Finance Easy 18 - How to Deal with Hanging Activities

Описание: Finance Easy 18
How to Deal with Hanging Activities

In some cases, when we determine the project schedule, we can identify multiple activities that have no successors and in some cases, this causes some concern because we find what we call "hanging activities" at the end of the project schedule when we use the precedence diagramming method (PDM).

In the first example we draw the schedule using the arrow diagramming method where the activities happen between events (fixed moments in time) and we see that the last events, even without successors end in the final event node and there are no hanging activities.

However, when we draw the diagram with the PDM, we see that there are two (or more) hanging activities and that makes some people nervous and they want to add an activity with duration 0. In the PDM, this is not possible, and when we add activities with duration 0 to the software, they are transformed immediately in milestones, hence we add a milestone at the end of the graph.

With the PDM, the backward pass with hanging activities is in many cases wrongly executed since for all paths, the LF is chosen equal to the EF of each ending activity and that is wrong. We have to select the EF of the longest path (= critical path) since all activities can finish at this time without changing the duration of the project.

This also leads to the wrong conclusion that there are multiple CPs since more paths have slack = 0 and we know that the CP = longest path throught he network