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Flaws with the Iron Triangle Skip to main content

Flaws with the Iron Triangle

This post provides a perspective on the risks of output-focused project management and specifically identifies flaws with the iron triangle or triple constraint. This is part of a series to improve awareness of sustainable change delivery.

“The systems that fail are those that rely on the permanency of human nature, and not on its growth and development” – Oscar Wilde.

This is an extension of the post, ‘A Project Manager’s True Purpose: Output, Benefits or Both?’ As previously mentioned, some approaches to project management focus on short-term output, as opposed to long-term benefits. The output perspective tends to focus almost exclusively on project output, including factors like time, cost, scope and the project team, with minimal focus on the organization and its operations.  Though a key foundation and construct for the project management discipline, it relies on further building blocks to deal with the evolution of project management.

The iron triangle often leads to the constraints perspective of pick only two:

“You are given the options of Fast, Good, and Cheap, and told to pick any two. Here Fast refers to the time required to deliver the product, Good is the quality of the final product, and Cheap refers to the total cost of designing and building the product. This triangle reflects the fact that the three properties of a project are interrelated, and it is not possible to optimize all three – one will always suffer. In other words you have three options:

  • Design something quickly and to a high standard, but then it will not be cheap.
  • Design something quickly and cheaply, but it will not be of high quality.
  • Design something with high quality and cheaply, but it will take a relatively long time.” (Wikipedia, “Project management triangle”, 2015)


    Exhibit 1: “Pick any two” (Wikipedia, “Project management triangle”, 2015)

As highlighted below in exhibit 2, the iron triangle output focused model follows production management theory from an insightful presentation by Greg Usher entitled, ‘Rethinking Project Management Theory’, presented at the second International Project Management Association (IPMA) Research Conference 2014 in Tianjin, China.

Exhibit 2 presents an interesting comparison between production management theory and output-focused project management approaches that follow similar assumptions.

Exhibit 2: Underlying Assumptions about Production Management Theory (Usher, p8, 2015).


Exhibit 2 also demonstrates that production management theory and some project management approaches have a very structured and process-focused method for output.

Exhibit 3 was taken from figure 4.3 of the Office of Government Commerce’s Management of Risk methodology. This figure highlights the process model and reinforces the tasks, input, process goals and process steps leading to the output. This approach is very waterfall in its execution.

Exhibit 3: Process Model ((OGC – Management of Risk, p. 31, 2012)).


A description of the elements listed in exhibit 3 are outlined below:

  • “Goals
    • are the key outcomes of the process. For instance, the process goal for the identify step is to identify both the threats and opportunities facing the activity under examination as comprehensively as possible.
  • Inputs
    • describe the information that is transformed by the process. The absence of appropriate inputs may prevent a process from taking place effectively. Partially completed inputs may enable a process to be completed but in many instances would require a process to be repeated when more complete information was available.
  • Outputs
    • describe the information produced by the process, which will form the inputs to the subsequent process step.
  • Techniques
    • describe the recognized risk management tools and techniques that may be applied to the process step to help create the outputs. Some techniques are useful in more than one step but they are described in this chapter only once, in the step where they are used first.
  • Tasks
    • are the actions that need to be completed to transform the inputs into the outputs with the aid of the techniques” (OGC – Management of Risk, p. 30, 2012).


Exhibit 4 identifies how time, quality and cost are based on production theory.  This shows that there is also an association with output-focused project management and the focus on the iron triangle of time, cost and quality/scope.

Exhibit 4: Transformational Views of Production Management: Objectives (Usher, p. 5, 2014).

Exhibit 5 shows the underlying principles and foundational theories that are common to production management and certain project approaches.

Exhibit 5: Foundational Theories of Production Management: Underlying Principles (Usher, p. 5, 2014).

Though acceptable in simple and straightforward engagements, projects by their very definition are unique and dynamic, requiring more tailored, organic approaches.

Challenges with the Iron Triangle Focus

Unfortunately, a process focus within change delivery can lead to organizations following a colour by numbers approach to project management.

Exhibit 6: Colouring by numbers does not guarantee success.

In general, change delivery frameworks, standards, methodologies and processes all state that each situation must be tailored to current conditions and should be based on experience. This is particularly important for projects that are complex and undergo a great deal of change.

‘. . . no plan of operations extends with any certainty beyond the first contact with the main hostile force’ – Helmuth Karl Bernhard Graf von Moltke, 1871, ‘On Strategy’.

This is often paraphrased as, ‘No plan survives contact with the enemy’ (Barnett, p. 35, 1963).  In short, managing all projects using a controlled production process with pre-defined requirements, inputs and tasks leading to a predefined output with nominal change is unrealistic.  Even PRINCE2 (PRojects IN a Controlled Environment) presumes a changing and dynamic environment. One of the PRINCE2 themes, aspects of project management that must be continually addressed, includes change. PRINCE2 is not an output-focused methodology.

‘The purpose of the change theme is to identify, assess and control any potential and approved changes to the baseline. . .

Change is inevitable during the life of a project, and every project needs a systematic approach to the identification, assessment and control of issues that may result in change’ (OGC – PRINCE2, p. 91, 2009).

GPM Global argues that project management maturity follows the transition outlined below in exhibit 7.  The focus on output may be acceptable when starting out on simpler projects.  With more complex projects, the attention should progressively evolve to include a benefits and organizational focus.  The next evolution is the acceptance, adoption and integration of sustainability into the project management life-cycle, as outlined below in exhibit 7.

Exhibit 7: The Evolution of Project Management



This post has outlined the challenges of an output or iron triangle focus in project management.  It has also shown the alignment between output focus and production theory, which is not ideal for a strategically important and dynamic change delivery environment.  If you are still in the early stages of project management, please consider reviewing some other approaches.


Series Objectives

This series is all about raising awareness of sustainable change delivery and the integral elements, disciplines and competencies associated with it. In the graphic below, each of these elements is identified in terms of its use in allowing for sustainability. These elements form the basis of the GPM® Global’s P5™ Standard for Sustainability in Project Management, the GPM® Global Training Programs and the GPM® Global Portfolio, Program and Project Sustainability Model (PSM3™) for organizational assessment.

Exhibit 8: Organizational Sustainable Change Delivery Elements and Disciplines / Competencies


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APM (2012). Delivering Benefits from Investments in Change: Beyond ‘Business as Usual’ to ‘Value as Usual’.

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Peter Milsom

Peter Milsom is an entrepreneurial advocate for sensible, sustainable change delivery practice. Peter has come to realize that sustainability is the perfect catalyst for Project / Programme / Portfolio / Risk / Value / Business Case and Benefits Management improvement. As an entrepreneurial methodologist Peter's unique value proposition is the vast array of tools and techniques that he brings to every engagement using the most cost effective and efficient methods based on the situation and tailored to meet your needs. This is based on his unique combination of experience and extensive training / certifications in change delivery, value / risk / benefits management business case, and business architecture.

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