Part 91 Leads and Lags
(Project Schedule Management: Sequence Activities)
(Project Schedule Management: Develop Schedule)
(Project Schedule Management: Control Schedule)

  • In scheduling activities, we have Leads and Lags
  • Leads and Lags allow us to introduce flexibility into the schedule
  • A LEAD
    • Amount of time that a Successor Activity can be advanced before a Predecessor Activity
    • Represented by a negative value
    • For example, we can start the landscaping immediately after clean-up of the construction site, or we can wait up to two weeks
  • LAG
    • Amount of time that a Successor Activity can be delayed after a Predecessor Activity
    • Represented by a positive value
    • For example, we can start the shopping for furniture immediately after construction is complete, or we can start shopping up to one month before (since we know what the layout and color scheme of the house will look like)
  • Precedence Diagramming Techniques and Leads and Lags are used together
  • When we introduce a Lead or a Lag, we are making assumptions about how activities fit together in the schedule.  We are assuming (for the most part) that the lead or lag won’t affect other portions of the project.  We should document these assumptions.