Resource Availability

A person working an 8-hour shift is not actually processing work for all 8 hours. Breaks, meetings, administrative tasks, waiting for approvals, and other interruptions reduce the time available for productive work. Resource availability captures this as a percentage.

When availability is applied, the “real” process metrics become “apparent” metrics: apparent process time increases, apparent process rate decreases, and apparent capacity decreases.

Small, less visible availability losses, waiting for an approval, brief interruptions, system delays, are often the worst ones because they’re overlooked and they add up.

Formula

Apparent Process Rate: ra = r × availability

Apparent Process Capacity: µa = µ × availability

Apparent Process Time: pa = p / availability

Example

A clerk has a process time of 6 minutes (r = 10/hour, µ = 10/hour). Resource availability is 75%. Apparent rate = 10 × 0.75 = 7.5/hour. Apparent capacity = 7.5/hour. Apparent process time = 6 / 0.75 = 8 minutes.

The actual work still takes 6 minutes, but because the clerk is only available 75% of the time, it effectively takes 8 minutes per unit from the process perspective.

Why It Matters

Availability issues at the bottleneck are critical, a reduction there directly reduces the capacity of the entire process. At non-bottleneck steps, reduced availability may not matter if there’s sufficient excess capacity. When measuring process performance, always use apparent (after-availability) figures to get an accurate picture of what the process can actually deliver.