Define the Arrow Diagramming Method

• Activity-on-Arrow (Branch) with nodes as dependencies
• Uses finish-to-start precedence only. The solution method for an activity on arrow problem is essentially the same as for the activity-on-node problems requiring forward and backward passes to determine the earliest and latest dates.
• May require use of dummy activities to maintain proper logic of various construction activities. If two activities have the same starting and ending events, a dummy node is required to give one activity a uniquely identifiable completion event.
• A dummy is treated as an activity (represented by a dotted line on the arrow network diagram), that indicates that any activity following the dummy cannot be started until the activity or activities preceding the dummy are completed. The dummy activity does not consume time or any resource.
• Review Figure Activity-on-Arrow diagram below. Note the dummy activity showing the relationship between the material procurement and installation of the components.

Diagram- Activity on Arrow Diagram