Project S Curves - Are they really useful?
S - Curves are very popular in construction industry particularly in EPC Projects. It is a tool which helps to provide quantitative progress.
But how effective they really are for providing insights and actual performance of your project.
Let me take an example of Project A. The project plan at the start is given in Table 1.
Activities 1 to 4 are the ones on the critical path (which drive the project duration of 7 months). Monthly planned progress percentage is indicated at the end of the table. The progress is measured using S-curves and project is reviewed at the end of each month.
The contractor is mobilised and starts the work in January.
Refer Table 2. The Project team has been reviewing the progress performance at the end of every month. The progress is satisfactory for the months of January and February as the progress is on par, actual percentage is equal to planned percentage. Everybody is happy.
But see what happens when the project is reviewed at the end of March (Table 3), it is observed that against plan of 32.3 % the archived progress is 29.2% a variance of 3%. The contractor is instructed to expedite the work and catch up the delays. The contractors acknowledges the slight delays and readily assures to catch up.
If you observe the table 3 carefully, you will notice that the problems started in the month of January itself which revealed only later.
The contractor has smartly delivered 200 Cu.m in January but he has achieved this by taking up non critical work of roads, boundary wall and security office etc instead of executing the main foundation earthwork work which is on critical path.
Same is repeated in February as well where he achieved the planned target of 325 Cum.
At the end of march, although there is a slippage of only 3% in overall progress, but have a look at the slippages in critical path activities.
Earthwork for foundation - Planned 60% vs Actual 35% Variance - 25%
RCC concrete - Planned 25% vs achieved 3%, Variance - 22%
So your project is not behind by 3% but much more. S-curves do not indicate by how much.
Now, let's again review the progress at the end of June (Table 4).
The contractor has indeed tried to catch up by doing more work in the critical activities, however there may be upper limitation due to various factors such as equipment mobilisation, resources, presence of other contractors, productivity issues etc.
Refer the Project S curve.
The forecast shows that the project will be delayed by a month as the structural erection will spill over to the month of august.
Conclusion
Civil Engineer
2yS-Curve is prepared for entire scope of project from the project activities ( It doesn't matter wheather it is cost or wieghted units). Cost is most suitable since no one can debate since it will be taken from BOQ. If it is done considering all the activities including design and procurement, it will give you correct indication when you update regularly with out missing any
Project Management Specialist
2yS-Curve is not followed for identifying delayed activities in Status reports. Any Project management software gives the Critical activities in a Detailed Gantt chart view with driving predecessors and Successor activities. Once these tasks are identified, Project manager can strategize depending on the resources and authority at his disposal to bring back the schedule to Base line plan. S-Curves are normally used as dash board presentations. However I appreciate the the article has generated curiosity the importance of S-Curve in Project monitoring.
Senior General Manager | Infrastructure
2yGood analysis. As you know S Curves are generated based on weighted factors. So to have a correct picture more weightage needs to be given on the legacy critical activities. For example in a power plant network the a activities relating to turbine and boiler always fall on the critical path . By the way Project managers do not rely on the S Curve alone but go by the project network which gives the list of critical path activities and how they are performing.
Project Management Professional PMP® / Capital Project and Turnaround Management Specialist / Refining and Petrochemical Industries / Instrumentation and Controls Specialist.
2yNaveen Lopes excellent article and truly right. We can earn value but if not for activities in critical path there will be a moment in which delay will be shown. It will give us just a false illusion of progress. As you indicate, critical path must be monitored separately and with special focus to avoid extension of project in time.