Leading and Lagging Indicators in Process Safety Management

Culture and Compliance

We are starting a new series of paid posts. In the series we discuss the topics of Lagging Indicators and Leading indicators as applied to process safety management (PSM).

Introduction

Companies in the process and energy industries need to know not only how safe they have been, but also how safe they are likely to be in the future. This is where the concepts of leading and lagging indicators come in.

Lagging indicators analyze past events. They are reactive — they show where systems failed. Leading indicators measure conditions, behaviors, or processes that help predict and prevent incidents before they occur. Lagging indicators show consequences and trends; leading indicators provide actionable early warnings.

Lagging indicators identify barriers that failed. Leading indicators identify the barriers that are weakening.

A Brief Example

At one refinery, the backlog of safety-critical inspections increased by 40 percent over six months. Maintenance resources were redirected to production priorities. Shortly afterward, a heat exchanger tube bundle ruptured, releasing hot hydrocarbon vapor. The inspection backlog had been a leading indicator of eroding integrity; the rupture became a lagging indicator confirming failure.

This linkage between early signs of weakness and the final event illustrates why both forms of measurement are essential. A well-designed system tracks both, converts them into trends, and acts before weak signals become major incidents.

The Process Safety Elements

To structure the discussion, we will use the elements of process safety as defined by the CCPS (The Center for Chemical Process Safety). The elements are: