Basic Networks - Construction Project Scheduling and Control - page 39

NETWORKS VERSUS BAR CHARTS
When comparing bar charts with networks, we find that networks have three advan-
tages over bar charts:
1. Networks show logic (i.e., the relationships among activities). Bar charts do
not.
2. Networks can better represent large and complicated projects.
3. Networks can estimate, or predict, the completion date of a project, or other
dates, on the basis of mathematical calculations of the CPM.
Bar charts predict the completion of the project, or other dates, on the basis of
the user's skills. In contrast to networks, bar charts have five advantages:
1. Bar charts are time-scaled (i.e., the length of the activity bar represents the
time duration of the activity). Both nodes, in the node networks, and arrows,
in the arrow networks, are not time-scaled.
2. Bar charts are simple to prepare.
3. Bar charts are easy to understand.
4. Bar charts are more acceptable for presentations, especially for field people and
people who are unfamiliar with the CPM.
5. Bar charts can be loaded with more information, such as cash-flow diagrams
and man-hours. This advantage is partially a by-product of being time-scaled.
Tip Box 3.2
Bar charts did not vanish with the introduction of logic networks and the Critical Path
Method (CPM). It just turned from a scheduling method to a display method for project
schedules.
Effective Use of Bar Charts with CPM
Bar charts have an effective weapon that CPM networks do not have: simplicity and
power of presentation. As mentioned in item 4 in the preceding list, bar charts can be
used effectively for mainly two types of presentations:
1. Presentations to field people : The project manager produces customized reports
that include only a small group of the project activities (e.g., subcontractors'
bar charts or “look-ahead” bar charts for work activities in the next 2 weeks).
The project manager can also filter a group of activities that are to be done at
a specific area of the project or only critical activities. With the use of activity
codes and the power of computer software, there is no limit for such uses.