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Reviews the value of network concepts as a means of portraying complex logistics and distribution systems. Reports on research which focuses on the broader issues of model formulation and solution techniques rather than specific applications. Addresses the issues of designing networks with a tree structure, and also more general ones in which loops are allowed and redundancy enforced. The decision variables involved are related to whether or not a link should exist between two specific pairs of nodes, and then what should be the level of traffic flow on that particular link. Describes the design problem in detail and possible models that could be used to represent it. Follows with a description of genetic algorithms to solve the synthesis problem of deciding the node‐link topology, and the use of linear and non‐linear programming to solve the problem of assigning traffic flow to a network with a given typology in a least‐cost manner. Concludes with a description of computational experience with solving such problems.

The provision of affordable urban sanitation presents a unique set of challenges as the lack of space and resources to construct new latrines makes it necessary to empty existing pits, typically done manually with significant health risks. Various mechanised technologies have been developed to facilitate pit emptying, which are currently either tested on faecal sludge or an 'ad-hoc' simulant that (in the opinion of the tester) approximately replicates the behaviour of faecal sludge. This ranges from a watery consistency in some pour-flush latrines to the strong soil found in many alternating pits, making it difficult to evaluate the effect of changes to a design, or to compare the performance of different pit-emptying technologies produced by different organisations in different countries. This study developed the portable penetrometer, a man-portable device to physically characterise pit latrine sludge through in-situ measurement of its shear strength. The machine produces continuous profiles of shear strength with depth and is capable of testing to approximately 2.5 m below the slab. The portable penetrometer was manufactured and tested in the UK, before profiling approximately 30 pits in Kampala, Uganda. The resulting data are compared to the literature on the physical properties of faecal sludge, and are found to significantly extend the measured strength range with a maximum value approximately 5 times higher than previously reported. The effect of physical remoulding is identified through comparison of data from undisturbed and remoulded strength tests and highlights the potential to increase the 'pumpability' of faecal sludge through in-pit fluidisation.The implications for the development of pit-emptying technologies and synthetic sludge simulants are discussed, and potential further work is identified. These include studies on factors affecting pit function and fill-up rates as well as scientific tests on the effect of modifications to latrines. In both cases any change in the physical properties of the faecal sludge can be identified through repeated profiling using the portable penetrometer. It is hoped that the penetrometer can contribute to an improved understanding of the physical properties of faecal sludge and the factors affecting pit function, supporting the development of improved faecal sludge management services.

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