Wednesday 16 February 2022

What is a critical project path, and why is it needed

In continuation of the posts about the basic things in project management - today is a post about such a popular concept as the critical path of the project.

Like everything in project management, the critical path is a simple thing in its genius. If we think of a project as a set of interrelated tasks, then the critical path is the longest chain of sequentially performed tasks from the beginning to the end of the project. Accordingly, if the time of some task NOT from this chain increases, then this will not affect the overall duration of the project. But if the time of any task on the critical path grows at least by a day, the term of the entire project will shift accordingly. That is why this chain is called the critical path.

As you can see, everything is simple – the project manager must know what tasks in his project lie on the critical path and ensure their implementation on time, otherwise the project deadlines will go. That's it. Of course, there are nuances, but more on them below.

How to Build a Critical Project Path

Determining the critical path of the project is very simple:

Make a list of all the works in the project and their duration (here, as you remember, WBS will come in handy). In my favorite example with repairs in the list of works will be: demolition of interior old walls, erecting new ones, plastering, wallpaper gluing, electrical device, water wiring, laying laminate, etc. At this stage, our goal is to get an exhaustive list of works and an understanding of how much each of them will take - we need 3 days for plaster, 10 for electrics, 4 for laminate and so on.
Determine how the works relate to each other.


Well, for example, what is the condition for starting electrical work? 


Perhaps at least the walls erected? There are walls – you can start. And the conditions for gluing wallpaper are already more - this can be started at the very end, when the laminate has already been laid, and the electrics are mounted, and, of course, the walls are plastered and plastered. By the way, there are different types of connections (one work can begin only after the end of another, only simultaneously with another, etc.), but at this stage we will not complicate. You can write this out in Excel or in MS Project, numbering the work and putting next to each of them the numbers of those works, the completion of which is necessary for its start.

Further, the methodology tells us that we need to develop a network diagram - write the numbers of works by hand on a piece of paper in circles, connect them with arrows depending on what work is going on, and write the duration of this work on the included arrows. Well, or not by hand, but in any software (do not close the post, this is for understanding, in life no one in their right mind does it manually, of course!). The finished network graph looks something like this (pictures, as always from Google):

Now we can calculate which chain is the longest and highlight it with color. In the graph below, these are works 1-4-5.

Well, congratulations, you've identified a critical path for the project. Now you know that the project term depends on tasks 1, 4 and 5, they will "go" - the whole project will "go". So, they get all the attention.

When building a network chart, there are many nuances (for example, several duration estimates can be applied to the graph at once - optimistic, realistic and pessimistic, you can use different types of connections, etc.), but if you are reading this post - most likely, you are recently in the profession of a project manager. Therefore, we will not overload the post with details that you will need only after a while (and it is not a fact that you will need it at all). In any case, if you want romantic details - they can always be found in the same PMBOK.

In life, network graphs, of course, no one draws, especially by hand. At best, tasks with dependencies are entered into MS Project, and it builds everything automatically, at worst , they use Excel and do it by hand at the risk of making a mistake. For those who know a lot – you can even find macros on the web that will build everything in Excel for you, but I can't understand why you need this sado-mazo.

Moreover, in 90% of cases, even an experienced project manager will look at a network diagram automatically built in MS Project and ask "what kind of crap is this?", since the Gantt chart has long been the industry standard for representing a critical path.

This is what network diagram looks like in MS Project. Not really, right?

Below will be examples of how the constructed critical path looks in MS Project in the form of a Gantt chart. If you do not have access to MS Project , many free and paid project planners can do the same, you can see more details in the post about the Gantt chart.

Critical Path Examples

I searched in Google, there, as always, a lot of incorrect examples, but still selected several sane in the form of Gantt charts, built using MS Project. To me, this visualization seems the easiest to perceive. As mentioned above, technically in MS Project you can build full-fledged network diagrams, but this is definitely not necessary for beginners (and continuing, let's be honest, very rarely use them).

MS Project automatically highlights tasks on the critical path in red, if you open the desired view, it is very convenient.

Well, cool, it's immediately clear what to focus on!

