What is Critical Path?
The critical path is the path of sequential tasks on a project that, collectively, takes the longest time to complete.
A project typically has lots of tasks. Some are flexible in terms of scheduling and can be done at any time between two set dates. Others cannot start until a previous task is finished.
There may be two (or more) pathways running through a project — or through part of it — each made up of a string of sequential tasks. The critical path is the pathway that takes the longest time to complete.
A project activity not on the critical path still has fixed start and finish dates (if not the start and finish dates of the project overall), but it can be completed in parallel with other activities, including those on the critical path. The spare time created by scheduling non-dependent activities is called float. It means the Project Manager can schedule that activity at any time between its set start and finish points. This enables resources to be used more efficiently.
Any change to the timing of a critical path activity will change the date by when the project is completed. Shortening it means the next sequential task can be started sooner. Lengthening it has a converse effect.
A Project Manager can, in the event of deliberate or unforeseen change to the timing of critical path activities, make compensating adjustments:
- If a project completion will be delayed by a delay in a critical path activity, a manager might direct extra resources to that activity to save time.
- If a project will be produced ahead of time by a reduction in the timing of a critical path activity, the saved time (or float) may see project resources directed to another task. Or the project overall may simply be finished ahead of time.
Critical path analysis
The method used to manage critical path is called Critical Path Analysis. The computer program PERT (Program Evaluation and Review Technique) is another equivalent management tool. These tools enable managers to plot a project’s tasks (and the time it will take to complete each), as well as their dependencies (meaning: activity B can’t start until activity A is finished, but activities D and E can be done any time between activities B and H). The project’s critical path is then revealed.
For a very informative audio visual display of the principles of critical path, view (and listen to):