Two decades
ago, Japanese car-makers developed several new manufacturing methods,
including 'Just-in-Time'.
Based on the theory that most in-process inventory spends most of its
time in a buffer, waiting to be processed, Just-in-Time
scheduling dramatically reduced inventory, which coincidentally reduced
the amount of time it took product to move through a manufacturing
plant.
In the 1980's, Dr. Eli
Goldratt publicized the Theory of Constraints, which improved upon
Just-in-Time methodologies, and in the 1990's, Goldratt adapted the
Theory of Constraints to project management in his book "Critical Chain".
Based on the idea that individual estimates of project time must be
padded to allow for contingencies, Goldratt demonstrated that padded
project time operates in the same manner as inventory buffers to delay
projects.
It's Okay to be Late
The fundamental concept
behind the Theory of Constraints is that elements of a project must
be scheduled based on the average time they will take to accomplish,
not the maximum time they might take to accomplish. A project
buffer is placed at the end of the project, which allows for some
activities to be late.
Of course, it's human nature to estimate time based on
the worst case scenario, not average time to complete. As soon as
people are penalized for estimating average time and then not meeting
the estimate, they will revert to estimating the maximum time, and
project schedules will again fill up with padded time estimates.
Thus, in a project using Theory of Constraints, it is important that it
is 'okay' to be late.
It may be hard to buy at first, but even though it's
okay for individual elements to be late, Theory of Constraints project
management makes it far easier to assure that the overall project is
completed on time.
Last
Planner
The
Lean Construction Institute
has developed an effective project management technique for construction called 'Last
Planner System'. This is a deceptively simple system which
involves having foremen (last planners) planning activities for the
immediate future, using only two rules:
1. If it
can't be done, then don't plan to do it.
2. If you plan
to do it, then get it done.
These two
simple rules, along with a similar set of rules for the period after the
immediate future, have led to enormous productivity increases in
construction. For more on this, follow this link:
Lean Construction
Institute.
