How to Create a Backward Pass Analysis for Operations Management
When you’ve finished entering timing data for a forward pass analysis, you can create the backward pass analysis for your operations, which determines the latest times an activity can be started and finished without compromising the timing of the project as a whole. Follow these steps to complete this part of the diagram.
Set the latest finish (LF) time for the project by setting the LF of the END note equal to its EF time.
Mark this time in the lower-right corner of the End node.
Subtract the duration of the End node (0 days) from the latest finish time to get the latest start (LS) time.
That is, LS = LF minus Duration. Mark the LS in the lower-left corner of the node.
The LF time for all the activities in the diagram is equal to the LS time of its successor activity.
For example, the LF time of activity J is the LS time of activity K, which is 30.9 days. J’s duration is 0.15, so its LS time is 30.9 minus 0.15 = 30.75.
If an activity has several successors, its EF time is the earliest of the successors’ LS times.
Activity C has two successors, F and I. F’s LS time is 30, and I’s is 30.5. So C’s LF time is 30.
Repeat this process until you get back to the start node.
If the start node’s LS time is something other than 0, you’ve made a mistake.