Critical Path Method Project Management

CPM The critical path method (CPM): As applied to construction projects The critical path method (CPM) was originally developed by the DuPont Company in the 1950s as a method of project management when DuPont shutting down its chemical plants for maintenance work. The shutdown process was complex and detailed, and had to be deployed in a highly regimented fashion in terms of the completion of steps and coordination of the workforce (CPM, 2011, Net MBA).

Yet the process also demanded a certain amount of flexibility in terms of managing unexpected delays, as well as the need to reduce costs. Ever since its inception, other companies have been using the CPM method to optimize efficiency and reduce costs. Now it is most often used in the construction, architectural, and engineering industries to manage a project with multiple components. The method is graphical in nature and thus is ideal to deploy for a multi-stage project. "CPM models the activities and events of a project as a network.

Activities are depicted as nodes on the network and events that signify the beginning or ending of activities are depicted as arcs or lines between the nodes" (CPM, 2011, Net MBA). At the beginning of the CPM process, project managers specify the individual activities they must perform to ensure the project's completion, sequence these activities, and create a diagram with an estimation of the overall completion time. Then they identify the 'critical path' or the longest time that will be needed to complete the entire journey from beginning to end.

The model is updated as the project progresses. "The basic CPM terms are Early Start and Early Finish (collectively known as Early Dates), Late Start and Late Finish (collectively known as Late Dates), and Total Float (the amount of time that an activity can float between the Early and Late Dates without delaying the project completion date)" (About CPM, 2011, PMSB). Ideally, there should be a relatively narrow range of time between late and early start dates.

Projects in which various nodes have a wide range of 'wiggle room' for delay are more likely to be completed on time and are less likely, therefore, to incur additional costs. "The available Total Float can be used to efficiently allocate resources or to accommodate unforeseen events or scope changes. Total Float is generally considered a shared resource between team members. Once the Total Float is consumed, additional planning adjustments (relationships and/or duration estimates) must be made or the project completion will be delayed" (About CPM, 2011, PMSB).

In the language of CSM charts, activities are enclosed discrete elements, such as laying-down of the foundation of a building. The activity stages are represented as numbered 'nodes.' "You connect the nodes with arrows or 'arcs' that represent the activities that are listed" (Baker 2004). Graphically, events appear as circled numbers and lines are used to connect the numbered circles to represent dependencies (CPM, 2010, UGDSB).

There should be a single starting point and ending point, although some nodes may not have any contingent successors and predecessors (for example, the marketing of a group of development houses may be ongoing, and not necessarily dependent upon the project's physical construction, other than the need for its completion).

CPM is a useful part of the planning process of a construction project because it allows the involved parties to estimate which project are 'critical' in the sense that they must be completed on time, or else result in costly delays. Construction projects are easily stymied and can run months, even years over the estimated duration simply because one or two critical elements take longer than expected.

(An excellent example of this is the infamous 'Big Dig' construction project in Boston, which was beset by delays during critical junctions of the construction process). Once the most critical components of the project are determined, "if you put in information about the cost of each activity, and how much it costs to speed up each activity, CPM can help you figure out whether you should try to speed up the project, and, if so, what is the least costly way to speed up the project" (Baker 2004).

A cost-benefit analysis of speed vs. financial outlays must always be conducted. A slower project costs more in labor, for example, but hiring additional workers and equipment may ultimately not save money for the project managers in the long run. Optimal use of CPM allows managers to find a balance between the scope of the project, its budget, and the best ways to use labor, equipment, and capital. Even under the best of circumstances, however, projects can become conflicted. "The.