Activity Network Diagram (AND)

Introduction: Activity Network Diagram (AND)

An Activity Network Diagram (AND) is a project management tool that shows the sequence and dependencies of tasks in a project. It helps teams understand the order of activities, identify the critical path, and plan timelines effectively.

Background

The AND is one of the Seven Management and Planning Tools, developed to improve planning and control in complex projects. It is closely related to methods like PERT (Programme Evaluation and Review Technique) and CPM (Critical Path Method), widely used in project management.

Key Elements / Features

• Activities – Each task in a project is represented by a box or node.
• Arrows – Show the sequence and dependency between tasks.
• Start and finish points – Define the boundaries of the project.
• Critical path – The longest chain of dependent tasks, showing the minimum time required to complete the project.
• Slack or float – Flexibility in non-critical tasks.

Applications / Examples

• Project planning – Mapping the sequence of tasks in construction, IT, or product development.
• Process improvement – Showing dependencies in Lean initiatives.
• Event planning – Organising timelines for conferences or training programmes.

For example, in a software project, an AND might show that coding cannot start until the design is finished, and testing cannot begin until coding is complete. This visualisation makes delays easier to predict and manage.

Relevance / Impact

An Activity Network Diagram improves project reliability and efficiency. By making dependencies visible, it helps managers allocate resources, avoid bottlenecks, and focus on tasks that drive project success. It is a key tool for structured project management and Lean planning.

See also

• Process Decision Program Chart (PDPC)
• Tree Diagram
• DMAIC
• Critical Path Method (CPM)