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An Introduction to Delay Analysis Methods

‘Project Delay’ is a term known to all the professionals in Engineering, Construction and Project Management (ECPM) industry, which is rightly so, as statistics and experience shows that up to 80% construction project fail to finish within the duration or completion dates specified in their construction contracts.

Delayed project means additional cost to project stakeholders. For owner and end user the additional cost may be due to late realization of project benefit, for project sponsor due to financial charge, and for contractor due to cost of the additional resources for the extended time, there may be several other costs and theirs combinations to the individual stakeholders – however, the fact that remains at core is – ‘Project Delay’ cost dearly. Adding to this, the fact that makes delay issues complicated is while the delay may be caused by a party, other stakeholders suffers as well.

So when it comes to business, where money matters, it becomes essential to find out, which all are responsible for the delay(s) and to what extent they are culpable. When more than one party is responsible for project delay, the other challenge is to find out what is contribution of the individual party in the overall project delay - this is also called apportionment of delays. Delay apportionment can be complex for long project and when the events those caused delays are many. And, here comes ‘Delay Analysis Techniques’ to help us solve this puzzle and avoid disputes. We shall briefly discuss Delay Analysis Techniques in this blog.

Critical Path Method (CPM) is the most commonly used tool for construction project planning, needless to say that the ‘Delay Analysis Techniques’ we are discussing here are based on CPM methods. There can be some additional ways to demonstrate the impact of delay on the project schedule such as, ‘S – Curves’ showing resources, earn value or cash flow can also be used to establish or substantiate delays, however, all these methods all are based upon on data/schedules prepared using the CPM.

Four most widely used delay analysis methods are - Impacted as Planned (IAP), Collapsed As Built (CAB), As-Planned v As-Built, Time Impact Analysis (TIA). I have extensively used TIA. In addition to be most rational and yet easy to implement, if supplemented with simple bar charts, TIA method can easily demonstrate and convince non-scheduling/non-claims professionals the causal relationship between each delay and its impact on the project schedule.

Although, there is no standardization of classification or taxonomy of Delay Analysis technique, the nomenclature I am using here is in the industry for quite some time and widely used.

a. Impacted as Planned (IAP)

In this method the original planned schedule for the project simply has the delay events superimposed or ‘impacted’ on to the Baseline schedule and the effect on the overall completion date measured by the change in completion date as a result of the delay impact. This method can be utilized both prospective and retrospectively.

This method possesses two major pitfalls. First it is assumed that sequence of the works remains the same as it was planned in the Baseline, which is not generally the scenario in the construction projects. Secondly, this analysis usually ignores all the delays caused by the contractor; therefore, answer generated is not necessarily based on all the actual delays that occurred on the project. In addition to this, certain type of delay event like lower rate of progress cannot be incorporated in this analysis.

It should be noted that the use of the Impacted As-Planned method for analysis may not be acceptable in certain jurisdictions, and therefore should be relied upon in very narrow conditions.

b. Collapsed As Built (CAB)

This method subtracts delays from the as-built programme and as a result determines the earliest date that the contractor could have completed the project if the delay event would not have occurred. This deductive approach to modelling delay relies upon the use of the as-built programme, therefore, generally limited to retrospective delay analysis. This method uses exactly the opposite philosophy to that relied on in the IAP and TIA (discussed later) methods. The ‘what if’ questions posed in the collapsed as-built method are ‘What if these delay events didn’t occur?’ or ‘When would the project have finished but for these events?’

The delay events are repeatedly extracted from the As-Built Programme in the reverse chronological order and it effect on movement of completion date is recorded.

This is a complex method and cannot be used prospectively.

c. As-Planned v As-Built

This method is based on the comparison between Baseline Schedule and how the actual work is carried out i.e. As Built Schedule, difference between the overall completions dates of the two being the basis of the delay claim. This technique can be used when sufficient as built information is available. This method can have several variant based upon its application on Baseline and As Built Schedule. At its simplest, comparison can be done between Baseline and final As Built Schedule.

On the other hand scenario analysis can be developed by making comparisons between Baseline and final As Built Schedule at different period of the Contract.

d. Time Impact Analysis (TIA)

An evolution of the impacted as-planned (IAP) method is known as the ‘Time Impact analysis’ (TIA). The TIA methodology differs from the IAP technique because it uses multiple baselines, rather than the original as-planned baseline, to measure the likely impact of delay events. Each Base Schedule is a CPM schedule representing the contractor’s intentions for completion of all remaining work, prior to the insertion of delay events. This can be carried out both prospectively or retrospectively. If done retrospectively scheduler places data date at the point in time when the delay event occurred.

The scheduler is required to create Base Schedule (not baseline schedule) contemporaneous to the for each delay event. This can be created as a new As built Programme based on the progress records or by identifying the contemporaneous updated Schedule closest to the date of each delay event and then updating each of those Schedule with update data up to the point immediately prior to the commencement date of each delay event.

These Baseline Schedules needs to include sufficient logic such that it is robust and reactive to change when rescheduled. If the Baseline Schedule does not contain sufficient logic to reflect the impact of delay, addition of further logic may be required. However, any such additions should not be added to simply make the schedule to react in a certain way in the favor of one party, and should be agreed/approved by another party. Also, such changes in Baseline Schedule can be reason of disputes when one party wins and the other loses the argument by making logical changes in the Baseline Schedule.

Delays are then inserted one at a time, chronologically, into their respective base Schedules and Project completion date is calculated for each successive delay event. Cumulative ahead or behind the Schedule scenarios are established including concurrency and party culpable for each delay.

Windows analysis is other Delay Analysis method which is derivative of TIA and CAB method. This technique adopts a given time window while doing delay analysis using TIA or CAB method.

While there can be many delay analysis method with their own merits and shortcomings, record keeping of day-to-day progress remains at the core of successful delay analysis.

While the knowledge of delay analysis technique is desirable for planning/ scheduling/ project control professional, and probably essential for claim analysts, there is something more important. Delays cost dearly to all the stakeholders: direct and consequential. Therefore, as a project management professional, it is recommended or even essential to put in reverent tool and technique in place so that the, delays if not fully prevented, are minimized. Project team needs a proactive approach to the event that causes delays rather than a retrospective approach using delay analysis techniques.


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