How to use network diagrams in project management

How to use network diagrams in project management

This post was originally published on September 6, 2019, and updated most recently on July 25, 2020.

When it comes to projects, the bigger it is, the more complex the management process becomes. There are tasks to plan, schedules to organize, and dependencies to juggle. In short, it’s a handful. This is where a network diagram project management approach comes in handy.

When thinking about network diagrams, most people think of something that depicts a telecommunication network. But rather than illustrating a physical network of servers and firewalls, they can also depict how one task in a project connects to another task — something that’s incredibly useful for managers.

Research shows that presenting information visually can help improve understanding and enhance retention, which is especially useful when dealing with lots of data. Because network diagrams show every task and dependency in one go, they can help project managers estimate jobs, make more informed decisions, and track and manage progress more efficiently.

What are the different types of network diagram?

There are a plethora of different types of network diagrams, but when it comes to project management. But, there are only two you need to know: the Arrow Diagram Method (ADM) and the Precedence Diagram Method (PDM). One you’re familiar with them, you can put together a net diagram template for your own system.

Arrow Diagram Method (ADM)

The ADM does what it says on the tin: it uses arrows to illustrate different activities. The beauty of this option is that it’s incredibly intuitive. The tail of the arrow extrudes from a box (sometimes referred to as an ‘i-node’) that represents the starting point of a task. The head of the arrow points towards another box (sometimes referred to as a ‘j-node’) that represents the end or finish point. The length of the arrow itself denotes the amount of time spent on the activity (so long arrow = long task, short arrow = small task).

The relationship between nodes can only ever be ‘start-to-finish’ (SF) although sometimes, ‘dummy activities’ are used to show dependencies. These are usually used in a ‘finish-to-start’ (FS) situation. To use an analogy: icing a cake (task C) can’t begin until the cake has been made (task A) and the icing mixture has been prepared (task B). So icing is connected to the other two activities (A and B), but they’re not connected to each other. In this instance, you’d need to draw a dummy activity between A and B. This dummy shows that you need to complete A and B in order to complete C.

Pros: This type of diagram is simple to create and understand, with no formal training required.

Cons: There’s no way to include lead and lag times without adding new elements into the diagram. This means it’s a little simplistic for many project managers.

Precedence Diagram Method (PDM)

The PDM method is like a souped-up version of the ADM. You still have boxes and arrows. But instead of the arrows representing a restrictive ‘start-to-finish’ relationship, they illustrate four possible relationships, including:

  • Finish-to-start (FS): This is the most common type of relationship. It occurs when one task can’t begin until you complete another. For example, you can’t ice the cake until after you bake it.
  • Start-to-finish (SF): This refers to a situation where one task can’t begin until the other starts. For example, the implementation of a new project management software system has to begin before you can turn off the old system.
  • Start-to-start (SS): This refers to a situation where the second task can only begin once the first task has begun. Both activities can begin simultaneously, although they don’t have to begin at the exact same time. To go back to the cake analogy, to make the most efficient use of your time, you’ll want to use the time when the cake is in the oven to do something useful – like make the icing. So in this instance, ‘bake cake’ and ‘make icing’ are a start-to-start relationship.
  • Finish-to-finish (FF): This refers to a situation where the completion of one task relies on the completion of another task. The second task can finish simultaneously, or any time after the first task is complete. To use the cake analogy again, say candles are the finishing touch to your cake decoration. Before you complete this task, you need to deliver the goods. In this case, finishing the decoration depends on you finishing the delivery.

This method is useful for tracking lead times (the amount of time you have to finish something before it impacts the next task) and lag times (delay times) alongside the arrows. This gives the project manager a clearer idea of scheduling and scope, which helps with reporting and managing the team.

Pros: You can more accurately estimate time and make more informed decisions based on a deeper knowledge of each dependency. This means you can make adjustments without sending your project off-track. And if anyone asks you to justify your estimates, you’ll have a detailed, logical representation of your timeline.

You can also use this type of diagram to discover opportunities for optimization both during the project and afterward. Review the diagram in your post-mortem meeting as a learning tool for better project management.

Cons: This type of diagram understandably takes longer to create than the simple arrow method, but, as you’ve probably guessed, the extra time it takes more than pays off in the long-term because you have more accurate, detailed information to work with.

Final thoughts

Whatever your project, creating a network diagram can help you understand the relationships between tasks far more easily.

Investing in a quality diagramming tool to help you create your network diagrams is a must: not only will you be able to draft them quickly with the help of pre-made templates and shapes, but you’ll also be able to share them with your team easily, especially if you choose a cloud-based solution. Like the tasks in a network diagram, your role doesn’t exist in isolation; the more you collaborate with your team, the better your chances of completing everything right the first time.

Georgina Guthrie Georgina is a displaced Brit currently working in France as a freelance copywriter. Before moving to sunnier climates, she worked as a B2B agency writer in Bristol, England, which is also where she was born. In her spare time, she enjoys old films and cooking (badly).