Critical Path

The critical path concept is used by project managers to determine the latest completion date for a project. The term path is used figuratively, to denote navigating a complex set of project tasks and critical activities that will lead to the latest possible completion date. In the sample project network diagram below, the critical path is illustrated with a red line.

A flowchart with five nodes representing work packages and black and red arrows representing dependencies. Four nodes are connected by red arrows, identifying the critical path. One node is connected only by black arrows and so is not on the critical path.
The Critical Path

Source: Illes

An estimated project completion date can be identified after three steps have been completed: (1) the deliverables have been identified in the work breakdown structure, (2) the duration needed for each activity to produce deliverables (with the triple constraints in mind) has been determined, along with the earliest start, earliest finish, latest start, and latest finish dates, and (3) the dependencies between activities have been represented (Jones, 2008). A dependency usually means that an activity cannot begin without the deliverables from one or more preceding activities. You might think of the critical path as the longest set of project activities that must be completed in a defined order. If a delay occurs in any activity on the critical path, the project completion date will be moved by an equal amount of time. On the other hand, it is likely that relatively short delays in activities that do not lie on the critical path will not cause a change to the project completion date.

References

Jones, C. (2008). Moving from the WBS to a critical path schedule. Paper presented at PMI Global Congress 2008—North America, Denver, CO. Newton Square, PA: Project Management Institute.

Licenses and Attributions

5n PERT graph with critical path by Illes is in the public domain. UMGC has modified this work.