Project management header
products page

Detailed planning – Critical path - 1

This will be the longest path

By its very nature the critical path contains all of the tasks, which can affect the completion date of the project should their durations, start or end dates alter.
It will be the longest of a group of tasks that follow each other.

When the schedule is viewed via suitable software it is easy for the critical path to be highlighted.
Project control will quite often focus on the critical path.

All tasks have zero float

The critical path is characterised by each task on it having zero float.
Sometimes this is also referred as slack which is not quite the same.


The float between two Tasks ‘A’ and ‘B’ is the amount of time Task ‘A’ can be delayed before it has a detrimental effect on the start or end point of Task ‘B’.
In its simplest form for a finish-to-start relationship, there may be two weeks after the completion of Task ‘A’ and the start of Task ‘B’, and Task ‘B’ requires Task ‘A’ to finish.
The float is therefore two weeks.
If Task ‘A’ is held up for three weeks then Task ‘B’ will be delayed by one week.

In addition there is a subtle difference between ‘float’ and ‘slack’.
They often used in the same context.

It is very common for people to use the word ‘slack’ instead of float.
Slack really only applies to Activity-on-Arrow networks and the events that are created.
These show arrows that represent tasks and start and end at ‘events’.
It is only these ‘events’ that can have ‘slack’.
Only the tasks themselves have ‘float’.
However, for most times they will be one and the same.

For the critical path ‘slack’ and ‘float’ will be the same that is, zero.

Don’t have more than one critical path

It is possible for there to be more than one critical path running in parallel.
As the project management team would like to focus on the critical path having more than one will divert attention and resource priorities.

For better project control it is best to reduce the project schedule to one critical path only.

Do whatever is necessary to keep the critical path activities on track

The project management team must focus effort on keeping the critical path on track.
If this is the case the overall project will remain on track.

The project management team must be wary that in focusing too much effort on the critical path other tasks become poorly controlled and end up on the critical path or affect the current one.

Non - PRINCE2 information