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Iron Triangle of Project Management

Instructor: Bob Bruner

Bob is a software professional with 24 years in the industry. He has a bachelor's degree in Geology, and also has extensive experience in the Oil and Gas industry.

Project management often requires a balancing act between key factors that constrain the overall project delivery. In this lesson, we review the concept of the iron triangle of project management as a means of maintaining that balance.

Understanding Your Project

Imagine you are heading in to a meeting with upper management to review a project you're managing. The project has already had to slip its schedule and is running over its budgeted costs. Your co-workers seem worried, but you have all the information you need, and you head into the meeting feeling calm and collected. Most importantly, you have a working knowledge of the iron triangle of project management to describe the current situation. Let's review how this project management concept can lead to a successful outcome in your meeting.

The Iron Triangle Defined

Two other terms often used to refer to the iron triangle of project management, triple constraint and flexibility matrix, can help us better define this concept.

The 'constraint' in the term triple constraint refers to the basic factors that need to be accounted for during planning and delivery of any project. These three factors are the well-known attributes of scope, schedule, and cost. Scope refers to the total amount of work involved in delivering the project, cost refers to the sum of all resources required to deliver that work, and schedule reflects the time estimated or allotted to the project's delivery. And the word 'flexibility' in the term flexibility matrix indicates that these three factors can, and should be, linked together.

The basic premise of the iron triangle is that if you are required to make a change in one of these areas, at least one of the other constraint points will also need to change to balance the overall effect. This relationship is often pictured in the form of a triangle, with dynamic links between each of the constraint attributes that sit at each vertex.

Iron Triangle

The Iron Triangle in Action

We can go back to our initial example to see how this concept can be used to help resolve any issues that arise as a project moves forward. In our hypothetical case, let's assume that one of your sales staff promised something to a key client that was not in the original plan. At the time that change in scope was made, which would likely have been done through a change request, nothing was removed to account for the addition of the new feature. To avoid problems with project, it would have been necessary to change either the schedule or cost estimates to account for the alteration to the initial plan. The overall project is constrained by these three factors in such a way that changes in one area must be reflected by changes to the plan in another area, or the project will go out of bounds.

The notion of flexibility can also be applied to help guide the best way to react in these types of situations. At the start of any project, it is useful to agree on which of the three factors is the easiest to change and which is the most difficult to change. For example, a firm schedule commitment that includes associated penalties for any delayed delivery will probably mean that schedule is considered the least flexible component. If cost has been designated as the most flexible component in your delivery, you might move to keep the project on schedule by working extra hours that incur an additional resource cost. Or if the overall scope is actually the most flexible constraint, you would first look to remove some of the lowest priority scope items in order to keep the schedule in bounds.

Other Constraint Considerations

The constraints discussed in this model are typically measured against an overall project plan, and adjusted accordingly. For example, budget is a constraint term that is often used in place of cost, since this term more accurately reflects the planned costs that were used to form the project baseline. In the same vein, personnel resources often make up the bulk of a project's total cost structure. When combined with the fact that personnel resources may need to be shared across projects, then using resource as one of the key constraint points may be more beneficial in understanding the relationship between key constraint factors.

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