The term critical path refers to an important concept in project management, and some project managers believe that it deserves the most attention during the project life cycle. The critical path refers to the sequence or order of schedule activities that will make up the entire duration of a project. It represents the longest path through the entirety of the project and typically this path consists of every single activity that must be concluded from the kickoff to the ultimate conclusion of the project. Being the longest path, it is also the shortest possible duration of the project.
Let’s look at an example. A house is being built, and windows and electricity are installed at the same time. Installing windows takes 1 day, installing electricity takes 3 days. If installing the windows takes 2 days, it will not affect the project duration. If installing electricity takes longer than 3 days, it does affect the project schedule. The electricity deliverable thus is on the critical path since a delay here will delay the entire project. At the same time, this activity cannot be bypassed so that this is the shortest possible sequence in the project.
Obviously, the critical path can change: If installing the windows takes 4 days due to difficulties, then the electricity activity will not be on the critical path anymore but the windows activity will be. As a consequence, focussing on the critical path alone may not be the ultimate solution. Work packages that are of high risk in terms of schedule delays should be under attention, too.
In some cases, a critical path can terminate on a particular schedule milestone that does not come at the conclusion of the project. In these cases, typically, the schedule milestone in question will have a finish that comes at a time no later than that of the imposed date schedule restraint in question. That said, in more cases than not the critical path does indeed run the entire life of a project. For more information, please see critical path method.
This term is defined in the 3rd and the 4th edition of the PMBOK.