User:RW1943/PRS

Origins
In 1979,Eliyahu M. Goldratt introduced the concept of Critical Chain Project Management (CCPM) in his book, Critical Chain.

Pooled Risk Scheduling (PRS) is a method of planning and managing projects that addresses task uncertainty and protects project commitment dates. Pooled Risk Scheduling is based upon the Critical Chain Project Management (CCPM) concept of buffers. It is based upon standard critical path concepts and does not require the adaption of the CCPM methodology.

In Pooled Risk Scheduling, as in CCPM, a buffer is placed at the end of a project to protect the project end date against common cause task variance. The CCPM concept of removing safety from individual task estimates and pooling it in the buffer at a reduced amount can also be applied to Pooled Risk Scheduling.

In Pooled Risk Scheduling, a Monte Carlo simulation is used to size the buffers. Resource leveling can be optionally preformed in each simulation iteration to incorporate resource constraints into the determination of the critical path and the buffer sizes. The CCPM feeding buffers are avoided by basing PRS on standard critical path methods and capitalizing on traditional float as a safety factor. Float can be reduced before a simulation through the use of start no earlier date constraints. PRS supports milestone buffer integration into the project network to protect milestone date commitments.

PRS project status tracking is performed by comparing the original buffer size with a re-estimated buffer size after each update cycle. This re-estimation is done by running a Monte Carlos simulation that leaves the original buffers intact but calculates an Expected Buffer Finish for each buffer. This Expected Buffer Finish can be logged with a date stamp and then graphically plotted as a ratio of the baseline buffer to provide time-phased insight into project performance. The ability to run a simulation on the current state of an updated PRS project while leaving the original buffers in place means that all of the changes made to task estimates, task durations, resource assignments, task additions, and task dependencies are taken into account in evaluating buffer consumption.