This recommended practice (RP) for prospective time impact analysis (TIA) is intended to provide a guideline, not to establish a standard. This recommended practice of AACE International on TIA, as applied in construction industry projects and programs, provides guidelines for the project team to assess and quantify the effects of an unplanned event or events on current project completion. While TIAs are usually performed by a project scheduler and can be applied on a variety of project types, the practice is generally used as part of the total cost management (TCM) change management and forecasting processes.

This recommended practice focuses on the basic elements necessary to perform a time impact analysis (TIA) to a construction project CPM schedule. Necessary considerations and optional analysis practices are described. The TIA is a forward-looking, prospective schedule analysis technique that adds a modeled event or events to an unimpacted schedule to determine the potential impact of that event(s) to the longest path and therefore project completion. The prospective TIA procedure is performed while a project is on-going, and thus has a forward-looking or a prospective analysis perspective in near-real time context. Retrospective (forensic) TIA is not typically required during the execution of a project as a prospective TIA is a forecast designed to facilitate a timely contract adjustment prior to the actual work being completely performed. Retrospective TIA analysis is addressed in AACE International Recommended Practice 29R-03, Forensic Schedule Analysis.

This TIA practice concerns itself with time aspects, not cost aspects of projects. The time impact must be quantified prior to determining any potential cost implications. No practical advantage is obtained by including cost factors into a time impact analysis. Linking time and cost into one analysis implies that time impacts are a function of costs, which for the purposes of a prospective TIA is not necessarily true. Separating time analysis from cost analysis makes TIA inherently easier to accomplish and accept contractually, thereby eliminating the cost-driven considerations.

A TIA may also be performed in-house to evaluate the potential or most likely results of alternatives being considered by the contractor in terms of means and methods of completing the project. This is commonly referred to as a what-if analysis.