Take the Path that is Really Critical - article

The traditional CPM has its place, but for most organizations it is time resources be fully recognized as part of the formula. In resource-loaded schedules, high over-allocations may force the project manager to extend the schedule in order to accommodate the resources. This creates Total Slack numbers on some activities that do not represent real a real buffer to compensate for slippages and the traditional Critical Path Method produces a path that may not drive the schedule finish date. Instead, organizations should identify the Resource-Critical Path in such schedules that looks at logical and resource dependencies in their schedules. The Resource-Critical Path is the path that is really critical because:

• The Resource-Critical Path is the true path that drives the project end date.
• When crashing a schedule, workload problems may be created if one's only focus is on the Critical Path instead of the Resource-Critical Path.
• A small change may lead to a big slippage (domino-effect) in the resource dependencies; One cannot realize this if you only look at logical dependencies.
• There is a huge cost involved with erratic workloads; the Resource-Critical Path allows you to smooth workloads.