Keeping the Project on Schedule

The management of any project requires a multitude of abilities, duties, and responsibilities of the Project Manager (PM). Some of these responsibilities consist of, to name a few, contract administration; analyzing and issuing change orders; inspection; and coordination between the multiple teams. Project administration includes the oversight of the project through the eyes of a cost and manpower loaded schedule which is of particular importance and the focus of this report.

Manpower and cost are two of the key elements of the schedule, both of which must be regularly monitored to give the PM and project sponsor early warning signs on how the project is progressing and raise a red flag when the project is starting to "head south." By monitoring these two elements in the project schedule as well as the accuracy of the schedule's construction logic, the PM maximizes the opportunity to keep the project on schedule.

Even in a closely monitored project, however, there are many reasons for a project falling behind schedule. The following are major causes of project schedule slippage:

  • Changed work
  • Faulty logic
  • Insufficient manpower
  • Team's failure to work on critical path activities
  • Unrealistic activity duration

Delays due to changed work

Assuming that the implementation teams are reasonably following the approved schedule and working on the critical path activities, the project may fall behind schedule from month-to-month. One reason for the slippage may be change order work affecting the critical path; this slippage would show up on the monthly analysis of the parallel runs implementing the change orders into the logic and analyzing the schedule to determine potential reasons for slippages. If change orders are causing the project slippage, a time extension is warranted and should be issued adjusting the project completion date to reflect the affect of the change on the work's schedule.

Faulty Schedule Logic

After each monthly update it is imperative to re-evaluate the schedule logic and adjust the logic if necessary as part of the update process. All too often the update is performed mechanically with no consideration given to re-evaluating the plan for the balance of the project. To update a Critical Path Method (CPM) schedule whose foundation (logic and/or estimated durations) is outdated will typically result in a misleading forecast and erroneous reports.

Insufficient manpower

Based upon manpower data initially obtained from the teams' leads in the Day-1 CPM, the project scheduling software can give the PM the ability to generate reports identifying manpower requirements for individual trades. These reports could include a two-month projection (window) of manpower requirement by trade/work area or a projection of manpower by trade for the upcoming month.

Project slippage can often be attributed to a lack of manpower or insufficient manpower on critical path activities. The easiest way to verify the adequacy of the projected manpower is to compare the actual manpower indicated on the daily logs with the manpower report generated from the previously updated schedule. If the project is continuously slipping from month-to-month, the cause may be a lack of manpower.

A "cost-loaded" CPM provides a method to determine a cash flow forecast for the project on a month-by-month base. Comparing the actual project percent complete to the planned percent complete for the same period will give the PM an indication as to how the project is progressing. If the actual cash flow is lagging behind the planned or projected cash flow, chances are the project is heading for potential problems if it is not having problems already. Usually, unless there is unrealistic cash flow data in the schedule, the actual percent complete compared to the as-planned cash flow is a good barometer of how the project is progressing and whether the project is on schedule.

Team's failure to work on critical path activities

What is critical today may not be critical tomorrow. The critical path identified in the original or Day-1 schedule, will only remain the critical path if everything goes according to plan. Experienced PM knows that this is almost never the case. Although CPM is a well accepted and powerful tool for managing the day-to-day events on a project, the accuracy of the calculated milestones or project completion date is directly dependent on the completion of every critical task taking no longer than originally estimate. If the team fails to work on the critical path or works on it part time, the project schedule will slip a day for a day that the team did not work on the critical path. The project slippage will be reflected in the next month's update. A report that can assist the PM is the hot list report, which reflects the activities the contractor must be working on during the reporting period to maintain the projected project completion date. It is a good practice to review the hot list report at the weekly progress meetings and discuss the status of the work effort on the critical path and near critical activities. The PM must monitor the near critical activities as closely as the critical activities to prevent them from becoming the next month's critical path. A near critical activity is defined as an activity whose early start and late start dates fall between the current as-of date and the next scheduled update date. Doing so will keep both the PM and the team focused on the status of the project and the progress on the critical path.

Unrealistic activity duration

For any given activity in a schedule, a delay may occur i.e., late delivery of material or equipment, which is truly unforeseeable, and the Day-1 duration for the activity may have been entirely appropriate. This is not always the case; all too often the duration of activities in a CPM network are guesses that may be unrealistically short, calculated by how much time the team has to complete the project rather than how long the activity will actually take to complete. Another explanation is that the planned duration is based on an unrealistic team size which will never be achieved. Conversely, duration can be longer than necessary based on a planned smaller team size where in actuality the team size is much larger than originally planned. Comparing a similar area of work and evaluating its duration, and adjusting the duration for the next portion of work according to the historical as-built information, can easily correct this situation and give the PM a more realistic schedule.


Updating the schedule monthly is not sufficient to keep the project on schedule and prevent the project completion date from slipping. The updating process must include a systematic review of the schedule's logic, duration, manpower, cash flow and change orders, as well as an analysis of the actual progress of the work to date.

The above represents an explanation of the various major causes of schedule slippage. Remember, the CPM schedule is only as good as the information which is used in its preparation and maintenance, and the ability of the PM to identify the necessary activities, determine their interrelationships, accurately estimate the time necessary to complete these activities, and translate the information generated by the up dating process into realistic solutions to problems arising on the project.