. This increased the overall intra observer reliability from 0.73 to 0.80, and agreement with the criterion values from 0.66 to 0.76. Transfer from laboratory to field led to a drop in the numbers of conflicts reported. From these studies and a survey of the requirements of local authority accident investigation units, a manual and training package was developed giving guidance on training and selecting observers for the purpose of obtaining reliable conflict data, such as that required for validating the technique. In the third study this package was validated in a study of a sample of eight urban T-junctions. Again the best observers were selected and found to have an overall reliability of 0.88. It was found that, when rear end conflicts were excluded (on the grounds that they led to so few reported injury accidents while occurring in large numbers), there was a high correlation between accidents per vehicle and conflicts per vehicle (rs = 0.79, p<0.025), accounting for 62% of the variance. This compares very favourably with the maximum possible percentage (77%) which could be expected given the relaibility (rs = 0.88) of the observers. Although a validity correlation of 0.79 is very satisfactory and the method of obtaining the data is reasonably economical, an attempt was made to find a still more economical alternative to accident statistics. The most obvious of these are subjective judgements or a combination of these with traffic flow. Traffic flow data for different manoeuvres at each of the eight T-junction sites were obtained and various groups of people were asked to judge the subjective risk of these sites from scale maps and photographs or directly on-site. Judgements from maps and photographs tended to be negatively correlated with accidents. The best subjective estimate (driving instructors judging on-site) correlated 0.44. An attempt to improve on these by combining the traffic flows and judged risk of the different manoeuvres at each site failed to produce a higher correlation. None of these correlations were significant, but the failure of any one of several different corrrelations to be higher than 0.46 suggests very strongly that these simpler methods are very unlikely to have the validity of the full conflicts technique. However, the present study has validated the Traffic Conflicts Technique only for urban T-junctions (the commonest of all accident sites). It could, therefore, only be used for evaluating the effects of small changes in the layout of such junctions. It could be used to evaluate more radical changes eg. T-junction converted to a mini roundabout, provided the conflict to accident ratios of the different layouts were known. In this study the conflict to accident ratio was 125:1 for vehicles turning right out of the minor road. For the T-junctions as a whole it was 275:1 while Older and Spicer(1976) found a ratio of 2000:1 for rural dual carriageway intersections. By obtaining more information of this kind, the utility of the Traffic Conflicts Technique could be greatly extended.

Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 157-163). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 106-110). Also available in electronic format on the Internet.

Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Yassir Abdelrazig, Florida State University, College of Engineering, Dept. of Civil and Environmental Engineering. Title and description from dissertation home page (viewed June 7, 2005). Document formatted into pages; contains x, 181 pages. Includes bibliographical references.