Roads constructed on expansive clays may be adversely affected by the behaviour of the clay. Expansive clays suffer volume change due to changes in moisture content which causes heaving, cracking and the break up of the road pavement. Stabilisation of these types of soil is necessary to suppress swelling and increase the strength of the soil and thus partially decrease the thickness of road pavement layers. The use of by-product materials for stabilisation has environmental and economic benefits. Ground granulated blastfurnace slag (GGBS), a by-product material in Egypt, and lime are used in the current work to stabilise samples of a clay soil similar to a typical Egyptian clay soil. This test soil comprises 80% River Aire soil and 20% calcium montmorillonite. The main objectives of this research were to investigate the effect of GGBS, with and without lime, on the engineering behaviour (plasticity characteristics, compaction, unconfined compressive strength (UCS) and swelling potential) of the test soil and to identify the reaction products of the stabilised materials to determine the mechanisms by which changes in engineering properties are obtained. In order to achieve these objectives, extensive laboratory investigations were carried out. Various mixes (up to 10% GGBS by dry weight of the test soil and up to 30% replacement by hydrated lime) were prepared and cured under two representative conditions {20°C with 90-100% relative humidity (CCI) and 35° C with 50-60% relative humidity (CC2)} for up to 12 months. Compaction and plasticity were measured soon after mixing, the swelling potential and UCS were measured after longer curing periods. Four analytical techniques {X ray diffraction, scanning electron microscopy, differential thermal analysis and nuclear magnetic resonance (NMR)} were used to identify the reaction products of the clay fraction of the test soil mixed with various amount of GGBS and lime. This pure clay test soil was used to ease identification of the reaction products. The investigations showed that generally the engineering properties (UCS, swelling, plasticity) improved with the addition of GGBS and with increasing curing period and temperature. The addition of lime resulted in a dramatic improvement within the test ranges covered in the programme. The maximum dry density, MDD, decreased and the optimum moisture content, OMC, increased with increasing GGBS and lime content. The major changes in the UCS and swelling behaviour are due to the formation of new cementitious materials. The analytical investigation confirmed two major reactions when GGBS and lime were added to the pure clay soil, hydration of GGBS activated by lime to produce calcium aluminosilicate hydrate gel (C-A-S-H) and hydrotalcite type phase, and the clay-lime reaction to produce calcium silicate hydrate (C-S-H), (C-A-H) and (C-A-S-H). The NMR test results revealed that the aluminosilicate chain length (EL), the aluminium: silicate (Al/Si) ratio and the amount of Si in the formed C-S-H significantly increased with an increase in the curing temperature and period, which indicates a more stable and well crystalline C-S-H. The results indicate that the use of GGBS alone, or preferably with lime, could have a significant effect on the behaviour of potentially swelling clays. Recommendations for further studies include a study of the effect of cyclic loading on the test soil. Also, site trials should be carried out to assess the suitability of using these materials in the field.

No description available.

The risk analysis process involving information acquisition, modeling, analysis, and decision steps result in system design improvement. To allow an accurate and active system risk assessment in road transportation, this study identifies the contributing factors in reliability of road transportation systems and develops the systematic and stochastic methodologies and mathematical models. The developed models and methodologies aim to assess the reliability and risk of drivers interacting with the today’s typical vehicles equipped with Advanced Drivers Assistance System (ADAS) and Passive Safety Systems (PSS) with any degree of complexity and availability of such systems. The research further examines and addresses the specific needs of such vulnerable users and perhaps risk to others on roads including older drivers, younger drivers and pedestrians. The research presents the conditions monitoring concepts as in-vehicle tools for live assessment of risk state of drivers built on the methodologies and models developed in the studies. The necessity for availability of good data and specific databases for purpose of risk assessment in road transportation is then highlighted and stressed. The complete procedure for accident investigation and data collection is developed and presented in the research and a conceptual model for a typical human centered reliability databases in road transportation is also developed. The research is novel and innovative and expected to pave the way for improvement and development of new risk mitigating systems and better assessment and monitoring of the safety of users on roads and with the capability of information sharing resulting in saving many lives worldwide.

