Project schedules tend toward tardiness, but what can be done to make schedules more reliably on time? Schedule buffer similar to a cost contingency helps projects become more reliable.
Project plans are generally more optimistic than reality. Reasons for this disconnect are that project plans do not consider: inefficiencies in the handover of tasks between resources, workplace congestion, coordination among contributors, and the multitasking of critical resources. One would think that not accounting for these delay effects would be counter balanced by contributors padding their estimates. But this is not the case. Once a duration is entered in the project plan (whether conservative or optimistic) it becomes subject to all the drag effects of Parkinson’s Law and procrastination.
