What is a Near-Critical Path?
A near-critical path is a chain of activities with float so small that a modest slip makes it the new critical path. Managing only the critical path is driving while watching one mirror: the paths one bad week behind it are where surprises come from.
Practice sets a float threshold (say, anything under 10 days on a year-long job) and watches that whole family. Monte Carlo makes the point statistically: the "criticality index" shows how often each path turns critical across simulations.
Worked example
The critical path runs through structural steel (float 0). The mechanical package trails it at 4 days of float — near-critical. The PM manages both like they're critical, and when a steel delivery recovers three days but the chiller shipment slips five, the schedule's spine shifts to mechanical overnight. Nobody is surprised, because nobody was only watching steel.