Road pricing has emerged as an effective means of managing road traffic demand while simultaneously raising additional revenues to transportation agencies. Research on the factors that govern travel decisions has shown that user preferences may be a function of the demographic characteristics of the individuals and the perceived trip attributes. However, it is not clear what are the actual trip attributes considered in the travel decision- making process, how these attributes are perceived by travelers, and how the set of trip attributes change as a function of the time of the day or from day to day. In this study, operational Intelligent Transportation Systems (ITS) archives are mined and the aggregated preferences for a priced system are extracted at a fine time aggregation level for an extended number of days. The resulting information is related to corresponding time-varying trip attributes such as travel time, travel time reliability, charged toll, and other parameters. The time-varying user preferences and trip attributes are linked together by means of a binary choice model (Logit) with a linear utility function on trip attributes. The trip attributes weights in the utility function are then dynamically estimated for each time of day by means of an adaptive, limited-memory discrete Kalman filter (ALMF). The relationship between traveler choices and travel time is assessed using different rules to capture the logic that best represents the traveler perception and the effect of the real-time information on the observed preferences. The impact of travel time reliability on traveler choices is investigated considering its multiple definitions. It can be concluded based on the results that using the ALMF algorithm allows a robust estimation of time-varying weights in the utility function at fine time aggregation levels. The high correlations among the trip attributes severely constrain the simultaneous estimation of their weights in the utility function. Despite the data limitations, it is found that, the ALMF algorithm can provide stable estimates of the choice parameters for some periods of the day. Finally, it is found that the daily variation of the user sensitivities for different periods of the day resembles a well-defined normal distribution.

Africa’s conservation areas have vast road networks as a result of motorized vehicle game viewing. In conservation areas these roads provide increased accessibility to previously inaccessible areas, often with negative ecological impacts, such as wildlife fatalities and decreased habitat quality and connectivity. Additionally, tar roads often have a greater negative effect on mammal species than dirt roads, altering their spatial distribution and behaviour to a greater extent. The Kruger National Park, South Africa, has 2294 km of public roads within the park, of which 850 km is tarred – carrying a higher traffic density than dirt roads – and 1444 km is dirt. The aim of this study was to compare the ecological impacts of tar and dirt roads on medium to large mammal species in the Kruger National Park, hypothesizing that the tar roads within the park have greater negative impacts on the park’s mammal species. I focused on three response variables: 1. observation likelihoods; 2. species group sizes and 3. distances to the road, comparing tar to dirt roads. Sampling was done at 1 km intervals, for 430 km of tar and 430 km of dirt roads, in savanna vegetation during the Austral winter of 2017 and 2019. In total 476 sampling points were on tar roads (401 systematic and 75 ad hoc) and 451 on dirt roads (369 systematic and 82 ad hoc). At each sampling point, all observed medium to large mammals, their group size, distance of the closest individual to the road, GPS coordinates, traffic volume and percentage cloud cover were recorded. Chi-square analyses were used to identify associations between species presence and road type. To determine the relationship between group size and road type, as well as the observed distance from the road and road type, Generalised Linear Models (GLMs) were used. The results refute the hypothesis of increased ecological impacts associated with tar roads, as the majority of the commonly occurring mammal species were not disproportionately associated with a specific road type. My results indicated that, as a tourist, one has an equal likelihood of observing the majority of the common mammal species from either road type. The results suggest that the increased traffic intensity of tar roads does not decrease one’s chances of viewing game, as hypothesized. The commonly occurring species were also observed at similar distances from both road types, and all were observed on the road, suggesting a limited barrier effect, if any. Previous studies on the impacts of road type on mammals both support and contradict my results. Elephant (Loxodonta africana) was the only species that was associated with a road type, although the complete opposite was found to what was hypothesized. Elephant occurred more often alongside tar roads (albeit only in the north of the park) than dirt roads, in larger groups next to tar roads and closer to tar roads. Potential reasons that are discussed are higher quality forage, plant species richness, group vigilance and predator avoidance. My results can have an influence on park management decisions and communication with tourists. Tourists can be informed that they do not need to make use of dirt roads, which are often less accessible, to view game. In terms of road management, my results suggest that the temporary closure of dirt roads for rehabilitation should not affect game viewing. It is, however, suggested that further research is needed to compare the influence of public to private road areas on animal ecology within the Kruger National Park, as well as to compare the influence of road areas to completely natural areas. / Mini Dissertation (MSc (Environmental Ecology))--University of Pretoria, 2020. / Thuthuka programme - National Research Foundation (NRF) of South Africa (Grant no. 94103). / Zoology and Entomology / MSc (Environmental Ecology) / Restricted

