Join Bonnie Biafore for an in-depth discussion in this video Delaying or overlapping tasks with lag and lead time, part of Project Management Foundations: Schedules.
Some linked tasks have delays between them, while others overlap. You use Lag Time, positive or negative, to create these delays or overlaps. Positive lag time creates a delay between linked tasks. Waiting for paint to dry before installing carpet is one example of lag time. If you use a scheduling program you can add lag time to any task dependency that needs it. To add a two day lag, all you have to do is fill in two days in the lag field. An Overlap is when two tasks run simultaneously for part of their duration.
The method you chose to create an overlap really depends on how you view the relationship between the tasks. Earlier we looked at the task dependence between Write content and Edit content. If the Editor is ready to work the dependency can be Start to Start, but the Editor needs something to edit. So the dependency needs some lag time to allow the writers to complete a training module. What if you only bring in an editor when there's editing to do? In that case, the dependency between the tasks looks more like Finish to Finish.
The editor finishes editing two days after the writing is finished. Although you use a different type of dependency, you would still use positive lag time. If tasks overlap just a little, the relationship might be easier to follow if you link the tasks finish to start. Then, negative lag creates the overlap between the tasks. How do you start the second task before the first one is done? By adding negative lag to the task dependency. Here's an example of how negative lag creates an overlap.
You plan to test the orientation website after it's built, so you link the tasks Finish to Start. But the schedule is too long, so you decide to start testing s few days before the website is finished. Lag time in task dependencies help you model how work really occurs. It can also help you build a more efficient schedule, or shorten one that's too long.
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- Identifying the work that needs to be done
- Adding milestones
- Delaying or overlapping tasks with lag and lead time
- Assigning resources
- Balancing workloads
- Adding buffers and baselines to the schedule
- Uncovering and correcting out schedule problems<br><br>
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