What is Critical Path?
Let’s quickly review. The critical path is the longest path through the project and therefore sets the boundary for the shortest time to complete the project. Since it is the longest path, all other paths are shorter and should not impact the end of the project. To accelerate the project, you must accelerate the critical path. A delay on the critical path will automatically cause a delay on the project.
Critical path is typically calculated using project management software. In order to calculate the critical path, the project manager must first create a network diagram linking all project tasks and activities. With the network diagram or flowchart of the project activities set, then estimate a duration for each task. With this information the longest sequence of tasks from start to finish on the project can then be determined. That sequence is the critical path. It is not necessarily the most difficult path; it is the longest duration path.
Why Is Critical Path Seldom Calculated?
I frequently ask project managers if they know their critical path. The typical answer is that they know what it is. When I ask to see their calculations or the schedule chart that shows the critical path they start dodging. They tell me that they haven’t actually done the calculations, but they know what the critical path is. When I ask them to give me the sequence of events, it is often just a list of several difficult tasks that many times are not even linked together. At that time it is obvious that they do not know their critical path.
Calculating the critical path requires that the project manager have all the project tasks for the project, or at least a phase of the project. This can quickly expand to be what the project manager perceives to be unmanageable.
I was working with a company recently on a development project. We created the network diagram for just one deliverable in one phase and that network diagram had over 400 tasks in it and would take about six months. This wasn’t because we were trying to micromanage and created miniature tasks, it was because there were several departments and several locations involved. Each had activities to do and these were followed by a number of coordination activities between everyone. That was just one deliverable in one phase for the project. To do the entire phase would be about 2,000 tasks and the entire project would be over 5,000 tasks. The project manager was overwhelmed by the thought of creating a project schedule with that much complexity – so he didn’t.
This illustrates one of the problems. Most project managers do not have a schedule that is detailed enough to actually determine a critical path. And the creation of a detailed schedule could be an enormous undertaking for the project manager, even with the use of software. So project managers don’t have a detailed schedule. They have a very high-level schedule that is often missing key points of intersection between activities. Yet these points of intersection will drive the determination of the critical path.
So what is the answer? It depends upon how important schedule is on the project. If schedule achievement is critical and there is significant business benefit for schedule acceleration, the project needs to invest in a detailed network diagram that has all the points of intersection mapped out. Yes this is work, but without it, you cannot determine the critical path. If schedule is not the most important aspect of project success, then I would not invest in the effort to create and maintain the schedule.
How Do You Use Critical Path Information?
I often hear senior managers ask a project manager what is their critical path. Even if a project manager provides that to the senior managers, they do nothing with it. The critical path determines how fast the project can finish. If the managers want the project to finish faster, they should be asking what can be done to shorten tasks on the critical path. They should also be working with their people to ensure they are prepared to immediately start work on critical path tasks that are in their department. I have seen numerous delays on critical paths because the individual who was scheduled to start the “next task” on the critical path is not prepared. This is as much a failure of senior management as the project team.
Once the critical path is identified, the project manager needs to pulse the critical path task every day – maybe twice a day. A delay of even a day on the critical path is a delay to the end of the project. This pulse is to find if there are any problems and if there are to immediately start to fix them. The second thing the project manager needs to do is to warn the individuals on the next task that they are about to be the critical path. They can get ready to start immediately. The handoffs between tasks are where most of the time is lost on the critical path.
So where do chickens fit into this? When I was a young project manager I was leading a sub-project on a large enterprise-wide project. The overall project had thousands of tasks and activities across many departments. We were behind schedule and a new project leader introduced a critical path awareness technique – the rubber chicken. We had to set up our detailed schedules and a project critical path was determined. Whoever was managing the task that was currently active on the critical path had to carry a rubber chicken around with them at the office. If you were at your desk, the chicken was on the desk. If you went to a meeting the chicken went with you. The only way to get rid of the chicken was to complete the task and hand the chicken to the individual leading the next critical path task. This was a fun visual reminder of the critical path and it helped to keep the entire organization focused on accelerating the project to reach the schedule goals.
On a large project, critical path management is not easy. However, by doing the calculations and managing the handoffs, it will help you achieve the schedule goals.