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1-6 Safety Metrics

A very important part of any safety program is measuring the safety program effectiveness. This is done using safety metrics. Each company must identify metrics that are effective for its operations. These metrics are not universal, will change between companies and even plant sites, and will change with time.

Metrics are usually measured over a period of time and at multiple plant sites to identify any important changes or trends. Adverse changes in the metrics will trigger a management review, with resulting recommended changes for improvement.

Figure 1-3 shows the accident pyramid demonstrating the relationship between various levels of accidents based on severity. The severity level increases toward the top of the pyramid. Accidents of lower severity occur more frequently. Indeed, for every fatality, there are orders of magnitude more accidents of lesser magnitude and even more near misses. A near miss is an accident with no consequences that might have resulted in a catastrophe if conditions had been slightly different. Accidents of smaller magnitude and higher frequency, in particular near misses, provide many opportunities to recognize problems and make improvements—and, one hopes, to prevent more consequential accidents.


Figure 1.3 The accident pyramid showing the relationships between various levels of accidents. Metrics near the top are more leading; metrics toward the bottom are more lagging.

The problem with the accident pyramid is that the items listed are all lagging indicators. That is, the accident pyramid is based on incident outcome metrics derived after an accident or near miss has already occurred. It would be preferable to have leading indicators—that is, metrics that measure activities prior to the occurrence of an accident. Lagging metrics have historically been used more often than leading metrics because they are easier to identify and interpret, and typically must be reported to various regulators. By comparison, leading metrics are more difficult to identify and interpret.

Table 1-5 lists examples of leading and lagging metrics suitable for a chemical plant. The metrics at the top of Table 1-5 are leading indicators, while the ones at the bottom are lagging indicators. Notice that process safety culture—a leading metric—is at the very top of the table, while serious injuries and fatalities—lagging metrics—are at the bottom.

Table 1-5 Example Leading and Lagging Metrics for a Chemical Plant

Leading metrics - towards top of table

Process safety culture:

Number of monthly process safety suggestions

Response time for process safety suggestions to be addressed

Number of open recommendations

Process safety budget reduction

Number of meetings addressing process safety

Time to complete an incident investigation and issue a report

Attendance at required safety meetings

Signs of worker fatigue


Percentage of workers who require remedial training

Percentage of near-miss incidents with training root causes

Change in training budget

Number of workers with overdue training

Training sessions canceled or postponed

Operating procedures:

No system to gauge whether procedures have been followed

Number of operating procedures updated per year

Number of incident investigations that recommend changes to procedures

Percentage of procedures that are annotated in the field

Tolerance of failure to follow operating procedures

Fraction of operators who believe that procedures are current and accurate

Number of procedures that are past due for review

Operators appear unfamiliar with procedures or how to use them

Maintenance procedures:

Number of overdue maintenance tasks

Number of unplanned repair work orders each month

Work order backlog

Change in maintenance budget

Number of work orders that apply to equipment that no longer exists at the site

Number of maintenance employees who hold required certification

Number of management of change (MOC) requests

Follow-up time on recommended actions

Inspection frequency

Safety system demands

Inspections with results outside limits

Excursions on safe operating limits

Near misses

Number of incidents

Property damage

Community response actions

Loss of primary containment (LOPC) incidents

First aid incidents

Minor injuries

Serious injuries


Lagging metrics - towards bottom of table

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