Dealing with schedule planning by the Critical Path Method
A project usually involves a large amount of activities and tasks needed to be done. Even for the most experienced project managers it can be a bit of a challenge to control the huge amount of complexity in a project. By mastering the concept of planning a schedule a project can not only be more structured. Sufficiently planning can reduce the overall costs and limit the time duration of the project. The Critical Path Method is one of the tools a project manager can use to plan the project in the best possible way.
This article analyses the Critical Path Method. It takes a closer look at how to use the method and discus the advantages and limitations of the method.
The article starts by clarifying the idea behind the method and by an illustrating example the general application of the method is shown. The article then reflects on the use of the method. This is done by looking at the limitations of the Critical Path Method and comparing the method to other approaches of project scheduling. Furthermore, suggestions to improve the method are discussed.
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The idea behind the method
A project has several tasks that needs to be done in order of the project to progress. The tasks can have dependencies on each other and some of the tasks needs to be completed before others can start. The tasks can also be dependent in a way that they should be done at the same time. The dependencies of the tasks can be divided into three main cases.
- Technical dependencies - Beams cannot be placed without any supports and the construction of the beams therefore depends on the construction of supporting columns.
- Organisational dependencies - Walls can be painted before the installation of the roof is completed, but the risk of damaging the painting by dust and other things by this schedule planning is high. It therefore might be a good idea to reverse the order of the two tasks.
- Spatial dependencies - The installation of electricity and water pipes does not have any technical dependencies, but they often require the same space. In other words, they have spatial dependencies and therefore needs to be completed parallel to each other.
For even small projects the amount of complexities of these dependencies can easily be high. To handle the dependencies a technique known as the Critical Path Method has been developed. The method was developed separately during the late 1950’s by the U.S. Navy and DuPont. The basic idea behind the method is to identify all the dependencies and interactions between the tasks and point out the essential tasks that drive the project timeline. By doing so, the planning can be optimized to know which tasks that can be delayed and which ones that will affect the whole time of the project if not completed on time. The minimum length of time to complete the project is identified as the length of the sequence of tasks defining the critical path. Delaying any of the tasks on the critical path by either starting or finishing a task later then planed the whole project will be delayed. If any tasks outside the critical path is delayed it would not affect the project unless the delays are so extreme that these tasks become the new critical path. To reduce the time duration the project manager then knows which sequence of task that should be focused on because more resources on tasks which are not on the critical path will not affect the overall duration of the project. It is important to realise than even though many projects have only one critical path, multiple critical paths can occur.
Application and guidance of the method
In the following section the application of the method will be described. This is done in a general manner but with use of an illustrating example. The essence of the application is to fill out a sequence of critical path descriptors, as seen in Table 1. Based on the sequence of task descriptors, the critical path can be identified.
Step 1: Identifying the dependencies
To apply the method all the dependencies of the tasks needs to be identified. The network of dependencies can then be illustrated as seen in Figure 1. The duration estimates of the tasks will be explained later in this article, but for now the durations are shown with no comments. The durations are given in days, but the unit are in principle not important for the example.