Gypcrete occurs in the western arid and semi-arid regions of South Africa and Namibia. These soils exhibit a complex nature and abnormal behaviour due to their gypsum content and as such they have become more prevalent in research. As these soils are finding more use in industry, a keen understanding of their properties and behaviour is required. Powdery and indurated gyprete samples collected from the Northern Cape (Geelvloer) and Western Cape (Rooiberg and R355) Provinces, are subjected to a series of standard test protocols for road construction materials and then compared to similar studies done on gypcrete both in South Africa and abroad, where gypcrete is researched more extensively and used successfully. The samples collected were dried at 40 °C to prevent phase transitions that will affect the properties of the material. The strength of powdery gypcrete is sensitive to density changes; therefore achieving a high density during compaction is imperative, while the strength of more indurated samples remains unaffected by density. The soaking period before the CBR is also deemed unsuitable for gypcrete as four days results in an overestimation of strength. It is apparent that the properties of gypcrete are affected by several factors, including the formation conditions, type of gypsum, and amount of gypsum, particle size distribution, the size of gypsum particles relative to other particles in the soil and the presence of other salts, all of which affects gypcrete differently making it difficult to form clear trends. The samples are also subject to wetting and drying cycles at 40 °C and 60 °C before the CBR values are determined again, to assess the variation in strength due to mineral alteration. An increase is seen for all samples dried at the higher temperature. This leads to the notion that gypcrete possesses self-stabilising properties, where temperatures in hot areas could dehydrate the gypsum, which will then readily re-absorb atmospheric moisture, leading to the formation of cementing between particles and an increase in strength. The testing served as preliminary research to guide further studies into the topic. The natural powdery gypcrete samples, with high gypsum contents and a lot of fine material, and five prepared samples of differing gypsum contents, were subject to falling-head permeability tests using both water and brine. It is understood that particle size distribution contributes to the hydraulic conductivity of soils, where a higher portion fines results in a lower hydraulic conductivity. In the case of gypcrete, the solubility is of significance as well, as it may have long term effects, through leaching and eventual cavity formation. With the intent of evaluating the effect of the aforementioned factors on the hydraulic conductivity of gypcrete in South Africa, the samples used represent differences in particle size distribution, gypsum content and origin. All samples, both natural and prepared, resulted in similar k values, in the order of 7.26x10-6 m/s, for water and the brine, despite the differences in properties. The results show that while the hydraulic conductivity is believed to be influenced by particle size distribution and origin, in the case of gypcrete in South Africa, on a small scale, it remained largely consistent. / Dissertation (MSc)--University of Pretoria, 2019. / Geology / MSc (Engineering Geology) / Unrestricted

Roads are one of the most recognizable artifacts of human habitation and development. They cross various landscapes and expand with the increasing density of human settlements. While these structures are vital in facilitating vehicular transportation, they can also have unintended negative consequences for natural ecosystems, such as road-related wildlife mortality. To examine the negative impacts of roads on wildlife at a local level, I quantified the frequency and patterns of road mortality across a yearlong study period in a study area within Montgomery and Giles Counties in southwest Virginia. I also examined relationships between roadkill patterns and several land and road variables, hoping to close a current literature gap by focusing specifically on small and meso-mammals weighing less than 15kg. I recorded the location and species of carcasses found along predetermined routes, including roads with variable speed limits, road infrastructure, and adjacent land cover. I used government-provided data sets, satellite imagery, and field verification to characterize our study routes. I recorded 294 carcasses and identified 221, of which 84% were small or meso-mammals, including 11 taxa. The most frequent roadkill taxa were tree squirrels (Sciurus sp.), opossums (Didelphis virginiana), striped skunks (Mephitus mephitis), and raccoons (Procyon lotor). I found three roadkill hotspots, all along a major highway, and a high frequency of roadkill in spring, autumn, and early winter. High posted speed limits, the presence of artificial road lighting, and high proportions of forest and early successional growth cover (often present in pastures) were associated with an increased frequency of wildlife-vehicle collisions. / Roads are one of the most recognizable artifacts of human habitation and development. They cross various landscapes and expand with the increasing density of human settlements. While these structures are vital in facilitating automobile transportation, they can also have unintended negative consequences for natural ecosystems, such as roadkill. To examine the negative impacts of roads on local wildlife, I studied the frequency, patterns, and causes of road mortality across a year-long study period. I also examined relationships between frequent roadkill hotspots and several land and road variables in a Montgomery and Giles Counties study area in southwest Virginia. My project focused on small and medium-sized mammals because they are rarely considered in other roadkill studies. I collected field data on the location and species of carcasses observed on surveys along predetermined routes, including roads with variable speed limits, road infrastructure, and adjacent land cover. I used government-provided data sets, imagery, and field verification to characterize study routes. I recorded 294 carcasses and identified 221, 84% of which were small and medium-sized mammals. Roadkill frequency was highest in spring, autumn, and late winter. I found that high posted speed limits, the presence of artificial lighting, high forest cover, and high early successional growth cover (such as shrubbery and small trees in pastures) were associated with a higher frequency of wildlife-vehicle collisions.

