You will rarely find a project which does not encounter some sort of delay. Some very common causes for delays are design changes, specification changes, unexpected execution problems and obstructions.
A delay could be critical or non-critical. A critical delay would cause delay to the critical path which in turn would delay the project as a whole. A non-critical delay on the other hand delays only a portion of the work without impacting the project completion.
Classification of delays is not being covered here and only deifferent delay analysis techniques will be discussed here.
Project schedules are extremely important in evaluating extension of time claims because they help in establishing entitlement to time as well as cost. The following are some common delay analysis techniques:
- Impacted As-Planned Schedule Analysis
- Collapsed As-Built Schedule Analysis
- Window Analysis Method
- Time Impact Analysis
There are various important factors which must be considered while choosing an appropriate schedule delay analysis methodology. Just like every single project, each claim is unique and has different contract requirements, situations, complexities, and legalities, among other factors. The selection of a particular delay analysis method should be based on professional judgment and diligent factual research and evaluation.
- Impacted As-Planned Schedule Analysis In this method, the delays are inserted as individual activities and incorporated in the baseline schedule to assess the impact on the project completion date. This is then compared with the original planned completion date or the actual completion date.While this technique may still be used in some cases, it is not widely practised presently. Not accounting for the as-built (or actual) history and the ever changing critical path over the course of the project are the major disadvantages of using this technique.
- Collapsed As-Built Schedule Analysis The collapsed as-built delay analysis methodology begins with the as-built schedule and then accounts for delays or changes, removing them to demonstrate the effect on the completion date of the project if there was no delay or change. Generally, this technique is used where reliable as-built records exist, but baseline schedule and/or regular schedule updates either do not exist or are unreliable. As is obvious, this is essentially a retrospective technique where the scenario is recreated going backwards.After identifying project delays and then removing them from the developed time record, the resulting collapsed schedule will show when the project should have completed instead of completing when it did with the delays.
- Window Analysis Method The window analysis method is a critical path analysis technique. It involves a comparison of planned and actual critical path performance during any period of time. This time period is referred to as a window of time or simply as a window.First, the total project duration is divided into a number time periods (windows). The schedule within each window is updated to reflect the actual durations and sequence at the time of the delay while the remaining as-planned schedule beyond the window period is maintained. Analyses are performed to determine the critical path changes and new completion date. This new completion date is compared with the as-planned completion date prior to this analysis to give the amount of delay during the particular window.The advantage of this method is that the changing critical path is taken into account and the more windows are used the better is the accuracy of the result. However, it is a time consuming process and needs realiable project records in addition to loads of effort and research.
- Time Impact Analysis Time Impact Analysis (TIA) is a simplified analysis procedure. This is a variation of the window analysis method. It deals with simulating the effects of a specific, single delaying event. This makes it a projection tool or a forward looking tool, i.e. creating the probable scenario expected after lightning strikes.The difference of TIA with window analysis is that TIA focuses on specific delays. Time periods as such are not analysed in this case. Rather, the schedule is prepared closest to the delay event and is then impacted to determine the new completion date. The comparison between the new completion date and the completion date just before the delay event gives the impact of the event.