Is the longest path necessarily the critical path of the project?  Case Study

Is the longest path necessarily the critical path of the project? Case Study

PROJECT MANAGEMENT

I was assigned a tower project – 5 basement levels with 17 floors above. They are subject to a schedule! There is no need to devise it – it must only be examined according to the HCP method.

The project schedule consisted of 1,100 tasks and completion was planned within 600 workdays.

The Network Diagram view in MS Project displays the project tasks on 40 A-4 sheets, as follows:

Is the longest path necessarily the critical path of the project? Case Study

PROJECT MANAGEMENT SAAS: CASE STUDY

HCP-Go SaaS (Software as a service), maps the project by paths. A path is a sequence of project tasks from start to finish, interrelated by their logical links.

If the project covers 600 workdays, HCP-Go sees and defines all of the paths that require 80%-100% of the project duration.

Why?

Pareto.

According to Pareto – 80% of the issues will appear in 20% of the paths. What are these paths? Let’s begin with those whose buffer from project duration is up to 20%.

In other words, when managing the project – if our project duration is 600 days, we will seek the paths whose DS (Duration Slack) is up to 20% of the project’s duration, i.e. up to 120 days. In other words – we will seek all of the critical paths that require 480-600 workdays.

When mapping the paths, we found over 50,000(!) paths whose duration is 480-600 days! 

This means 50,000 different paths, i.e. 50,000 different processes that must be executed in order to successfully complete the project, all of which must converge on time and, of course, within the budget…

50,000 paths – that’s a lot more noise than efficacy. It does a project manager no good to be “drowned” in information.

Refining this information, where we have over 50,000 paths, HCP-Go automatically reduces the range in which it seeks paths. It will search for paths with duration-slack within 10% of the project duration, i.e. 600*0.1 = 60 workdays only. In other words – we will seek all of the critical paths that require 540-600 workdays.

Question: How many such paths do you think were found in the project?

Just a minute before you discover the answer by hovering over it with your mouse, try to guess – how many paths do you think were found?

The answer:

That’s crazy too!

So I have decided to further reduce the range, manually. That can be done in the third stage of HCP-Go. Enter the Duration Slack in which you want to find paths – here’s the arrow:

Is the longest path necessarily the critical path of the project? Case Study

I chose a 5% DS. More precisely, 600*0.5 = 30 workdays only!!! 30 workdays are just 1.5 months (assuming a 5-day work week).

Question: How many paths do you think we found?

To see the answer, hover over it with the mouse.

The answer:

The answer:

Insane?

That’s a lot, but it’s a number that we can “work with”.

What’s in the HCP report?

To explain that, here’s an example to simplify matters:

The schedule had two paths – one, critical by HCP (Summary Task #1) and the other, critical by CPM:

Is the longest path necessarily the critical path of the project? Case Study

Question: How can I know all of the technical rules? Isn’t there something that can check the technical aspects for me?

Answer: Today we have HCP-Go, HCP’s Project SaaS. With one click, you can analyze your schedule file – and get a free report with your results!

Examining the tasks in both summaries, we find that:

Tasks A in both summaries require identical durations (1 day).

Tasks B in both summaries require identical durations (2 days).

Tasks C, D and E are also of identical duration in both summaries (3,1 and 2 days, respectively).

But, in Summary Task #1, Task F requires 2 days and only 1 day in Summary Task #2.

Wait, what?🤨

How can a task, critical on CPM, have a shorter duration than tasks on the critical path according to HCP?!

The answer is in the links!


In Summary Task #2 (CPM), the link between Task E and Task F includes a delay of 2 days. This delay leads to the later completion date, thus it is a critical path according to CPM.
However – the path in which we will invest the most work is the one in Summary Task #1 and, as such, it is the critical path according to HCP.

That simple example was detected in the tower project Gantt chart. In other words, within the 1,500 critical paths according to HCP and the hidden paths – more workdays were dedicated to the critical paths according to HCP than to those considered critical by CPM.

What did I recommend the project manager on behalf of the contractor and the project manager on behalf of the entrepreneur?

My recommendation was to focus managerial attention on critical paths according to CPM, critical paths according to HCP and hidden critical paths according to HCP.

Managerial attention” to all tasks involved in the creation of these paths means:

  1. Ensuring that the tasks begin.
  2. Ensuring that the tasks end.
  3. Ensuring that all of the necessary resources are available and usable.
  4. Examining all of the risks related to the said activities, in all aspects: execution, financial, schedule and other risks (such as the impact of various external factors).

And… That’s it.😊

From there on, they knew how to “run” and execute the project on their own.

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