Catch Chain is a book of poems that traces the journey of a Corrections Officer who attempts to combat issues of isolation, inhumane treatment of inmates and societal rejection in jails by embarking upon a cross-country road trip. However, the same issues the officer initially wrestled with begin cropping up in different cities, on various highways and in a multitude of states. The excitement and adventure of the open road runs parallel to the recurring imprisonment of the guard's mind. / Master of Fine Arts

This dissertation presents an approach to reconstruct degenerate near-planar road surface in three-dimensional (3D) while automatically detect road defects. Three techniques are developed in this dissertation to establish the proposed approach. The first technique is proposed to reconstruct the degenerate near-planar road surface into 3D from one camera. Unlike the traditional Structure from Motion (SfM) technique which has the degeneracy issue for near-planar object 3D reconstruction, the uniqueness of the proposed technique lies in the use of near-planar characteristics of surfaces in the 3D reconstruction process, which solves the degenerate road surface reconstruction problem using only two images. Following the accuracy-enhanced 3D reconstructed road surface, the second technique automatically detects and estimates road surface defects. As the 3D surface is inversely solved from 2D road images, the detection is achieved by jointly identifying irregularities from the 3D road surfaces and the corresponding image information, while clustering road defects and obstacles using a mean-shift algorithm with flat kernel to estimate the depth, size, and location of the defects. To enhance the physics-driven automatic detection reliability, the third technique proposes and incorporates a self-supervised learning structure with data-driven Convolutional Neural Networks (CNN). Different from supervised learning approaches which need labeled training images, the road anomaly detection network is trained by road surface images that are automatically labeled based on the reconstructed 3D surface information. In order to collect clear road surface images on the public road, a road surface monitoring system is designed and integrated for the road surface image capturing and visualization. The proposed approach is evaluated in both simulated environment and through real-world experiments. The parametric study of the proposed approach shows the small error of the 3D road surface reconstruction influenced by different variables such as the image noise, camera orientation, and the vertical movement of the camera in a controlled simulation environment. The comparison with traditional SfM technique and the numerical results of the proposed reconstruction using real-world road surface images then indicate that the proposed approach effectively reconstructs high quality near-planar road surface while automatically detects road defects with high precision, accuracy, and recall rates without the degenerate issue. / Doctor of Philosophy / Road is one of the key infrastructures for ground transportation. A good road surface condition can benefit mainly on three aspects: 1. Avoiding the potential traffic accident caused by road surface defects, such as potholes. 2. Reducing the damage to the vehicle initiated by the bad road surface condition. 3. Improving the driving and riding comfort on a healthy road surface. With all the benefits mentioned above, it is important to examine and check the road surface quality frequently and efficiently to make sure that the road surface is in a healthy condition. In order to detect any road surface defects on public road in time, this dissertation proposes three techniques to tackle the road surface defects detection problem: First, a near-planar road surface three-dimensional (3D) reconstruction technique is proposed. Unlike traditional 3D reconstruction technique, the proposed technique solves the degenerate issue for road surface 3D reconstruction from two images. The degenerate issue appears when the object reconstructed has near-planar surfaces. Second, after getting the accuracy-enhanced 3D road surface reconstruction, this dissertation proposes an automatic defects detection technique using both the 3D reconstructed road surface and the road surface image information. Although physics-based detection using 3D reconstruction and 2D images are reliable and explainable, it needs more time to process these data. To speed up the road surface defects detection task, the third contribution is a technique that proposes a self-supervised learning structure with data-driven Convolutional Neural Networks (CNN). Different from traditional neural network-based detection techniques, the proposed combines the 3D road information with the CNN output to jointly determine the road surface defects region. All the proposed techniques are evaluated using both the simulation and real-world experiments. Results show the efficacy and efficiency of the proposed techniques in this dissertation.

