Waiting Time is any period during which a product, operator or resource is idle because something else has not yet happened. It is one of the eight wastes and one of the largest single sources of lead time, often accounting for over 90% of the total elapsed time from raw material to finished product.
Products wait in queues between stations. Operators wait for machines to finish. Machines wait for operators to load them. Everything waits for a changeover to complete. Assemblies wait for parts to arrive. Finished goods wait for inspection or shipping. Each source of waiting is a specific target for improvement.
Waiting time is invisible on most local metrics. A station reports its cycle time as 60 seconds, but doesn't report that the product waited two hours in the queue before that cycle. Utilization is high, but the utilization is on inventory nobody yet wants. Waiting shows up only in system-level metrics: lead time, flow efficiency, throughput time.
Small batches shrink queues. Balanced cycle times prevent bottlenecks that create waiting downstream. Pull scheduling prevents overproduction that creates waiting upstream. Cellular layouts eliminate inter-departmental transport waits. Setup reduction eliminates the wait for changeover. Every lean tool ultimately reduces some form of waiting.
Waiting is the largest, most hidden and most attackable waste in most factories. Measuring it honestly, and treating every hour of waiting as a specific opportunity, is one of the highest-return activities a continuous improvement program can pursue.
