Because of this abstraction, installation crews rarely have
the data they need to optimally schedule and thus execute their
work. They must rely on the numerous assumptions that are
embedded in pre-construction schedules. How much of a
problem this creates depends on the extent to which
uncertainties in their supply manifest themselves during project
execution. If pre-construction schedules were well thought-out
and steps preceding installation had no uncertainty in duration
or execution quality associated with them, then matching would
be easy. In practice, unfortunately, this is not the case. Many
projects are executed on a fast track, so construction starts
before design has been completed or materials deliveries have
been properly sequenced. Installation crews and equipment are
often kept waiting because delays in materials supply and delays