Critical Path Method (CPM) Analysis Expert Overview

In this article, civil engineer, Michael D. Klein, P.E., CHMM, provides an introduction to the most widely accepted method for evaluating project delay/disruption claims, the Critical Path Method (CPM).

CPM Analysis of Schedule Delay & Disruption

The most widely accepted method for evaluating project delay/disruption claims is the Critical Path Method (CPM). The CPM is a mathematically based algorithm for scheduling a set of project activities.

A CPM schedule analysis can establish:

• The longest path of planned activities to the end of the project
• The earliest and latest that each activity can start and finish without delaying/disrupting the project

A schedule using CPM can help you determine:

• How long a complex project will take to complete
• Which activities are “critical,” meaning they must be completed on schedule, or else the entire project will take longer

CPM can also account for the resources related to each activity in the project. By utilizing processes called activity-based resource assignments and resource leveling, it is possible to estimate the cost of each activity and the costs associated to accelerate each activity.

CPM can help determine:

• Whether or not it is cost effective to accelerate a project, and, if so,
• What is the least costly approach

There are numerous ways to approach a schedule delay analysis. The methods selected are often a function of the type of claim and the documentation available from which to develop the analysis. The approaches to schedule delay analysis all share a common theme; they are after-the-fact, based on a combination of historical data, assumptions and estimates.

Definitions:

Float (slack) - amount of time that a task can be delayed without causing a delay to:

• subsequent tasks (free float)
• project completion date (total float)

Critical path - the sequence of activities which add up to the longest overall duration. It is the shortest time possible to complete the project. Any delay of an activity on the critical path directly impacts the planned project completion date.

Critical activity – activity with zero float

Resource leveling – iterative process of assigning crews to activities in order to calculate their duration

Featured Expert

Michael D. Klein, P.E., CHMM, C.F.E.I.

Civil Engineer & Environmental Expert

Michael is a Civil Engineer (MSCE) with over 25 years of experience in the design, planning, and delivery of high-value projects for both the government and private sector. He combines his engineering… read more.