Project Practitioners > Is It The Triple Constraints or Quadruple Constraints?

Is It The Triple Constraints or Quadruple Constraints?

By Morley Selver, P.Eng IPMA B

If you are working in project management you have probably heard of the Project Management  Triangle or the Triple Constraints. The constraints being scope, schedule, and budget. When managing the project, if one changes we have to look at the other two and see if they change as well. If they have changed then we have to perform some type of control to get the project back in line.

My career has been in industry and I am used to the Quadruple or Four Constraints which is more applicable. The four constraints are Scope, Schedule, Budget, and Resources (SSBR) as shown below:

The Resources can be; money, material, equipment, or people. The SSBR works the same way as the Triple Constraints, i.e. if one constraint changes, you have to look at the other ones to see how they are affected. For example, if there is a change in scope, you have to see what of the other three constraints has changed and write change notices to get the SSBR constraints back in balance. Below I will look at some examples of changes and how they can affect the balance.

You Can't Have That Amount Of Money!

If you have managed projects in industry you know there are always funding issues and spending plans. On a recent project we were installing 14 emergency generators in a refinery. We had the SSBR in balance and put together the funding application for $6 million. This went to management for approval. As they were having spending issues with their capital budget, they looked at what we wanted, considered the risks involved, what their spending plan was, and said no you can't have $6 million we will only give you $3 million. So the funding amount changed and we had to go back and redo our scope, schedule, and budgets to get them all in balance with the $3 million funding. We had this in balance and were merrily working away when near the end of the year they decided we had to spend more money to help meet their spending goals by year end. So, it was adjust the scope, schedule, and budgets to meet the new spending requirements. In both these cases, change notices were written in order to get the SSBR back in balance and carry out the project controls function.

I'm Sorry We Won't Be Able To Make The Delivery Date!

I'm sure you have worked on projects where deliveries of material or equipment have been delayed. When this happens you have to back and look at the scope, schedule and budget. It is usually the schedule and budget that needs to be changed in order to get the SSBR back in balance. This is why it is important to purchase long lead items well in advance and to carry out adequate expediting. Expediting is important and has to be done properly. Most procurement groups will phone the vendor to see if he is on schedule. They keep getting a positive response until about a week before it is supposed to ship when you finally find out it will be delayed. The proper way to expedite is to go visit the vendor / manufacturer and see for yourself what is going on and will they meet schedule. You can always hire inspectors to go visit vendors/manufacturers for you.

You're Too Late And They Are All On Another Project!

The availability of people can have a big affect on the SSBR balance. In a design office you can go to a design lead, tell him that you will have project funding in 3 weeks and you will need 5 designers. No problem is the reply. As usual the funding doesn't come through for 6 weeks. When you go to get your designers, you are told they are working on other projects, and you can only have two. Now what? It's back to checking the SSBR balance and either extending the schedule or cutting scope. The same applies with construction personnel. Are the required number of resources available? This is one of the reasons we look for resource loaded schedules and adjust the SSBR accordingly.

And The Answer Is?

It is for these reasons that I use the four constraints rather than the triple constraints. One of the reasons projects get in trouble is project managers forget the SSBR has to be balanced all the time. If you are in a meeting with Operations and they keep adding scope, you have to know that your costs, schedule, and resource requirements are going up. You can not forget this SSBR relationship. You ignore the relationship at your peril?



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