Let’s assume you have your project mapped out! You have your list of deliverables and you know the activities required to produce those deliverables. Is there something missing? Like a hiking trail with markers telling you definitively where you are on the trail wouldn’t it be helpful to have markers in your project schedule telling you exactly where you are in your schedule? Thus enters the value of milestones.
Milestones are like major trail markers you can insert in your schedule. They help you locate exactly where you are in your project. A Work Breakdown Structure (WBS) is useful because it organizes the project deliverables in a hierarchy with systems at one level and then components at lower levels. Once your work breakdown structure is in place then you are ready to consider the activities required to produce those deliverables. Your schedule then becomes a list of WBS elements or deliverables and the associated activities or tasks required to make those deliverables.
In scheduling software, such as Microsoft Project, the WBS elements or deliverables are known as summary tasks. And the associated deliverable producing tasks are listed below each summary task and indented to show their relationship.
Once you complete all the activities associated with your deliverable you know you have completed a portion of your project. Keep track of the completion of all your deliverables and you know roughly how far along you are in your project. But wouldn’t it be nice to have larger markers in your schedule.
Markers to tell you are at the trailhead, the beginning of a project, or you are entering the design phase of the project. Or, perhaps, your project has reached a substantial completion marker where you can begin to consider quality assurance, product delivery, and, possibly, project closeout. These can all be done with the convention known as milestones.
Milestones are unique activities in the schedule because they have no duration; they consume no time. They also do not consume resources, so they have no resource assignments. They do, however, have relationship assignments like most other activities. So they are well connected to the activities in a schedule. And the schedule leads through the milestones the way a hiking trail goes through the trail markers. They also have a status, where they are either not started or completed.
Their definitive not-started/completed states are because they, again, have no duration. They are, however, more than just switches in a circuit. They are guideposts telling you where you are or have been. Primavera P6 milestones, in particular, describe whether you are at the start of a phase with its start-milestone or completion of a phase with its finish-milestone.
With this knowledge of knowing where you are and/or are going you can dive down deeper into the nuances of your schedule map and look at the activities that are producing the deliverables.
Primavera P6 Milestone Example
Let’s take a look at a sample schedule with the most basic milestones. Here we have displayed in Figure 1 a complete Primavera P6 schedule.
The milestones on the Gantt chart are represented by black diamonds. Notice first in this schedule that the milestones are grouped together with all the high level activities. Milestones may be spread throughout the schedule or grouped together. It is helpful, particularly for large projects to group the milestones together. And you can follow the relationship lines to the activities the milestones are pointing to. In our demonstration schedule we have two milestones that occur at the same time and together signify permission to commence the project and the project start.
Project start is connected to both the project management activity, which is a level of effort activity, and the first occurring activity ‘Drain Piping System’ that is one of two activities producing the ‘Demolition Piping’ WBS element, i.e. deliverable. If you follow the schedule relationships you will eventually come to the last activity required to produce the ‘Quality Assurance’ WBS element. This is connected to the ‘Close Project’ finish-milestone activity in a Finish-to-Finish relationship. Last of all ‘Close Project’ is connected to the Project Management activity in a Finish-to-Finish relationship.
The milestones in this schedule help to highlight the beginning stages of the project and the closing stages. In larger projects milestones would help to mark the different phases of the project schedule.
In larger more complex schedules, it is common practice to place all the major milestones at the top of the schedule. They are then linked using relationships to their driving activities further down in the details of the critical path. This provides an easy view of where you are in the project without having to drill down in to the details of the schedule to find you key milestones.
A milestone activity with no duration and no resource assignments, nevertheless, serves a pivotal role as the schedule guidepost markers. Milestones may signify the start of the project or phase like design phase, structural phase, quality assurance phase, or closeout phase. They tell you where you’ve been or where you are going. They point to the activities that produce the deliverables.
Grouped together they can help you find your place in large project schedules. Capable of the same relationship assignments as other types of activities they are intricately linked into the mechanism of the schedule. Milestones are of great value to the proficient project manager and scheduler.