Question

The concept of ‘critical path’ can often be confusing, as many students want to believe that it is the ‘shortest’ path through a network. Convincingly explain why this is not so. Explain how the critical path defines the project’s duration and how “crashing” affects that.

Answer 1

The critical path of a project is the longest path of the project network. It is a path that has 0 buffer or Slack. It is called "Critical path" since it has to be monitored continuously and rigorously and ensure that no delay occurs on that path. Slightest delay on the critical path will delay the entire project proportionately. There is no play to extend any activity on a critical path. Each activity has to be compulsorily completed within the planned time to complete the project on time. The shortest path has a lot of slack. Even if there is a delay on the shortest path, the project will not delay as the duration of the project completion is completely dependent on critical or the longest path.

The duration of the critical path will be the duration of the project as explained above. The shorter paths will be one of those paths in the network that will get completed before the critical path. The critical path will be the last path to be completed in the project.

Crashing reduces the duration of the critical path by adding more resources. If an activity takes 2 days by making 1 resource work, it will take generally 1 day by making 2 resource work. This will help to shorten the critical path. However, adding more resources after planning and start of execution will lead to an increase in actual cost of the project compared to the planned cost. Further, a note has to be taken that while crashing a critical path, other non-critical paths may become critical. In this case, crashing of activities on both the paths have to be carried out simultaneously, in order to reduce project duration. Crashing increases the cost overrun risk in the project.