Duration-Based Project Planning

Which came first, the chicken or the egg?  Some might think resolving this conumdrum is equivalent to deciding the best approach to building a project schedule.  Which is better, building a schedule based on resource availability or fixed (time) durations?  But, unlike the first question, the second yields a clearly superior approach.

Resource-Driven Durations

“Resource-driven durations” is when activity durations are calculated based on the availability of resources.  Unfortunately, this approach does not involve the actual team members’ commitment/accountability for activity durations and are often inaccurate due to:

• Other resource commitments not accounted for in the system.
• The durations of some activities that might be relatively fixed and not determined by resource requirements/availability.
• Software (e.g. Microsoft Project) that potentially changes the activity durations every time the schedule is re-calculated, leading to a highly unstable schedule.

Fixed Durations

For these reasons, we ascribe to using “Fixed durations” – when the team member is responsible for managing the activity estimates, while taking resource requirements/availability into consideration.  It is not an overstatement to say this approach is infinitely better in that:

• It builds team commitment/accountability for activity durations.
• Duration estimates tend to be more accurate, because the activity manager considers all factors affecting the duration.
• Microsoft Project does not change the estimated duration, and a revised duration estimate can be entered manually if needed.
• This approach maintains a stable schedule.