Four ways project schedules are limited and what to do about it
The speed with which a project schedule can be completed is limited by four factors:
- The logical order in which activities need to be completed
- How long each individual activity will take
- How many key resources are available at key points in the project
- Imposed dates.
This guided discussion session will start with a very brief introduction on creating schedules with an eye toward each of these limitations. Next, several proposals will be made regarding how to deal with each limitation. The attendees will be asked to offer additional suggestions via Post-it® Notes. Finally, each attendee will be asked to prioritize how useful he or she believes each suggestion will be in his or her own work environment.
One of the most frequent questions a project manager is asked is some variation of “How long will the project take?” This is almost like kids on a car trip asking their Dad, “When will we get there?” Just as several factors will influence when the car trip is complete (distance, road conditions, traffic, rest stops), several factors influence how long a project will take. Students of project management first learn that the logical order in which they can work on project activities and the expected duration of each constitute the project schedule. In practice, they very quickly learn that being able to calculate a critical path based upon the order and duration is not enough. There are several ways in which a creative project manager may at least partially overcome both order and duration to speed up the schedule. However, two other factors—namely, key resource availability and imposed dates—can also limit a project schedule. Creative project managers strive to understand and mitigate the impact of each of these limitations. The combination of methods used to overcome schedule limitations will vary from project to project because of the specific circumstances each faces. Therefore, project managers learn both various methods for overcoming schedule limitations and which are likely to be useful on their project.
How Project Schedules are Limited
The first limitation to project schedules is the logical order of activities. For example, a hole must be dug before cement can be poured into it. A project manager needs to have identified each work activity and then for each, asked the question, “What needs to be done before I can start this (in other words, what are the predecessors)?” This is enough information to construct a network depicting the project schedule. Project teams sometimes do this with Post-it® Notes so they can all visualize the order in which the work will be performed. It is important to identify all activities, since any missing activity will cause the schedule to be longer than planned.
The second limitation to project schedules is the expected duration of each activity. Duration is “the total number of work periods (not including holidays or other work time) required to complete a schedule activity” (Project Management Institute, 2004, p. 359). Activity duration and logical order are combined to form network-based project schedules. They are what schedule calculations performed by either software or by hand require at a minimum. Introductory students are given problems with activity lists, predecessors, and expected durations and told to calculate the schedule. This is an important starting point, but not enough for many projects.
Key Resource Availability
Many organizations run lean in efforts to keep costs low. That means, there are often few choices as to who will perform the project activities. If those key people (or other resources, such as machines or facilities) are already scheduled for something else when they are needed for the current project, it can cause delays. Often the project manager will not know exactly when each key resource is needed until the first cut of the schedule is developed, based upon the logical order and the expected activity durations.
Customers, sponsors, and other key stakeholders sometimes impose dates that limit project schedules. These imposed dates can specify that a given activity may not start until a particular date, must be complete no later than a particular date, or progress must be reported on an exact date. Each of these constraints (no earlier than, no later than, and exact dates) can limit the flexibility and speed of a project.
Basic Methods to Overcome Each Limitation
The logical order of work activities used to create a project schedule is the best guess of the project manager and team of the sequence in which the project work ideally should be performed. In practice, many times the order originally developed proves to require too much time to complete the project. Therefore, a variety of approaches can be used to relax the order enough to complete the project more rapidly. A project manager may employ more than one of these approaches—they can be used together. Some of the methods commonly used to reduce the impact of an overly restricted logical order include the following:
- Reverse phase scheduling, whereby the people who will actually perform the project work start logically at the end of the project and work backward by continually asking, “What do I need before I begin work on this deliverable?” This can sometimes eliminate a few predecessor relationships that are not really needed.
- Mandatory and optional dependencies, whereby the project manager and/or team ask, “Which of the dependencies we have listed are truly mandatory and which are just desirable?” This can allow a project team to eliminate a few predecessor relationships that might be nice but are not really needed.
- Alternative dependencies, whereby the most common dependency (finish the preceding activity before the successor activity can start) is replaced by other logic. The most common of the alternative dependencies are finish-to-finish, when the first activity must be complete before the other is complete, and start-to-start, when the first activity must start before the other one may also start. Alternative dependencies allow for more realistic depiction of real-world limitations.
- Leads, whereby a successor activity is scheduled to begin before a predecessor is complete, and lags, where a predecessor activity does not start right away after the predecessor. These also allow a project schedule to be constructed with more real-world considerations. Leads and lags are often combined with alternative dependencies.
