Expansion of the rural road network in Ethiopia requires the availability of low-cost materials for road construction, including capping layer and subgrade improvement, sub-base, base course, gravel wearing course and bituminised surface treatment. A reluctance to use cinder gravels for these purposes in the past has stemmed from the view that their properties, in terms of grading and CBR strength, are marginal and highly variable when compared to international specifications for road works. The geographical variability in Ethiopian cinder gravel geochemistry and engineering properties is described and comparisons are made with engineering geological field descriptions and cinder cone morphology, leading to the conclusion that maars and steep-sided, well-defined cones tend to yield the better-quality materials. The performance of trial sections of road constructed using cinder gravel is assessed and combined with the results of laboratory testing to develop a guideline for the wider use of the material in roadworks, either directly or through processes of blending, alternative compaction methods and cement stabilisation to yield a product that can be considered Bfit for purpose^for a range of uses in low-volume road construction.
Low-volume roads (LVRs) constitute an integral component of the road system in all developing countries, where their importance extends to all aspects of the social and economic development of rural communities. However, the original documentation relating to the provision of such roads is based in many respects on technology and research carried out in Europe and the United States some 30 to 40 years ago in environments very different from those prevailing in developing countries. As a result, these traditional approaches are often inappropriate for application in developing countries. Moreover, they tend to focus on the technical environment of road provision, with inadequate consideration of other interrelated environments that critically influence the types of LVRs that should be provided. As a result, a need for new, more holistic approaches to low-volume road provision has been engendered to satisfy the various needs of rural communities in a more sustainable manner. The objective of this discussion is to provide an insight into new, more holistic and sustainable approaches to the provision of LVRs in developing countries. Embodied in these new approaches is a need to rethink the old ways of providing such roads based on research and development work that has been carried out in these countries during the past 20 years. Examples include aspects of planning and project appraisal, geometric and pavement design, construction and drainage, and environmental issues, all of which need to be reconsidered in a more appropriate manner.
Pooling, or ride-sharing, is a term coined in the United States (U. S.) to describe various forms of collective travel organised for, and often by, specific groups of commuters with similar travel requirements. Its different forms include bus pooling (financially self-supporting works bus or commuter coach services), minibus pooling (van pooling in U.S. terminology) and car pooling. It has been claimed that these forms of collective travel offer a more personalised service than conventional stage carriage buses, and therefore have a greater chance of attracting solo car drivers and increasing vehicle occupancies. This, in turn, can lead to lower fuel consumption and reduced traffic congestion at peak times. Following the advent of oil shortages in the winter of 1973/74, considerable efforts were made in the U.S. to promote pooling initiatives. This gave rise to the publication of a substantial volume of literature that sometimes indicated significant resource-saving achievements. This paper considers the potential for bus, minibus and car pooling in Great Britain, drawing both on relevant theoretical and economic studies, and on practical operational experience. It concludes that under reasonable assumptions about the transport situation in the next decade or so, pooling could become increasingly useful for solving the travel problems of individual local groups, but that it is unlikely to become a major mode in terms of the numbers of trips carried. The effects of recent legislative changes are discussed, and the justification for further change assessed. Relevant comparisons are made with the U.S.
The problem outlinedThe question of land tenure is now beginning to assume an ever-increasing importance in Northern Rhodesia. This is not surprising, in fact it is inevitable' in any African territory that is changing as fast politically, socially and economically as is Northern Rhodesia today. The old patterns of land usage and land tenure cannot possibly maintain the ever-increasing population, a population that is moreover demanding more and more in terms of a higher standard of living. National productivity must rise, and fast, if the social pressures now building up are to be controlled and directed into peaceful and useful avenues. Much of the increase must and will undoubtedly come from the urban areas -from an ever-increasing degree of industrialization and specialization -but the fact still remains that a very large part of our indigenous population is a rural one. To them agriculture is, and will remain for several decades to come, their primary occupation and their primary source of wealth. It is therefore vital that agriculture be made more productive, and at the same time less damaging to the natural resources of the territory than it is at the moment. This is a formidable undertaking.Agriculture in Northern Rhodesia today is, with local exceptions, in a very primitive form. There is a great dearth of capital, of technical knowledge, of suitable cash crops, and perhaps above all, of incentive. This last point is frequently overlooked; it has at its roots the attitude to land that is so characteristic of most Bantu societies. To them, generally speaking, land is of vital importance to society as a whole, but it has no cash value, it is not sold or leased, and the individual's rights are either ephemeral or totally subservient to those of the society of which he is but a small part. As a result, there is little personal responsibility for land, little sense of personal and restricted ownership, and practically no incentive to improve it beyond the limits of subsistence cultivation.These traditional attitudes are now beginning to give way under the impact ofan increased population, through the realization that land is for production as well as for subsistence, to the specialization of occupation and to the influence of European ways of life.Where these forces are at their most powerful, in the Southern, Central and Eastern Provinces, there is arising a greater sense of personal ownership, but the changes are not fast enough for either the short term interests of those 1 See "Improved Farming in the Central Nyanza District -Kenya", by P. D. McEntee,
Despite evidence that the environment is a major factor in the performance of pavements with natural gravel road bases, this finding is rarely used fully in road design. Conventional design standards and specifications do not allow optimal use of local materials such as weathered basalt, cinder gravels, and laterites in low-volume road construction. Significant regional variations in climate are common in many African countries, including Ethiopia. This variation may provide opportunities, especially in drier areas and on well-drained soils, to relax national specifications, enhance use of local materials, and reduce construction costs. These are important factors that influence the provision of rural roads in Ethiopia. A range of naturally occurring materials was tested to determine their properties, particularly the relationship between strength (California bearing ratio) and moisture content. The samples tested included materials not currently considered suitable for road base and surfacing in Ethiopia. These road sections are being monitored to understand their behavior under local climatic conditions. Sections have been constructed in cut and fill and with sealed and unsealed shoulders. All materials showed higher strengths at lower moisture contents; but the strength–moisture relationships differed significantly for the different materials and for the same material at different compaction densities. The approaches developed for laboratory testing, together with evidence from ongoing and future trials, will enable Ethiopia to modify its national standards and specifications. Ethiopia will then be able to safely utilize the benefits of local variations in climate and pavement environment and increase the use of naturally occurring materials, thereby reducing construction costs by 45% to 60%.
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