Whenever a change occurs or is proposed, the contractor must evaluate both the direct costs associated with implementing the change and the time impact of those changes, i.e. will the change affect how long it takes to complete the project. There are a number of methods available to calculate the effect of the change on the performance period. One of the most frequently used methods is the Time Impact Analysis (TIA). In this post, we will describe the method, outline the general procedure for performing a TIA, and discuss some of the strengths and weaknesses of the method from a construction delay claim perspective.
How the Time Impact Analysis Method Works
The Time Impact Analysis method was developed in the early 1980s and has become one of the most widely accepted methods for measuring the influence of an issue/change on the critical path of a project.
The TIA takes a new set of activities detailing the added or changed work and superimposes it in the CPM schedule. The completion date of the superimposed, or impacted, schedule is then compared with the unmodified CPM schedule. If the completion date changes, then the added work has an impact on the project performance period and a time extension may be warranted. If the completion date remains the same then the changed/delayed work has sufficient float and can be performed within the original timeframe and no time extension is warranted.
Here is a simple illustration. Consider a project that consists of only two activities. If a third is introduced in between the original two, the total project duration will be extended. This third activity represents the delay event or proposed additional work. By comparing the finish date of the two-activity schedule to the new three-activity schedule, the impact of introducing the new activity can be discretely measured. This is the fundamental principle of the Time Impact Analysis method.
The Time Impact Analysis Process
There are three general steps in performing a Time Impact Analysis:
- Develop a model of the impacted or changed work in the form of a fragmentary network, or fragnet. The fragnet is a subset of the schedule that consists of the activities and logic relationships representing the added/changed work.
- Identify which schedule update to impact. Generally, the appropriate schedule should be the last accepted schedule statused prior to the date of the impact. The most recent approved schedule is preferred because it represents the manner in which the project was being completed at the point in time when the change becomes known. This schedule update is often referred to as the “unimpacted schedule” in the analysis and serves as the reference point from which the delay will be measured.
- Create the impacted schedule. This is done by inserting the fragnet into a copy of the unimpacted schedule identified in the previous step. After inserting the fragnet, the CPM schedule is recalculated. The completion date of the impacted schedule is then compared with that of the unimpacted schedule to determine the effect of the change. The duration of the delay results from this comparison.
When to Use the Time Impact Analysis Method
The Time Impact Analysis method can be used in both forward-looking (prospective) and backward-looking (retrospective or forensic) delay analyses.
TIA is often the preferred method for prospective delay analysis. In fact, in 2015 the U.S. government revised its standard scheduling specification to require use of the Time Impact Analysis method for prospective (forward-looking) analyses. 
The Time Impact Analysis method is best applied in forward-looking (prospective) delay analyses as the viability of a TIA diminishes as more time passes between the identification of a delay/change and the preparation/approval of the TIA. When significant time passes, an owner may feel that unrelated contractor-caused delays have diluted the effects of delays caused by the owner. Eventually, the value of the findings of the prospective TIA is diminished to a point where a more thorough forensic analysis is more appropriate as the impact will have been absorbed into the project record/actual data. For these reasons, it is critical that prospective TIAs are prepared and reviewed immediately following the identification of a change or delay.
If you have questions about the Time Impact Analysis method of calculating the impact of a delay or change on your project – or other construction claim topics, contact Andrew Sargent or submit an inquiry.
- AACE International, Recommended Practice No. 52R-06, Time Impact Analysis – As Applied in Construction, Morgantown, WV; AACE International, May 2017.
-  Section 3.8.2 of UFGS-01 32 01.00 10 (February 2015)