Schedule Compression and Time-Cost Trade-Off - Construction Project Scheduling and Control - page 226

Overtime costs more per hour and, according to the studies mentioned previously,
might contribute to lower productivity. This fact does not automatically disqualify
overtime as a means of accelerating projects. However, all of the pros and cons should
be considered before a decision is made to use this method.
Acquiring more workers and equipment may lead to site congestion and less effi-
ciency. In addition, it may create a problem for the human resources and equipment
departments: what to do with excess resources after the peak need ends.Hiring a
second and possibly a third shift may lead to more turnover time, result in more com-
munication problems, and require more careful management coordination. Extended
work hours, because of the second and possibly the third shifts, may require artificial
lighting or special nighttime arrangements (e.g., services and security). In addition,
second and third shifts may also create a problem for the human resources department:
again, what to do with them after the peak need ends.
Acquiring special materials or more efficient equipment must be evaluated on its
merits on a case-by-case basis. Such acquisition almost always costs more, but the
contractor must look at the cost-benefit ratio and other related factors (e.g., public
relations, customer satisfaction, and long-term impact). A classic case is when the con-
tractor owns expensive equipment (e.g., an excavator) that is not the most efficient for
the job. He or she is faced with the decision to use it, even though it is not the most
efficient for the job, or to acquire a more efficient piece of equipment at an extra cost.
The market is full of materials, equipment, tools, software, and other gadgets that
supposedly make work simpler, faster, or more efficient. All of these products come
with a cost that may or may not be justified.
Tip Box 8.2
Project acceleration is a science. It is not the random accumulation of resources on
the job site!
Effect of Acceleration on Direct Costs
As explained previously, direct costs almost always increase during project acceleration.
However, the more we accelerate, the more the cost of accelerating per day increases.
There are two reasons for this phenomenon:
1. At the activity level, accelerating becomes more difficult and may require dif-
ferent and more expensive techniques. Consider a CIP (cast-in-place) concrete
suspended slab activity. Its normal duration is 12 days, but we want to com-
press it to 6 days. Assume that this activity includes setting up the formwork,
placing the rebar, placing (pouring) the concrete, finishing the slab, stripping
down the forms and reshoring, and removing the reshores. Compressing the
schedule from 12 days to 11 days may be achieved with a simple and inex-
pensive adjustment, such as having a special concrete mix (with accelerators)