Morgan R. Walker at DuPont and James E. Kelley Jr. at Remington Rand created the critical route technique in the 1950s. The World Trade Center’s Twin Towers were the first skyscraper to employ this technique when they were constructed in 1966. A blast in 1993 forced the facility’s repair crew to turn to CPM for help organising the operation, which was already running behind schedule.
To begin with, CPM was done by hand, using paper and a pencil as the only tools available. With the advent of PCs and the proliferation of mainframes, technology has made CPM a lot simpler. To plan project activities and create a visual depiction of project tasks and their links, software applications employ algorithms. We’ll go more into the significance of software later on.
The critical path method is a technique for analysing the schedule network using the schedule model. The critical path method determines the theoretical early and late start and finishes dates for all scheduled activities, regardless of resource constraints, by performing a forwards and backwards pass analysis through the project schedule network paths.
The subsequent early and late start and finish dates are not necessarily indicative of the project schedule; rather, they indicate the time periods within which scheduled activities should be scheduled, given their durations, logical relationships, leads, lags, and other known constraints.
Calculated early start and late finish dates may or may not be identical on any network path, as the total float, which allows for schedule flexibility, may be positive, negative, or zero. The schedule flexibility of any network path is quantified by the positive difference between early and late dates, which is referred to as “total float.”
Critical paths have a total float of zero or negative, and schedule activities that occur on a critical path are referred to as “critical activities.” Adjustments to activity durations, logical relationships, leads and lags, or other schedule constraints may be required to generate network paths with a total float of zero or positive. Once the total float for a network path is determined to be zero or positive, the free float — the amount of time that a schedule activity can be delayed without delaying the early start date of any immediate successor activity within the network path — can be determined as well.
What Is Critical in the Critical Path Method
When undertaking any project, from cooking to construction, you are aware that a specific amount of time is required to finish the task. This minimum time spans a succession of logically ordered steps. For instance, while baking a cake, these processes include mixing the mixture, baking the cake, allowing it to cool, and icing it.
A step can begin only once all preceding stages are accomplished. The total time required to accomplish these phases equals the time required to complete the project.
To continue with the cake illustration, you may wonder, “How about preheating the oven?” This stage can be executed concurrently with other jobs, thus it does not add to the project’s overall duration. Additionally, if the project is delayed, it will not always prolong the duration of the project.
Only those actions that contribute to the single longest series from start to finish count towards project duration: mixing, baking, cooling, and frosting. This sequence of actions is referred to in project management as the critical route, and the constituent parts are referred to as critical tasks.
The critical route method is a foundational technique for project schedule that is utilised in a wide variety of industries where time is money. It can be used by construction stakeholders to visualise and estimate the duration of a project, as well as a shorthand for discussing how duration is influenced as project variables change.
Construction project managers worldwide are familiar with a CPM chart, as they must study it in order to earn the Project Management Professional (PMP) certification. The CPM is a legal benchmark for quantifying project delays in project-related issues, and it is frequently used in court cases as the basis for financial claims.