## Critical Paths

The critical path for a project is that which determines the shortest time in which a project can be completed. It is of greatest value where there are sophisticated network diagrams, involving multiple parallel activities.

The method involves the addition of the earliest start and latest finish time for each activity on the network diagram. Then using the list of precedents it is possible to calculate the shortest time in which the project can be completed.

Adding up the times of each step in the Gantt Chart (Figure D17) of Project X gives a figure for the total time spent on these tasks of 30 months. However, because of overlapping activities the overall time is reduced to 24 months. Looking at the network diagrams in Figure D18 and the earliest start and latest finish dates in the Gantt Chart, it can be seen that F and G are off the critical path. Therefore the critical path follows A, B, C, D, E and H. It is these steps that must be looked at if the critical path and hence the time of the project is to be reduced.

When the times for each project task are very firm a special method, the Critical Path Method (CPM), can be used to ask more sophisticated questions about how to shorten the project time. The types of questions that can be asked are: "what are the benefits to the completion date by adding more manpower to task A or more capital into task B?"