AOA, Activity On the Arrow. Explain this type of network diagramming method

Activity on the Arrow (AOA) or Arrow Diagramming Method is drawn with the help of circles and arrows. Circles or nodes represent the beginning and ending points of the tasks (or arrows) while the arrows represent the tasks.

There are various advantages of using Activity on Arrow network diagramming method. Some of them are listed below:

• Each activity arrow has its distinct beginning and end node.
• It is suitable for analytical techniques and optimization formulas.
• It is very easy to view interdependencies of the task.
• The events are numbered so path tracking becomes easy.
• If there are more and more task dependencies then it is easier to draw AOA compared to AON (Activity On Nodes).
• It is easy to estimate the time of the task by viewing the AOA diagram as the length of the arrow depends on the task time.
• Milestone and key events can be easily identified.

There are some shortcomings also of this network diagramming, which are given below:

• The network diagram is not unique as it is in AON diagram.
• Its construction is difficult due to dummy (dummy activities do not have any duration but just show dependencies) arrows and implicit precedence relations.
• It can only show finish to start relations and it is not possible to show lead or lag time.
• It is not supported by many software tools.

The use (help) of ADM or AOA is for scheduling activities in a project plan. It can be described in three steps:

• Drawing of the activity flow.
• Describing the sequence between activities
• Describe all the dependicies between the activities.

The activities are scheduled using diagram consisting of nodes and arrows. A node is the starting pointing which is followed by an arrow (arrow represents the task), length of which is determined by the duration of task, and then arrow is followed by another node. This is one complete task and another task cannot be started if one task doesn’t end.