Introduction

All meaningful operational improvement is rooted in flow. To manage flow effectively, organisations require metrics that reflect total system performance rather than local efficiency.

1: Metrics for Flow – Reliability

George Plossl stated that all benefits are directly related to the speed of flow of materials and information.

Flow describes how quickly materials and information move from demand to delivery. The first category of flow metrics is reliability.

Reliability answers a simple question. How well are we performing in the eyes of our customers?

The primary measure of reliability is Due Date Performance. It reflects whether the organisation delivers according to its promises and is a lagging indicator of operational control.

2: Metrics for Flow – Stability

Little’s Law states that work in progress equals flow rate multiplied by flow time.

This relationship explains why inventory and lead times are inseparable. High work in progress leads to longer flow times.

Operational stability is the ability to control how variability flows through the system. It does not eliminate variability but mitigates its impact.

A demand driven operating model based on pull principles is essential to achieving stability.

3: Metrics for Flow – Velocity

Velocity relates to flow time and is most clearly seen in cycle time from order to delivery.

In stable operating environments, cycle times naturally decrease. This is not achieved through pressure or expediting but is a by-product of improved flow.

Velocity creates competitive advantage when quality and capability are comparable.

Flow improvement follows a clear sequence. Reliability depends on stability. Velocity emerges once stability and reliability are in place.