Time Impact Analysis: Extra Work and the Effect on the Finish Date

Project Managers are often eager to undertake additional challenges.  Experience shows the seasoned manager under-commits and over-delivers as opposed to the alternative (over-committing and under-delivering).  There are real world processes and tools in place that can help the Project Manager understand and make realistic commitments.  Before commitments to accept extra work are communicated, there exists a recommended practice to understand and analyze the impact of a change to the work.  AACE International, the Authority for Total Cost Management® has published recommended practice number 52R-06 which spells out the practice for taking on more work, a change, and reasonably communicating the impact.  This analysis is performed rather easily using Microsoft Project.

Time Impact Analysis (TIA) is a scheduling technique used to assess and quantify the effects of an unplanned event, namely a change which increases the work scope, but can be used in other ways.  A TIA can also be used to evaluate potential impacts to the schedule for acceleration or delay.  A TIA is forward-looking.  Requirements for performing a TIA stipulate that your schedule must have a valid critical path.  The TIA is applied to the most recently updated and accepted critical path method (CPM) schedule.  The TIA permits the team to examine and analyze the change of project completion between the original plan, the non-impacted schedule, and the impacted schedule with acceptance of additional work.

According to AACE International’s recommended practice No. 52R-06, there are eight steps for understanding scope change and the impact to a finish date.  Those eight steps are:


1)    Develop and approve schedule fragnet to model the extra work.  Provide a CPM schedule of the additional changed work and get the schedule approved.

Although the TIA method can be used in any project, including information technology, facility construction, business acquisitions, maintenance, and production plant outages, this example is an engineering project related to the electrical transmission grid.  The change from an existing originally planned Oil Cooled Breaker to a Gas Cooled Breaker in a substation is examined and the fragnet of the extra work is documented.

NOTE: The screenshots below are with Project 2013, but TIA can apply to all versions of Microsoft Project.


2)    Obtain the most recently updated approved schedule.  This supports and gives reason to routine updating of the schedule.  An older schedule update should not be used, rather, use the approved schedule that most recently reflects where work status stands.


3)    Set the durations of the extra work activities (fragnet) to zero.  Merge the MS Project 2013 files of the current schedule and the fragnet to get the schedule below.



4)    Insert the approved durations into your fragnet (schedule of new work) and recalculate the critical path.



5)    Identify the activities used to measure the delay.  Here is a special note: if your inserted fragnet does not show up on the critical path, it will not delay the project.  However, there may still be a resource availability issue.  Resource capacity and existing workload can also be checked, but that is a topic for another paper.  In the case above, redesigning the work based on the change in specifications of a breaker causes a time impact to the remaining tasks.


6)    Determine the correct time impact of delay.  In the above example, the project is already delayed due to slow progress on task 7, and overall the project is beyond the baseline by 10 days.  Changing the work further delays the critical path and the time impact analysis illustrates an additional 12 day delay to the projected finish date.  Overall, the impact from additional work to the project finish is 12 days.


7)    Determine the actual dates of the delay.  This step is calculated and shown above.  The yellow double arrow shows the delay due to the extra work.


8)    Lastly, eliminate any delay that was already in the schedule (the difference between the finish date with the fragnet and the recently updated CPM schedule is the delay impact due to acceptance of the change / extra work).


That concludes using Microsoft Project to implement recommended practice 52R-06 as defined by AACE International.  This analysis can be used in all types of projects.  This schedule analysis and impact method does not determine cost impact to one’s schedule.  Performing a TIA helps PMs understand the impact of extra work, and gives PMs the tools to communicate impact to the project finish date.  The sooner the customer knows the impact of change, the more effective one is at managing and controlling the change.

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Tony Woodrich is President of the Southeastern Michigan MPUG.  Tony spends his time supporting clients implementing project management.  Prior to joining the commercial sector, Tony served his country as Captain in the United State Air Force, buying, building and maintaining various defense R&D projects, systems, and facilities. Tony is a PMP, a CCP, has a MBA from Bentley University in Massachusetts, and a Civil Engineering Degree from the United States Air Force Academy.  Tony has also volunteered on the board at the Camp Newton Club, an outdoor non-profit nature conservancy and for a Florida Beach co-operative.
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  1. good.

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