Project Management Institute

Rolling wave approach to project management



Joan Knutson

How often have you been asked for estimates of the duration and the cost of a project and have given answers before you really fully understood the scope of the effort? How often have you been correct? Although you were assured that these estimates were only to be ballpark figures, how often were they set in concrete, never to change?

This month's column discusses how this scenario develops, why this approach seldom works, and what can be done to structure a more realistic alternative. To address this issue, consider an analogy:

Imagine that you are an expert mountain climber, standing at the bottom of an imposing mountain you've never see before. It's your job to climb over this mountain and reach the bottom on the other side. The person who is funding your expedition asks you “How long will it take you to climb over and get to the bottom on the other side of the mountain, and what resources will you need?”

You think: “How do I know how long it is going to take to get to the bottom on the other side or how much it will cost to get there? I've never seen this particular mountain before.”

Would “I don't know” be a satisfactory answer to your sponsor? Probably not. The sponsor hired you because of your expertise in mountain climbing and expects you to come forth with some reasonable answers. On the other hand, if you shoot from the hip, you know the accuracy of your guess will be weak at best, and sooner or later you will have to confront your error. You seem to be caught in a lose-lose position. Is there no alternative?

Consider the Rolling Wave, or Phased, approach. This method can both satisfy your sponsor and add a sense of integrity and credibility to your commitments. The Rolling Wave approach to project management suggests that the project planning effort “rolls out” detailed plans for the foreseeable future and, as the project evolves, periodically reevaluates the completion dates and costs.

Let's reexamine the mountain climber analogy. At the beginning of the climb, you stand at the bottom of the mountain, with minimal knowledge of what confronts you. But your mountain climbing background and experience, combined with historic data gathered from other people who have tried to climb this mountain, allows you to approximate the time and resources required. Note the term is approximate, not estimate. When approximating, afford yourself all the flexibility possible. For example, it will take six to nine weeks to climb the mountain and reach the bottom on the other side, will require ten to twelve people, and will cost $50,000 plus 10 percent.

Provide the sponsor with a detailed plan, and present everything required to prepare the party to start moving up the mountain. Determine the necessary equipment. Pinpoint the right people. Acquire and study all the information about this particular mountain. Plot a route of travel. This is called scheduling through the first Planning Horizon. A Planning Horizon—planning out as far as you can see—is a target that may be stated as the number of days, the next phase of the project, or until the next milestone or deliverable is reached.

Thus far you have provided your sponsor with an approximation of the requirements in time and resources to finish the total effort, and a detailed schedule for the first Planning Horizon.

Now the benefits of Rolling Wave come into effect. You track to the detailed plan that was established for the first Planning Horizon. At the end of each phase, many unknowns have been resolved and many decisions have been made. In our mountain climbing analogy, after selecting the equipment and people required to make the climb and mapping out the route, then the planning for the next phase begins.

This step—acquiring the resources and preparing to start the climb, becomes relatively easy. Furthermore, the approximation of time and resources at this stage can be refined with a higher level of accuracy and greater confidence. At each subsequent reevaluation, the projections of the final deadline and costs become more realistic. There will come a point when enough information is available and the scope is well-defined, making further reevaluations unnecessary.

Selling the Wave

Although this approach may be logical to those in project management, how do we sell it to our management clients? Start from the premise that the old way has not worked well. It's not realistic to formulate a series of time, labor, and budget commitments on Day 1, and then “set them in concrete.” Regardless of whether estimates have been requested or mandated baselines have been announced, the Rolling Wave approach provides you with a practical methodology to evaluate and reevaluate the validity of commitments and a means to support refinement of those commitments, if and when appropriate.

Perhaps this argument would be more convincing if you had better estimating tools. Therefore, the July column will discuss strong project management estimating techniques.

Joan Knutson is president and founder of Project Mentors, a San Francisco-based project management consulting and training firm.

This material has been reproduced with the permission of the copyright owner. Unauthorized reproduction of this material is strictly prohibited. For permission to reproduce this material, please contact PMI.

PM Network • June 1996



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