Network Planning and Critical Path Method

Abstract

Scheduling a project is one of the main challenges in project management. According to ISO21502 the purpose of schedule management is to enable work to be undertaken in a timely manner and to reduce slippage to an acceptable level. The schedule should be an integrated part of the project’s plan and developed under the direction of the project manager .

There are several scheduling techniques that can be used to plan and estimate the duration of a project according to its complexity and uncertainty. One of the most common is the critical path method or CPM. This scheduling tool calculates the theoretical early and late start and finish dates for all activities, with no resource constraints, performing a bottom-up analysis forward and backward the entire network . The “critical path” is the longest sequence of activities that must finish in time to fully complete the project. However, it also determines the shortest period in which the project can be finished.

One of the benefits of using this tool is that allows to identify the most critical activities of the project. Moreover, if one of these is delayed, the project itself is compromised. Thus, it helps project managers to have a good overview in which task they must put more focus on. Nonetheless, CPM also has its limitations. In this article these disadvantages will be described and how to deal with them will be explained.

The Critical Path Method

History

During the early 1950s the traditional project management approach started to fail due to the complexity of coordinate multiples activities in the direction of the same project objective. Hence, the development of a tool that was able to organize the sequence of activities and schedule them was needed. The critical path method or CPM was developed in the 1950s by two engineers, Morgan R. Walker, working for the DuPont Corporation, and James E. Kelly working for Remington Rand. The development of this tool has its foundations on the work of DuPont Corporation from the earlier 1940s in the so recognized Manhattan Project.

Large building projects like the development of chemical and nuclear power facilities were the first ones to apply the critical route technique. Although it swiftly found uses in a variety of sectors, including as software development, manufacturing, and services. The 1960s and 1970s saw a significant increase in the use of CPM as a tool for managing big and complex projects. It was especially helpful for projects that called for the coordination of several interdependent activities as well as resources and timelines.

CPM is still often employed in project management today and is included in several project management software programs. The tool has also been modified to consider modifications in project management procedures, such as the expanding usage of Agile approaches and virtual teams.

See also

Bibliography

A Guide to the Project Management Body of Knowledge, fourth edition, 2008, Project Management Institute.

The origins of CPM: a personal history. PM Network, 3(2), 7–22. Kelley, J. E., Walker, M. R., & Sayer, J. S. (1989)

Critical-Path Planning and Scheduling, 1959, James E. Kelly & Morgan R. Walker