The discrete time–cost tradeoff problem revisited

In the management of a project, the project duration can often be compressed by accelerating some of its activities at an additional expense. This is the so-called time–cost tradeoff problem which has been studied extensively in the project management literature. However, the discrete version of the problem, encountered frequently in practice and also useful in modeling general time–cost relationships, has received only scant and sporadic attention. Prompted by the present emphasis on time-based competition and recent developments concerning problem complexity and solution, we reexamine this important problem in this paper. We begin by formally describing the problem and discussing the difficulties associated with its solution. We then provide an overview of the past solution approaches, identify their shortcomings, and present a new solution approach. Next, we present network decomposition/reduction as a convenient basis for solving the problem and analyzing its difficulty. Finally, we point to several new directions for future research, where we highlight the need for developing and evaluating effective procedures for solving the general time–cost tradeoff problem. To the best of our knowedge, the popular project management software packages do not include provisions for time–cost tradeoff analyses. Our work, we hope, will provide the groundwork and an incentive for alleviating this deficiency.