The activity durations are the best guesses of the project estimators. They may be very good estimates or wild guesses. Enabling estimators by providing them training, feedback, examples, and templates can help the overall quality of the estimates. A few additional methods include:
- Overall optimism or pessimism—try to create realistic expectations
- Omissions—use checklists, templates, lessons, and so forth
- General uncertainty—use rolling wave, learning curve, and aggressive schedule management
- Special cause variation—use risk management
- Common cause variation—use PERT, Monte Carlo, project buffers
- Merging—use milestones, feeding buffers, and float
- Queuing—use staggered starts, resource leveling, resource buffers
- Multi-tasking—use project prioritizing and careful authorizing of non-critical activities
- Student syndrome—use float and critical path meetings
- Not reporting early completion or rework—use project culture cultivation, project communications, and contract incentives
(Leach, 2003, p. 44; Kloppenborg, in press, chap. 7).
Key Resource Availability
The schedule based upon logical order and activity duration estimates is only realistic if the people and other key resources that will be needed to perform each activity are available exactly when they are called for in the tentative schedule. Therefore, at this point, several strategies are called for to ensure the resources are available. Resource availability strategies include the following:
- Determining the project's specific resource needs. These can include knowledge and skill on the part of workers, support needs (such as information systems), co-location issues, and many other practical concerns.
- Identifying potential resources both within and external to your organization. Considerations for each potential worker identified may include work functions, professional discipline, skill level, physical location, costs, and contractual issues (Rad & Anantatmula, 2005, pp. 68–72).
- Determining availability of desired resources. Many project managers will start the process of ensuring key resource availability long before they know exactly what resources they will need and exactly when they will need them, since the sooner key resources are identified, the more likely it is they will be available when needed.
- Considering timing issues when adding key resources. If they are added too soon, it costs more money. If they are added too late, they may not be available. Assigning them early often helps with planning and buy-in.
- Assigning key resources to each activity and determine how much work each is assigned at each point in time. Software is particularly useful here, as the resource assignments can be shown on a Gantt chart, then the time demands for each can be summarized on a per-day or per-week basis to show when each is overloaded.
- Dealing with identified resource overloads by methods (Kloppenborg, in press, chap. 8) such as:
- Assigning overloaded activities to other workers
- Splitting overloaded activity into two parts
- Reordering the activities
- Securing additional resources
- Reducing project scope
- Informing the sponsor
- Postponing non-critical tasks to level the resource load
- Delaying the project schedule
- Using critical-chain approaches of avoiding multitasking and using buffers.
Overcoming schedule problems caused by imposed dates requires more behavioral approaches. The information developed by overcoming each of the other three limitations can be very useful. Ultimately, however, dates are frequently imposed by clients, sponsors, and other important stakeholders. Some imposed dates are truly important to the stakeholder imposing them and are rather inflexible. Those may require significant support before they are changed. Others, however, may have been established out of convenience and might be easier to change. Generally, the sooner a change is requested, the more specific information you provide to substantiate your rationale for needing the change, and the more powerful stakeholders you have on your side, the more likely you are to get relief from an imposed date.
Additional Methods to Overcome Each Limitation
Now it is time for audience participation. The first part of the participation is to brainstorm additional methods for overcoming each limitation. Participants will each be assigned to one of four groups. Each group will brainstorm additional means to overcome each limitation and then decide which three of those additional means they believe are most useful to projects in general (not limited to any one industry or type of project).
Key Resource Availability
Prioritize Methods for Your Projects
Now, considering both the basic methods of overcoming limits to project schedules and the additional methods developed in this workshop, determine which methods you believe might be most useful for your projects. Also, state why you feel each method might be useful.
|Methods for Overcoming Logical Order||Why Useful?|
|Methods for Overcoming Activity Duration||Why Useful?|
|Methods for Overcoming Key Resource Availability||Why Useful?|
|Methods for Overcoming Imposed Dates||Why Useful?|
Many constituents are eager to know how long a project will take. There are four essential limitations to project schedules: the logical order in which the activities can be performed, the duration required to perform each activity, the availability of key resources exactly when each is needed, and any dates imposed by stakeholders. Precise information, often developed through use of project scheduling software and extensive communications, enables a project manager to better understand exactly how each limitation impacts the project. A variety of methods can be used to overcome the limitations. The key is to determine which methods are best for a given project.
Project Management Institute. (2004). A guide to the project management body of knowledge (PMBOK® Guide) – Third Edition. Newtown Square, PA: Project Management Institute.
Kloppenborg, T. J. (In press, available February 2008). Contemporary project management. Mason, OH: Thomson Southwestern.
Leach, L. (2003, June). Schedule and cost buffer sizing: How to account for the bias between project performance and your model. Project Management Journal, 34(2), 34–47.
Rad, P., & Anantatmula, V. (2005). Project planning techniques. Vienna, VA: Management Concepts.
© 2007, Timothy J. Kloppenborg, Ph.D., PMP
Originally published as a part of 2007 PMI Global Congress Proceedings – Atlanta, GA, USA
Earning a scheduling certification helped three project professionals deliver more precise estimates — and become better leaders.