It is generally accepted that the three major dimensions of project success are time, budget, and quality. Most of the research in project planning is focused on the time–cost trade–off, and only a few papers have considered the three dimensions together. This paper describes the evolution of formulations for optimising project time–cost and quality, and continues by developing a new, non–linear optimisation formulation that better reflects the triangular trade–off structure between time, budget, and quality. In particular, the Cobb–Douglas formula is adopted and its use is illustrated. The model is discussed, and the structure of the trade–off is analysed and illustrated.
Keywords: project management, project scheduling, project performance, project trade–offs, Cobb–Douglas function, project planning, time, budget, quality