Critical Path

The critical path represents a task (or a series of tasks) that must be finished on time in order for the task plan to be finished on time. The critical path is based on the longest possible sequence of tasks, factoring in their start dates, finish dates, dependencies, and constraints. It compares the calculated finish date of the last task in the sequence to the planned finish date for the task plan.

The critical path is shown in red in a task plan. Any task on the critical path is a critical task. When a critical task is delayed, it nearly always results in a comparable delay to the finish date of the task plan. A task plan can only be considered 100% complete when the last task in the critical path is finished.

As you are working in a task plan, you should pay close attention to the tasks that are part of the critical path and should work to ensure that they are completed on time (and without causing delays to other tasks or to the task plan). For each critical task, verify that the resources assigned (or allocated) to the task are not only the right resources, but that there are enough of them. For example, replacing a less experienced resource with one who has more experience may be what is needed to ensure that the task is finished on time; however, don't forget that adding a resource who is unfamiliar with the task may require ramp-up time that the schedule does not have room for. Try to find slack in the task plan. Once slack is identified, you can determine whether any tasks can be given an earlier start time, a later finish time, and so on, so that any negative slack is removed and any available slack is used to your advantage. Verify constraints. For example, an inflexible constraint puts pressure on the overall task plan because a task with an inflexible constraint must start (or finish) on a fixed date. Though it is not always possible, you should work to avoid having tasks on the critical path that have inflexible constraints.