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114 PRACTICAL SCHEDULING

equal to the length of time that it will take to perform the series of tasks that we
outline above. With hammocks, we don’t have to calculate this duration. We cre-
ate a task Set Traffic Diversion Signs and Cones. We establish a start-to-start rela-
tionship with the first guardrail task, and a finish-to-finish relationship with the
last guardrail task. The computer sets the task duration as equal to the duration of
the series of tasks that it spans.

If the work is scheduled to start on 6/1, and run until 6/22, then a duration of
three weeks is applied to the hammock task. If the duration of any of the tasks
within the chain changes, during either planning or execution, the hammock task
will automatically reflect these changes.

If there are daily costs associated with the hammock task, these are also auto-
matically calculated. So, if the signs and cones are costed at $2,000 per week, the
budget is set at $6,000. If the chain of tasks is stretched to four weeks, the budget
will change to $8,000. The same approach applies to resources that are assigned
to hammocks.

Hammocks can be stretched between any two points in the project network. It
doesn’t have to be a contiguous series of tasks, or be under the purview of a single
responsible party. Hammocks can also be used as auxiliary summary tasks, to
show the span of time between the two anchor points.

Practical Uses of the Baseline

Most CPM products have a Set Baseline function. A baseline is a snapshot of the
project schedule at a specific point in time. The early and late dates are saved, as
baseline or target dates, for later comparison to current dates, after the schedule
is updated. There should always be an Original Baseline. This is a set of project
target dates at the time that the official project schedule is accepted. As the
schedule is updated, a variance report can be produced to display the changes
from the original plan. The report can be set up to select only variances that ex-
ceed a certain threshold, and sorting can be set to order the tasks by amount of
variance (largest first).

If your product supports multiple baselines, you will want to consider these
additional baseline options. Create a new baseline (while retaining the origi-
nal) every time that there is an approved major change to the plan. I also
like to create a rolling baseline. This is a snapshot of each update as it is
closed out. When the next schedule update is performed, I compare the new
dates and float to the last set (the rolling baseline) to note variances during this
last update. Once the update is completed and reviewed, I replace the previ-
ous rolling baseline with a snapshot of the current update, ready to use for the
next round.