How to indicate the critical path

How to indicate the critical path

One of the most recognised phrases within the construction and planning industries must be the phrase “Critical Path”. Other expressions that usually goes along with the Critical Path are delays, extensions of time and penalties. We have all crossed ways with a Critical Path of a project in one way or another, but do we know the importance thereof and do we know how to accurately indicate and reflect the true Critical Path on a construction programme?

Can a single programme have more than one Critical Path and can a programme’s Critical Path change throughout time? We answer “Yes” to both of these questions and it is important to know when these events do occur and when they are allowed to occur. Within this newsletter we will have a brief look at the definition of a Critical Path, provide a few pointers of how to create a true and accurate Critical Path on a programme network and illustrate by example how to filter critical activities within a construction programme.

A Critical Path is defined as the longest sequence of activities within a programme network that must be completed on time in order to reach the planned completion date. Critical activities are activities that forms part of the Critical Path. Should critical activities take longer than planned, the whole project will take longer than planned and it is therefore crucial to know which activities are indeed critical.

Critical activities can also be defined as activities with zero total float, meaning that the activities have no room for delay and should it be delayed, the completion day of the project will also be delayed. Total float is defined as the amount of float available for an activity to be delayed before it affects the project end date. Free float is defined as the amount of float available for an activity to be delayed before it affects the activity immediately succeeding this activity within the programme network. In practice, the Critical Path will change from time to time as activities are completed ahead of schedule or fall behind schedule. It is important to know what the exact and true Critical Path is at any stage of the project in order to focus attention and resources on critical activities.

How to indicate a Critical Path using CCS Software

The following image is used as an example to illustrate a Critical Path on a programme network. In most software packages, critical activities are indicated by colour red and non-critical activities by colour green. However, the colour schemes can be changed to suite the user’s needs. A few key factors are explained below;

In this example the Critical Path can be seen running from the start to the end of the programme network as the critical activities are indicated by red activity bars and the non-critical activities are indicated by green activity bars. It is important to indicate the Completion Date as a “Contractual End” date which specifies the end of a Critical Path or programme network. Activities with 0 total float is part of a Critical Path. Ensure that all activity links are dynamic and that there are no open-ended or unlinked programme activities. Should there be activities with open ends it means that these activities do not have a dynamic link to the project Completion Date and the software will assume they are part of a separate critical path, which creates a false impression as per the image below where a dynamic link was removed for illustrative purposes.

For one Completion Date there is usually one Critical Path, although there can be more than one Critical Path if different activity network paths have the exact same duration, however this is not common. There can be a number of Critical Paths in the same programme if there are separate Completion Dates for different construction areas or if there are Sectional Completion Dates specified. There will be a Critical Path to each Sectional Completion Date. Using CCS software one can filter critical activities within a programme by following these steps as indicated in the picture below;

  • Right click on the “Activity Description” column and hover over the “Filter” option with the mouse cursor.
  • Hover over “Logic filters” to show available options and choose “Critical Activities (no float)”
  • The programme is now filtered and only indicates the critical activities. This is a very handy tool for especially large projects

We would like to again highlight the importance of a Critical Path illustrated on a network programme. When done correctly one should be able to track which activities are critical throughout the progress of the project and plan accordingly. One would for instance plan and give priority to critical items in terms of resources and attention although non-critical activities should also not be neglected. Non-critical activities may become critical if they do not have sufficient progress and it is important to know when this change does occur in order to adjust accordingly. Should you have any additional questions regarding this topic please feel free to contact us.

 
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