2.8.1 A case study
Figure 18 shows part of a critical path for converting surplus retail space into a warehouse. Each task is represented by an arrow; the length of an arrow does not relate to the duration of the task. The junctions (called nodes) where arrows meet would normally be numbered. You may come across other formats which use slightly different terms from those we have used.
The numbers on the arrows represent the number of working days it will take to complete each task. As you can see, there is one critical path highlighted. This is because each of the critical tasks depends on the completion of the previous task before it can start. If you add up the number of days for these tasks (2 + 20 + 10), you will see that stock cannot be received until 32 working days have elapsed. Only by changing the timescales for the highlighted tasks can the overall timescale be reduced. Gaining time on other tasks will not affect the calculation.
Box 6: Network analysis: Some key points to bear in mind
Some tasks depend on the completion of other tasks to enable them to start.
A string of such tasks makes a path through your plan, and that path has a very significant effect on the timescale for your project.
The path will tend to define the shortest feasible timescale for the accomplishment of the project, irrespective of the tasks elsewhere.