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Manual methods – part 3b – task flow charts

Activity-on-Node networks

The Activity-on-Node networks use the ‘bubbles’ to indicate the task, the start and finish and any other information.
Traditionally, the bubble is expanded to show this other information.

AON bubble diagramAON bubble diagram large
Task number

Shows the task number (#2 in this case) from the work breakdown structure.

Earliest Start Time (EST)

This is the earliest the task (day 4 in this case) could begin bearing in mind it is waiting for a previous task to complete.
This will be zero for all tasks beginning directly after the start.

Earliest Finish Time (EFT)

This is the earliest time the task will complete based upon the Earliest Start Time and the task duration.
The ‘duration’ is 3 days and the Earliest Start Time is day 4 so the Earliest Finish time (EFT) is day 7.

Latest Start Time (LST)

This is the Latest Finish Time (LFT) minus the ‘duration’. In this case, the Latest Finish Time (LFT) is day 9 and the ‘duration’ is 3 days so the Latest Start Time (LST) becomes day 6.
The reason for this may not be immediately obvious but will be explained in a little more detail later.


The number of days estimated the task will take. This will take into account the level of resource attached to the task.
For example, this task may have been judged to take 3 days with three men, who are expected to be available.
If only one man becomes available is will take 9 days.