The formulas
| Measure | Formula | Counts |
|---|---|---|
| LTIFR | (lost time injuries × 1,000,000) ÷ hours worked | Injuries causing at least one full shift lost |
| TRIFR | (recordable injuries × 1,000,000) ÷ hours worked | Lost time + restricted work + medical treatment injuries |
| US TRIR | (recordable injuries × 200,000) ÷ hours worked | Same injuries, per 100 full-time workers |
Australia and New Zealand use one million hours; the US OSHA rate uses 200,000, so the two are not directly comparable (multiply TRIR by five to approximate TRIFR).
A worked example
A site worked 480,000 hours in the year with two lost time injuries, one restricted work injury and three medical treatment injuries. LTIFR = 2 × 1,000,000 ÷ 480,000 = 4.2. TRIFR = 6 × 1,000,000 ÷ 480,000 = 12.5.
What counts
A first aid injury (a dressing, an ice pack) is not recordable. A medical treatment injury needs treatment beyond first aid. A restricted work injury means the person could not do their normal job. A lost time injury means at least one full shift away. Definitions follow AS 1885.1 in Australia; sites should write theirs down and apply them consistently, because small differences in classification move the rate more than real changes in safety do.
The limits of frequency rates
- They are lagging: they count harm after it happens.
- They are noisy at small sites: one injury in 100,000 hours is a TRIFR of 10.
- They reward under-reporting and punish honesty.
- They say nothing about the control of fatal risks; a site can have a falling TRIFR and a rising chance of a fatality.
They belong on the board with leading indicators beside them: hazards reported, safety observations completed, actions closed on time, critical control verifications done.
TRIFR and LTIFR inside daily management
The S in SQDCP on a tier board is usually days since the last recordable injury at Tier 1, with TRIFR and the leading indicators at Tier 2 and Tier 3. The daily conversation is about the leading measures and open actions; the frequency rates are reviewed monthly for trend. A recordable injury triggers an investigation whose actions appear on the same board.