Flaw #3 Original Durations
Usually, the OD is supposed to mean something, but I am sure that every scheduler has found out differently. A number of times I have asked the estimating department for their help in assigning OD to activities. Every time there was no such help offered and I was left to figure out the OD on my own. Fortunately, I was a general construction estimator and old fashion scheduler for more than twenty years before delving into computer generated scheduling. So, more often than not, I was capable of estimating work time with some degree of accuracy. However, no matter how accurate the OD is determined, it seldom works out in the project schedule as it relates to the Actual Duration. It is just the nature of computer generated schedules.

It is all a misunderstanding basically. The OD is only accurate within the confines of the AD. In other words, if an activity is assigned 10 work days as the OD, but the actual duration is 30 work days; the explanation is simple enough. Within the AD time frame of 30 work days, the actual physical work took 10 days to accomplish. The 10 work days were not meant to be consecutive work days, but rather intermittent work days. The computer does not understand this situation and therefore, the flaw. There are always non-work days that occur within the majority of the Actual Duration time frame. These non-work days are not considered in the Original Duration estimate. If they were, the schedule would be blown away from the start. Ultra-detailing of a work item in a series of sequential minor installation steps is not the answer. It makes the schedule too cumbersome to produce and boring to the people who try to use it. It is far simpler to percentile progress of a single work item than it is to percentile its many sequential parts when the result is the same. The flipside is to NOT make a worklist that is too generalized such that generalization makes updating the physical percent complete of an item a matter of opinion and guess-estimating instead of fact.

There is the Suspend and Resume device, but nobody ever uses it in construction work that I know of. Field personnel are not going to give up this information, mainly because they do not know the dates anyway and do not want to be bother with them. The scheduler cannot be in the field every minute to monitor every minor item that makes up the total work detail and determine when to suspend work time and then be there to resume it. There are too many different work activities in too many separate locations to be accurate enough to track progress. A project would need a small army of schedulers to have any affect and they would probably not be all that accurate anyway.