Network Diagram in Project Management?

What Is a Network Diagram in Project Management?

A project network diagram is a visual representation of the workflow of a project. A network diagram is a project management chart that is populated with boxes noting tasks and responsibilities, and then arrows that map the schedule and the sequence that the work must be completed. Therefore, the project network diagram is a way to visually follow the progress of each phase of the project life cycle to its completion.

Project managers use a network diagram to track the project schedule network, allowing them to see the progress of each activity. Then they can share the status with the rest of the project management team. This is especially helpful for those who better understand information that is delivered visually. For those team members, project network diagrams will help with the performance of their tasks and increase the project’s productivity.

Another aspect of the network diagram is that it literally illustrates the project’s scope. That’s because the project network diagram collects all the activities, milestones and deliverables defined on the work breakdown structure of the project. The Critical Path Method (CPM) and the Program Evaluation and Review Technique (PERT) are good examples of how to use network diagrams in project management. Project managers use these methods to estimate the duration of the project and create a project schedule.

Types of Project Network Diagrams: ADM & PDM

Project network diagrams can be divided into two types, the arrow diagram method (ADM) and the precedence diagram method (PDM). The main difference between an ADM and a PDM project network diagram is the way they represent tasks and milestones.

As expected, the arrow diagramming method uses arrows to represent the project activities, with the tail of the arrow being its start and the point the finish. The length of the arrow is the duration of the activity. The arrows connect nodes or boxes that are milestone symbols of the start and finish of the activity in sequence.

In the precedence diagram method, each node or box is an activity. There are arrows, but in this case, they represent task dependencies. There are four types of task dependencies:

• Finish to start: This means an activity cannot start before its predecessor is finished.
• Start to start: Use this when two activities can begin simultaneously.
• Finish to finish: Use this when activities must finish together.
• Start to finish: Use this when one activity cannot finish until another one starts.

Project Network Diagram Examples

Here are two project network diagram examples to help you understand how they’re used in project management. They illustrate the two main types of project network diagrams. We recommend creating a work breakdown structure in both cases.

1. Critical Path Diagram

Here’s a simple project network diagram example created to identify the critical path of a project. It’s a precedence diagram, so the green letters highlight the critical path activities, while arrows indicate task dependencies.

2. PERT Chart Network Diagram

PERT charts are a type of project network diagram that represents tasks, dependencies and their start and end date. As you can see in the image below, this arrow diagramming method also identifies the critical path to estimate the project duration.

How to Make a Project Network Diagram in 3 Steps

First you need to understand the chronological order in which activities need to be executed and define the project network diagram start and end point. When you’re plotting your diagram, use arrows that go from left to right. That’s how people read in the West, and the diagram should intuitively follow that pattern.

You’ll want to make your project network diagrams as clear and easy to discern as possible. That means don’t clutter the page with arrows that cross one another. In fact, any arrows that you use for directional purposes should be straight. But the length of time that an arrow represents shouldn’t be determined by its length.

1. Create a Predecessor Table

A predecessor table is a simple table that lists the activities in one column and notes their preceding tasks in another. Here’s the predecessor table for our PERT chart network diagram example. Remember that this is a predecessor table for an arrow diagramming method, where the arrows represent activities, and nodes represent milestones.

 

2. Identify the Activities for Your Project Network Diagram

Before you even put pencil to paper, you need to organize your tasks. You don’t want to start making your project network diagrams and realize that you’ve left out some important activities. There’s also task dependencies, where tasks can’t start or end until another activity starts or ends. Identify these with a work breakdown structure and break the project into its phases. Then you’re ready to start designing your project network diagram and find out the critical path.

3. Make a Rough Draft of Your Diagram

On a more basic level, start your project network diagram by penciling it out first. You can then erase and move items around until you’ve designed the most effective schedule network diagram.