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Calculating and Executing a Forward and Backward Pass
When constructing a project schedule, a project manager can draw upon a score of strategic lessons from the game of football. For example, in wearing the hat of team coach, the project manager has at his fingertips a dynamic playbook of offensive and defensive moves to keep the project on schedule. During the early stages of the game, the project manager's focus is on developing realistic estimates for the project's schedule. The estimation process is accomplished by pulling from one of the early chapters of the playbook two essential plays: the forward pass and the backward pass. Analogous to the two minute drill, the forward pass is the best strategy for quickly driving the ball to the goal line or in the case of a project to the completion date. Each task represents a first down marker and the forward pass pushes the ball along the schedule in the least amount of time. A forward pass is executed by calculating the early start and the early finish for each task of the project. The early start is the earliest point in time when a task can be started. The early finish is the earliest point in time that a task could be finished. However, sometimes the forward pass is not the best strategy, particularly when the defense rushes the quarterback. In this case, the project manager needs to execute a backward pass to see if there is enough slack time to allow for a different set of plays and still get the project to the goal line before time expires on the clock. In constructing a backward pass, the project manager reverses the process to determine the late start and the late finish for each task in the project and remain in regulation time. The late start date is the latest point in time when a task can be started. The late finish is the latest point in time that task could be finished.
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Constructing the Forward and Backward Pass Project Management Template
You can easily constructing a forward and backward pass template in Microsoft Word by following these steps:
- To create the template which is illustrated below and in a downloadable version in the Project Management media gallery, open a Word document and insert an organizational chart.
- Choose the primary color style.
- Create levels to reflect predecessor and successor tasks.
- Fill-in values for each task's early start and early finish. Begin with Task 1 and label the early start (abbreviated ES on the template) as Day 0.
- Add the estimated duration of the task to the early start to calculate the early finish (abbreviated EF on the template).
- Label each successor task's ES as the EF of the predecessor's task.
- Where you have more than one predecessor for a task, use the later EF as the ES for the successor task.
- Fill-in values for each task's late start and late finish. Begin with the last task and label the late finish (LF) with the completion day determined by the forward pass.
- Subtract the duration from the LF to calculate the late start (LS).
- Where you have more than one predecessor for a task, use the later LS as the LF for the predecessor task.
Here is an illustration of the forward and backward pass template. Notice that the early start and late start begin at the same time (Day 0) and the late start and late finish end at the same time (Day 30), The difference between the early and late finish of any task is called the total slack or float. Remember that even if the project falls behind, the project manager's playbook still has a number of other options to get the schedule back on track. For more on executing what is known in football as a “no huddle play" continue reading this article to learn more on crashing or compressing the project schedule.