Is there a theory of management that supports backward/reverse planning?

Question

I have found that project managers/project leaders use this common sense approach to planning. Namely, they already have a deadline, then they set milestones in a backwards order. They apply the same approach on each milestone to figure out what they need to do to accomplish the goal of each milestone.

Example:

Project: Super important business meeting in Las Vegas

I have an appointment in Las Vegas at 13hrs. So I set milestones in reverse:

• 13:00 - Arrive to Destination.
• 12:30 - Take a cab to my destination.
• 12:00 - Landing.
• 10:00 - Departure.
• 09:00 - Check-int at the airport
• 08:30 - Leave home

After identifying the milestones by going in reverse I can tell that I need to leave home at 8:30 if I want to have enough time to arrive to my destination on time.

I have seen this approach being used in planning sessions for big and complex projects and I would like to know if this approach is backed up by any sort of theory of management. Our team is trying to learn how to do Scrum and so far I have not found this sort of approach in the materials that I have read.

Answer 1

Mikado Method

On a technical basis, this sort of "reverse planning" can be done using the Mikado Method. The best in-depth treatment of this method can be found in The Mikado Method, Ellnestam and Brolund, 2014. While not optimized for project management, parts of the method (e.g. visualizing the dependency tree) may be useful in scoping a project, developing a work breakdown structure, or identifying milestones.

Critical Path Method

On a project management basis, there are a number of techniques for scheduling backwards from a set of defined milestones based on dependencies. One such technique is the critical path method, using a modified PERT chart or activity-on-node diagram to graph out the project's schedule. You can certainly use this method by starting with a target end date for the project, and then working backwards along the critical path to determine the appropriate start date.

Answer 2

CodeGnome provided an outstanding answer. To add to it slightly: I have observed in my experience that backwards planning is done nearly exclusively. Deadlines are typically driven by some business or legal need; thus, the project has no alternative but to work backwards from there. The problem with this method is that the resulting plan may have no basis in reality at all or present with a high likelihood of failure. But as the planning iterations develop, it is our nature (Optimism Bias) to begin accepting the plan as doable and even guaranteed.

So while you may find backward planning common sense and that you may be forced to backward plan because of a deadline, you should still understand the risk of that project by planning normally, forward planning, to see the size of the gap / risk you have.