The Myth of the Triple Constraint

At its heart, successful project management requires softer skills such as communication and persuasion. This why the few more mathematical elements that do exist within project management receive such attention, from estimation techniques to Gantt charting and the triple constraint. However, unfortunately the triple constraint is more of an optical illusion than an effective representation of the project management trade-offs.

Let’s start with cost. The triple constraint is inconsistent with Frederick Brooks’ insights. If you add money to a project, you are more likely than not going to have to add people. Those people will need training and expand the communication nexus across the project team exponentially. This additional training and communication will slow things down, at least in the short term.This is the opposite of what the triangle supposes. So you cannot seamlessly flex the budget to ensure you hit your project goals.

Next scope, the problem here is representing scope as a continuum, where you can chip away or incrementally add work items to the project to flex schedule and cost to the right values. This approach works until it doesn’t. Project success is often binary rather than a continuum. The iPhone 4′s reception problems or the Deepwater Horizon rig show that only up to a point can scope scale up and down before the project hits major risks. In fact, the baggage system at Denver Airport shows that the scope of some projects are infeasible regardless of cost or time.

That leaves schedule as the one corner of the project triangle that can legitimately flex, perhaps this accounts for why most projects finish late. The other corners of the triangle aren’t as malleable as they seem.

5 responses to “The Myth of the Triple Constraint

  1. I don’t think the assertion that there is a triple constraint implies that the relationships are linear… only that they exist.

    I find the triple constraint a useful model for both teasing out risks and potential optimizations. It is also a helpful mnemonic for thinking about the implications of change. I’m open to a different way to represent the concept, but remember the golden rule of models: they are always flawed, and sometimes useful.

  2. The Project Triangle is used as a very poor analogy in modern project management. It doesn’t repesent the nature of the project, it actually represents how you, as a project manager can direct your resources. If you want to place your effort into improving the Schedule , you will not be able to put the same effort into Cost and Scope. Whether the effort you put in pays off and the proejct does get an improvement on Schedule is a very much more complex problem not represented at all well by the Project Triangle.

  3. I think a fourth dimension – benefits – is missing. If scope = requirements then benefits is what the customer / user ultimately gets out of the project or programme. There can always be tradeoffs in this area.

  4. I used to love this triangle becuase it allowed me to win arguements with my customers. Now I hate it. It encourages a strait jacket mentality and turns the solution to every problem into a request for more money or time or both. I think the triangle is a crutch for poor project management.

  5. Pingback: Three myths of project management | Strategic PPM

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