Figure 9-11.Lead on start of a preceeding activity.
completed. This type of overlap is known as a lag. It
is also a common occurrence that both the start and
the finish of two activities maybe linked, but, in this
case, they are accommodated by a combination of
lead and lag.
As seen in figure 9-11, a lead (or partial start) is
indicated by drawing the connector from the start of
the preceding activity (1). In figure 9-12, a lag (or
partial finish) is indicated by drawing the connector
from the end of the following activity (3). The values
may be given in the basic time units of the project, as
with a delay, or as a percentage of overlap. In certain
circumstances, they can be stated as quantities if the
performance of the activity can be measured on a
The indication of the type and
amount of delay, lead, or lag is generally referred to as
a lag factor.
In figure 9-11, Activity 3 may start when Activity
1 is 1-day completed, although Activity 2 must wait
for the final completion of Activity 1. In figure 9-12,
Activity 3 may start when Activity 2 is completed but
will still have 1 day to go when Activity 1 is
completed. The last phase of Activity 3 may not
begin until Activity 1 has been completed. In
figure 9-13, Activity 2 may start when Activity 1 is
Figure 9-12.Lag on finish a of following activity.
Figure 9-13.Start and finish lags on same activity.
advanced 3 days but will still have 4 days of work left
when Activity 1 is completed.
SPLITTING CONNECTORS. The number of
sequencing connectors becomes large when a net work
is of a great size.
When two activities are remote
from each other and have to be connected, the lines
tend to become lost or difficult to follow. In such
cases, it is not necessary to draw a continuous line
between the two activities. Their relationship is
shown by circles with the following-activity number
in one and the preceding-activity number in the other.
In figure 9-14, both Activities 2 and 6 are dependent
upon Activity 1.
DIRECT LINKING USING AN EVENT.
When the number of common preceding and
succeeding activities in a particular complex is large,
as in figure 9-15, a dummy event or focal activity of
zero duration may be introduced to simplify the
network. The use of such a dummy event is shown in
figure 9-16, which is a simplification of figure 9-15.
Although the effect in terms of scheduling is the
same, the introduction of the dummy improves the
clarity of the diagram.
JOINING CONNECTORS. In many in-
stances, there are opportunities to join several
Figure 9-14.Splitting connectors.