Also on this topic in the blog there is a link to an excellent video about project management in the USSR, I recommend watching to understand better, since since then nothing much has changed.

Using the Critical Path in Practice
As usual – a few thoughts from practice about common mistakes when using a critical path in projects:

Do not forget about the secondary critical path. 


I wrote above that the project manager should first of all concentrate on the tasks of the critical path, so any project management methodology tells us. Practice does not argue with this, of course, but additionally believes that it is necessary to work with tasks that, when planning a project, seem to lie outside the critical path, but can be on it with a relatively small delay in their implementation. We return to the repair - for example, on the critical path we have pipe wiring in the bathroom - > laying tiles - > installing a bath and toilet. 


Outside the critical path lies the task of "purchasing tiles" and it seems that the repair has just begun, there is still plenty of time, the tiles can be bought back-to-back to the time of its laying (if you strictly follow the methodology). But a good foreman (and a good project manager) when assessing risks immediately see that if something goes wrong and the purchase or delivery is delayed, all the terms of repair of the bathroom will shift. 


Therefore, it is worth starting procurement early, so that this task does not turn into a task on a critical path. This is an example about a specific task, but when evaluating, it may turn out that you form several practically independent chains (for example, the total repair period of the entire apartment is affected by both the repair period in the bathroom and the period of wiring the electrics). On forums or in chat rooms, you can find informal terms "secondary critical path", this is exactly what we are talking about.

Do not calculate the critical path up to the day. 


This point is related to the point above, it happens that when determining a critical path, the difference between several of its variants is literally several days, and a chain is taken as a critical path, which is literally a day or two (or a week or two) larger than the alternative one (again, in strict accordance with the methodology). But the project is a living organism, "exactly as planned" everything passes very, very rarely, so with a small difference, it is better to immediately honestly admit that both chains are your critical path, and give them both increased attention. Otherwise, with a probability close to 100%, this bomb will explode at the most inopportune moment.

Do not think that the critical path is interesting only to the project manager. 


In any more or less experienced project team, all performers know what a critical path is, and that when the project manager says "this task is on a critical path", it means that she has the number one priority. If you are not sure that your team knows this – spend 5 minutes, talk about the concept of the critical path, show what the critical path looks like in your project, what tasks got there, and what you expect from those who will perform them. Honestly, it's worth it, and people will be pleased to learn something new.

Do not assume that the critical path is "carved in stone"..


 In a world with the right methodology, of course, you should have optimized the critical path as much as possible even before the start of the project, but if no one demanded from you to reduce the planned deadlines, then, most likely, you did not strain, right?


It is often possible to see that the project manager himself is stressed and the team brings if something goes wrong on a critical path, but for some reason does not make any attempts to somehow shorten this most critical path in order to "pull out" the previously agreed deadlines. Almost always, if desired, the opportunity for optimization can be found if the eye is already blurred - consult with the neighbor-RM, manager, team, the solution will definitely be found.

Do not leave "floating tasks" in the project. 


In any project, there are tasks that seem to be strongly unrelated to others, and most often they remain just in the list of tasks, rigidly not tied to others (this, by the way, is the case when the methodology is 100% right when it says that ALL tasks should have an input and output, it just does not follow the majority in this matter). As a result, they are forgotten and at the end of the project they shoot like a gun that was standing in the corner. For example, in repair, such a task may be to "seal the meters". 


Well, what can be done at any time of the project, definitely not on the critical path, we will definitely reach the end of the repair. But when throwing between the choice of tiles and the pouring of the floor, everything is somehow not up to it, and it seems that the repair has already been completed, and we have not sealed the meters, a lot of money during this time was wasted, paying for water according to the standards, and even it turned out that the management company had a queue for sealing for 3 months. 


As a result, we cannot close the project, the money literally "drips", in the head you need to continue to keep it all, etc. And you just need to follow a simple rule - any task should be connected with others. It's right in the stone of project management that needs to be carved.

Well, that's probably the whole minimum program about the critical path. I wanted to stuff information into the same post on ways to optimize the critical path, but I realized that this pulls on a separate post, so some other time.

Do you use the critical path method in your projects? Tell us in the comments here or in the telegram!


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