Abstract: Time, cost, quality and safety, are the four critical elements that contribute to project success. Traditionally, literature has focused on analysing only time and cost. Subsequently, other multi-objective optimization methods developed to optimize time, cost, quality or safety have been developed. New types of contracting methods designed by governments, included maximizing construction quality while minimizing its time and cost. Recently, due to the fact that the construction industry suffers from more accidents of greater severity than other industrial sectors, safety has become one of the four critical elements that contribute to project success. The project scheduling literature largely concentrates on the generation of a precedence and resource feasible schedule that optimizes the scheduling objective and that should serve as a baseline schedule for executing the project. However, these models do not allow to analyse alternative work plans that consider the trade-offs between time, cost, quality, and safety. In this paper, an integer linear programming problem is applied to a decision-CPM network in order to obtain an overall optimum including time, cost, quality and safety in a road building project. Using this type of model, the effects of alternative methods of performing the tasks can be considered and a greater degree of interaction between the planning and scheduling phases of a project is obtained.
