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The problem of minimising the overall duration of a project subject to constraints on the availability of resources is considered with particular reference to the use of branch and bound methods. A new resource based bound, new dominance rules and an innovatory network breakdown technique which preserves optimality are reported. Computational experience and comparisons with schedules obtained by decision rule methods are given.

This paper describes two complementary studies concerning the maintenance and replacement of heavy haul railway track. Minimum cost policies are derived using decision networks in one case and a group replacement model in the other. The results indicate relatively large cost savings on current practice.

A case study of the application of two O.R. techniques for determining optimal shift sizes for telephone betting operators is described. The first formulation uses linear programming and the second, network flow techniques. The network flow model has a considerable computational speed advantage, but the L.P. model is currently in operation.

The problem of creating an activity-on-arrow network diagram from activity precedence data is considered. An heuristic is described which is incorporated into a computer program that can tackle problems of a practical size. Some computational experience is reported.