Requests to shorten the project schedule and finish earlier are a regular part of managing a project. The first requests to shorten the schedule come almost immediately after you release the first draft of the schedule, when the project is still in the planning phase. The sponsor and stakeholders all come to you with reasons why the project needs to finish earlier. You need the correct techniques to address these requests or you will wind up promising durations that are impossible to deliver. Project Schedule & Software Main Page
The second batch of requests to shorten the project schedule come shortly after you launch the project. That’s when executives and other stakeholders begin to realize how your project may affect other projects in the organization. That’s when the new requests for an earlier finish date arrive on your desk. Again, you need to know the proper techniques. The objective is not to deny all of these requests to shorten the project duration. If you take that approach, your relationships with the stakeholders will go downhill fast. Plus you will usually get overruled. Project Status Reports
You need to focus on preserving the feasibility of the project in the face of these requests to finish earlier. There’s nothing wrong with shortening the duration of the project if you secure additional resources to do it or you can get approval to reduce the scope of the project to allow shortening of the duration. Finally, you can shorten the duration if you get additional budget to pay overtime or hire outside contractors.
Successful project managers don’t just promise to shorten the duration and figure out how to do it later. They develop the data to show the sponsor and stakeholders alternative ways of shortening the duration. These are never free. There are always trade-offs in the project scope, cost, duration or risk for shortening the duration. Let’s look at how you develop the data for trade-offs.
Project Schedule: Critical Path to Model Changes
You use the critical path method to identify the most efficient way to shorten the project duration. The first step is to use your project software to calculate the duration of every path (sequence of tasks) in the project. The path or sequence of tasks with the longest duration is the critical path and controls the project duration. All the other paths have slack or float. That is, they can finish later than currently scheduled and not delay the overall project completion date. This is significant because when you need to shorten the project duration, you do so by shortening the critical path. Reducing the duration of tasks in the project that are not on the critical path will allow those tasks to finish sooner but will not shorten the overall project duration. Critical Path
Once the project software identifies the tasks that are on the critical path, you can consider various options for shortening the duration of that path. Those options would include “crashing” the project by adding resources to critical path tasks so they finish sooner. As you are adding resources to the critical path tasks, you need to check to see if the critical path has changed. As you add resources to the tasks on a given path, the duration of that path decreases. Once another path has the longest duration, it becomes the critical path. Adding more resources to any tasks not on the critical path will not affect the duration of the project.
Let’s summarize everything we’ve covered.
When Do You Use the Critical Path?
You use the critical path technique when you need to shorten the duration of the project. The most common situation is when the initial draft of the schedule takes longer than the sponsor wants. You also use it to develop solutions for variances and to handle change requests.
Why Do You Use the Critical Path?
You use the critical path technique because it identifies where to add resources to reduce the project duration. Adding resources to the critical path tasks, (the longest path in the project) is much cheaper than adding resources to all of the tasks. The reason is that the other paths have slack; they can finish later than scheduled without delaying the project completion. It’s always useful to identify the critical path as you near the end of your project scheduling process. By knowing the critical path and how much slack the other tasks in the project have, you can identify opportunities for shortening the duration.
Project Schedule: Finish Earlier Example
Let’s examine a project with three paths. Each task in the path is identified with an alphabetic letter so the path ABDE starts with task A, then goes to B, then to D and ends with E. Here are the durations of each of the three paths and the amount of slack they each have.
Path ABDE: 10 days duration, 4 days of slack
Path ACFE: 14 days duration, 0 days of slack
Path ADGE: 13 days duration, 1 day of slack
You see that path ACFE has the longest duration, which is 14 days. You also see that path ACFE has no slack. When the path has no slack, the tasks on it cannot finish later than the baseline schedule without increasing the duration of the project. When they have slack, they can increase their duration until they use up all of their slack. At that point, that path becomes the critical path.
Chris Pimbock was a new project manager in his organization and he was preparing the schedule to present to the project sponsor. The sponsor was very clear during the initial planning session that the project had to be finished within 45 days. When Chris checked the first draft of the schedule, the duration of the project was 50 days. Chris knew he had to shorten the project duration. Chris calculated the duration of each of the four paths through the project and found that the critical path was indeed 50 days long. However, the other three paths were all less than 40 days. Chris then examined the five tasks that were on the critical path and found that one task, the engineering work, had 20 day duration. That told Chris that the easiest place to shorten the project duration by 5 days was the task with the 20 day duration. Chris looked at the resources assigned to that task on the critical path and found that one engineer was assigned to do 160 hours of work.
Chris contacted the engineering department and asked if a second engineer might be available to help on the task. In discussing options with the manager, Chris also specified that if they added a second engineer, both engineers could be finished within 10 days rather than the original 20 day schedule. The engineering department manager agreed to supply a second engineer to the project and Chris rescheduled the whole project. The duration was now 40 days and that allowed Chris to present a schedule that had 5 days of slack. That meant that the critical path tasks could slip by 5 days and the project would still finish on time.
Chris Pimbock was able to meet the project sponsor’s requirement without promising a duration that was faster than he could deliver. The key here was using data to show the sponsor exactly what had to happen to shorten the duration. This wasn’t a matter of leadership or inspiration of the project team, it was a matter of mathematics.
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