The encyclopedia · Engineering & Operations · Technical decision · 1957–1958
DuPont's critical path and the Navy's PERT found the chain that sets a project's length
In 1957-58 DuPont's CPM and the U.S. Navy's PERT mapped tasks as a network and identified the critical path, so managers knew exactly which delays matter.
DuPont
the move
Big projects like chemical-plant turnarounds, submarines and later software contained thousands of interlocking tasks, so scheduling was a manager's guess against a calendar rather than an analysis of what depended on what.
In 1957 DuPont invented the Critical Path Method for scheduling maintenance shutdowns; in 1958 the U.S. Navy developed PERT, with probabilistic durations, for the Polaris program. Both model a project as a network of activities connected by dependencies.
The insight was that a project's duration equals the longest path through that network. Most activities have slack — delaying them would not change the finish. Only the critical path matters, so that is where management effort and resources must go.
Managers stopped trying to speed up everything and concentrated on the handful of tasks that decided the date. The network also made dependencies explicit, revealing relationships no one had written down.
why it works
- Dragging every task wastes money; only the longest chain determines the finish, so only it needs acceleration.
- The network makes dependencies explicit, so you stop planning against relationships you never saw.
- Slack on non-critical tasks is free float you can trade for cost or risk.
- Probabilistic durations (PERT) give an honest range instead of a single fake date.
what transfers
Do not accelerate everything; find the critical chain that sets delivery and push only there. All the other slack is time you can borrow without moving the date.
what came after
CPM and PERT became the standard for planning big builds, launches and shutdowns, later feeding into the work-breakdown structure and modern project-management tools. They remain the basis of schedule management in engineering and logistics.
references
- Project Management Fundamentals: A scant history of project management
- Project network models past, present - future
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