Best Practice 6: Confirming That the Critical Path Is Valid

Key Questions

  1. Is the critical path, or longest path (in the presence of date constraints), calculated by the scheduling software valid?

    1. Are any activities in the schedule missing logic or constrained without justification? Are these issues resulting in an unreliable critical path?
    2. Is the critical path a continuous path from the status date to the major completion milestones?
    3. Does the critical path start with a constraint so that other activities are unimportant in driving the milestone date? If so, is there justification for that constraint?
    4. Does the critical path include LOE activities? Is the critical path driven by activities of unusually long duration that are not considered planning packages?
    5. Is the critical path driven in any way by lags or leads?

  2. Does management use the critical path to focus on activities that will detrimentally affect key program milestones and deliveries if they slip?

Key Documentation

  1. Important program deliverables or milestones for which critical paths should be established are identified.

  2. Printouts of the logic diagram indicate the longest paths to the important milestones, as well as critical paths based on total float to all major milestones.

  3. Near-critical paths are identified.

Likely Effects If Criteria Are Not Fully Met

  1. Without a valid critical path, management cannot focus on activities that will detrimentally affect the key program milestones and deliveries if they slip.

  2. Unless the schedule can produce a true critical path, the program office will not be able to provide reliable timeline estimates or identify when problems or changes may occur and their effects on downstream work.

  3. Successfully identifying the critical path relies on capturing all activities (Best Practice 1), properly sequencing activities (Best Practice 2), horizontal traceability (Best Practice 5), the reasonableness of float (Best Practice 7), accurate status updates (Best Practice 9), and—if there are resource limitations—assigning resources (Best Practice 3).

  4. Unless the schedule is fully horizontally traceable, the effects of slipped activities on successor activities cannot be determined. If the schedule is missing dependencies or if activities are not linked correctly, float estimates will be miscalculated. Incorrect float estimates will result in an invalid critical path and will hinder management’s ability to allocate resources from noncritical activities to those that must be completed on time.

  5. LOE activities should not drive the schedule. If LOE is critical, management has no indication of which activities can slip and which will respond positively to additional resources to reduce the risk of finishing late.

  6. The review and analysis of near-critical paths is important because their activities are likely to overtake the existing critical path and drive the schedule.