The process velocity Lean Six Sigma metric is used in Value Stream Analysis to indicate the responsiveness or flexibility of the process to customer demand. A long lead time results in slow velocity. To calculate process velocity, use the formula below.
For example, if there are five value-added process steps in a purchasing process with a lead time of twenty hours, then the Velocity may be calculated as 5 divided by 20 equals 0.25 steps per hour.
Lead time is reduced, and velocity increased, when Work in Progress is reduced. The rationale is simple: new orders from customers cannot be started until work (or items) in process is completed. Thus, the activity on new items is stalled. An example from a service process is a physician waiting room. The patients are Work in Progress. New patients are not serviced by the doctor until those that arrived earlier are completed.
Learn more about the Lean Six Sigma principles and tools for process excellence in Six Sigma Demystified (2011, McGraw-Hill) by Paul Keller, in his online Lean Six Sigma DMAIC short course ($249), or his online Green Belt certification course ($499).