Evaluating Project Scheduling and Due Date Assignment Procedures: An Experimental Analysis

Managers of construction projects, maintenance activities, auditing contracts, software shops, etc. are frequently faced with the task of establishing a new project's due date, which must compete with other projects already in progress or expected (forecasted) to start in the future. The study reported here addresses the problem of establishing due dates for projects which require limited resources, in an environment where new projects arrive continuously and randomly over time. A set of procedures is developed which set each project's due date when it arrives using information about the new project, current projects, and available resources. The due date setting procedures are tested via simulation with four activity scheduling heuristics that control the assignment of resources to specific activities of available projects. A second test demonstrates the performance of the due date procedures, where a portion of arriving projects have their due dates established by external forces beyond management's control. Performance measures of project mean completion time, project mean lateness, project standard deviation of lateness, and total tardiness (sum of all projects' tardy time) were collected for evaluation.

This study presents a number of important results for managers interested in scheduling projects and setting due dates. First, using more information concerning the current work in progress, available resources, and activity precedent relationships provides a better due date estimate for a new project. Second, a finite scheduling procedure (called SFT) consistently gives better due date estimates than simpler aggregate procedures. Third, when some project due dates are set externally, due date performance deteriorates. However, when SFT is combined with a due date oriented activity scheduling rule, due dale performance deterioration is less. Fourth, the effort, measured by CPU time, for SFT to estimate a good due date depends upon the ratio of activity resources required to total resources available, rather than the number of activities across all projects. And fifth, similarities and differences between the results observed in this study and past due date job shop scheduling research are reviewed.