The cost of a road construction over its service life is a function of design, quality of construction as well as maintenance strategies and operations. An optimal life-cycle cost for a road requires evaluations of the above mentioned components. Unfortunately, road designers often neglect a very important aspect, namely, the possibility to perform future maintenance activities. Focus is mainly directed towards other aspects such as investment costs, traffic safety, aesthetic appearance, regional development and environmental effects. This doctoral thesis presents the results of a research project aimed to increase consideration of road maintenance aspects in the planning and design process. The following subgoals were established: Identify the obstacles that prevent adequate consideration of future maintenance during the road planning and design process; and Examine optimisation of life-cycle costs as an approach towards increased efficiency during the road planning and design process. The research project started with a literature review aimed at evaluating the extent to which maintenance aspects are considered during road planning and design as an improvement potential for maintenance efficiency. Efforts made by road authorities to increase efficiency, especially maintenance efficiency, were evaluated. The results indicated that all the evaluated efforts had one thing in common, namely ignorance of the interrelationship between geometrical road design and maintenance as an effective tool to increase maintenance efficiency. Focus has mainly been on improving operating practises and maintenance procedures. This fact might also explain why some efforts to increase maintenance efficiency have been less successful. An investigation was conducted to identify the problems and difficulties, which obstruct due consideration of maintainability during the road planning and design process. A method called “Change Analysis” was used to analyse data collected during interviews with experts in road design and maintenance. The study indicated a complex combination of problems which result in inadequate consideration of maintenance aspects when planning and designing roads. The identified problems were classified into six categories: insufficient consulting, insufficient knowledge, regulations and specifications without consideration of maintenance aspects, insufficient planning and design activities, inadequate organisation and demands from other authorities. Several urgent needs for changes to eliminate these problems were identified. One of the problems identified in the above mentioned study as an obstacle for due consideration of maintenance aspects during road design was the absence of a model for calculating life-cycle costs for roads. Because of this lack of knowledge, the research project focused on implementing a new approach for calculating and analysing life-cycle costs for roads with emphasis on the relationship between road design and road maintainability. Road barriers were chosen as an example. The ambition is to develop this approach to cover other road components at a later stage. A study was conducted to quantify repair rates for barriers and associated repair costs as one of the major maintenance costs for road barriers. A method called “Case Study Research Method” was used to analyse the effect of several factors on barrier repairs costs, such as barrier type, road type, posted speed and seasonal effect. The analyses were based on documented data associated with 1625 repairs conducted in four different geographical regions in Sweden during 2006. A model for calculation of average repair costs per vehicle kilometres was created. Significant differences in the barrier repair costs were found between the studied barrier types. In another study, the injuries associated with road barrier collisions and the corresponding influencing factors were analysed. The analyses in this study were based on documented data from actual barrier collisions between 2005 and 2008 in Sweden. The result was used to calculate the cost for injuries associated with barrier collisions as a part of the socio-economic cost for road barriers. The results showed significant differences in the number of injuries associated with collisions with different barrier types. To calculate and analyse life-cycle costs for road barriers a new approach was developed based on a method called “Activity-based Life-cycle Costing”. By modelling uncertainties, the presented approach gives a possibility to identify and analyse factors crucial for optimising life-cycle costs. The study showed a great potential to increase road maintenance efficiency through road design. It also showed that road components with low investment costs might not be the best choice when including maintenance and socio-economic aspects. The difficulties and problems faced during the collection of data for calculating life-cycle costs for road barriers indicated a great need for improving current data collecting and archiving procedures. The research focused on Swedish road planning and design. However, the conclusions can be applied to other Nordic countries, where weather conditions and road design practices are similar. The general methodological approaches used in this research project may be applied also to other studies.