Letter to the Editor—Critical Path Planning—PERT Integration

The Critical Path Programming System, even though restricted to project planning situations in which network structure and activity statistics are invariant during reduction of project duration, is proving to be a practical and useful technique. In fact, the efficiency of the algorithm developed by Kelley (Kelley, James E., Jr. 1961. Critical-path planning and scheduling: mathematical basis. Opns Res.9 296–320.) for project time reduction permits one to adjust rapidly and inexpensively to changes in network structure or activity time-cost estimates as these changes develop. However, the effects of random variations in activity time estimates on earliest event occurrence time and project duration are not evaluated in the basic model described by Kelley, and the incorporation of the PERT procedure provides additional information concerning these effects.