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(PS-2413) Extracting the Resource-Constrained Critical/Longest Path from a Leveled Schedule

Level: Advanced
Author(s): Thomas M. Boyle, PE PSP
Venue: 2017 AACE International Annual Meeting, Orlando, FL

Abstract: Heuristic (i.e. rule-based) resource leveling is the only method explicitly provided for avoiding resource conflicts in the dominant North American scheduling software, but it seems largely rejected in the construction industry because conventional Critical Path definitions and corresponding Float calculations in leveled schedules can be wrong or misleading.

The author describes an automated method for accurately depicting the Resource-Constrained Driving Path to project completion – i.e. the Critical Path – in a leveled schedule. The method infers resource-driven, Finish-to-Start links between time-adjacent activities based on detailed examination of the corresponding resource assignments and leveling data. These latent links can then be incorporated into a robust routine for tracing and reporting driving logic. This method is demonstrated in Microsoft Project; implications for a similar approach in Primavera P6 are outlined. Limitations of the method are explored and described using standard resource-loaded schedule models.

The sequence of activities in a leveled schedule can be notably unstable from month to month, as small deviations in work completion can lead to substantial changes in the sequences (and dates) of future work . The method presented in this paper allows practical and repeated use of automatic resource leveling while maintaining a clear definition of the true Critical Path through the project.