Schedule Compression and Time-Cost Trade-Off - Construction Project Scheduling and Control - page 237

apply a filter to show only critical activities (be careful of the software's defi-
nition of critical activities ).
3. For every activity that may be accelerated, prepare a list of accelerating meth-
ods in an ascending order of cost. When the activity has to be accelerated,
start with the least expensive method till this method is exhausted then cross
it and use the next method, if you need to keep accelerating.
4. Pick an activity on the critical path and reduce its duration by one day. Sched-
ule the project (perform CPM calculations) and examine the impact on the
project's finish date. If the finish date is now 1 day earlier, move to step 6. If
you are applying a filter, you may have to refresh the view.
5. If the project finish date has not changed, at least one other critical path must
exist, and you reduced only one. Go back to the list of critical activities (those
with least total float), pick one, and repeat step 4. Looking at the different
paths on either a bar chart or a logic diagram can be helpful.
6. You have reduced the project duration by 1 day; you now need to reduce it
by another day. Repeat step 4. You may find more activities that are critical
now. This fact does not mean there will be more options for you. On the
contrary, you may have to compress several activities simultaneously to reduce
the project duration by one day.
7. Repeat the same steps until you achieve the desired duration.
8. Avoid compressing any path by multiple days in one step unless you know
the critical path is longer than the next one by at least the same number of
days or the compressed activity is shared between/among the longest paths.
For example, if you compress a path by 10 days, but the project's duration
decreases by only 3 days, you have achieved nothing from the last 7 acceler-
ated days. Only the first 3 days of acceleration were effective. In this case, go
back and replace the 10-day compression with 3 days (or the correct effective
number).
9. If you are determining the least-cost duration, you may want to do the cal-
culations manually (for every step, you calculate the total net savings by
subtracting the increase in direct costs from the decrease in indirect costs).
You may also create a simple spreadsheet that performs the calculations.
10. The project manager should give the scheduler the crash duration and crash
cost information for the activities. The scheduler must then experiment with
the accelerated schedule and submit the results to the project manager. After
the project manager approves the results, the scheduler may implement the
accelerated schedule.
POTENTIAL ISSUES WITH UNCOORDINATED PROJECT ACCELERATION
As explained earlier, the contractor may accelerate the project schedule, responding to
instructions from the owner, or the contractor may do so for his or her own interest.