TRIR vs LTIFR: two safety rates, two bases

International: OSHA (United States), compared with the per-million-hours basis used in South Africa, Australia and ILO statistics.

A contractor is tendering for work with a US client. The tender form asks for its TRIR. The contractor's own monthly safety report shows an LTIFR of 4.0 and a TRIFR of 10.0. Neither number is the one the client asked for, and copying either into the form would be wrong. The two rates count different injuries, and they count them against different numbers of hours.

To work either rate out for your own site, use the free LTIFR and TRIFR calculator; it shows both bases side by side.

The two formulas

• TRIR (total recordable incident rate) = recordable cases × 200,000 ÷ hours worked
• LTIFR (lost-time injury frequency rate) = lost-time injuries × 1,000,000 ÷ hours worked

Two things change between them: the case definition on top of the fraction, and the basis that scales it.

Where 200,000 comes from

OSHA's injury and illness recordkeeping rule is 29 CFR Part 1904. OSHA gives the incidence rate formula as the number of injuries and illnesses multiplied by 200,000, divided by employee hours worked. In a 2016 letter of interpretation it explains the constant: 200,000 is the hours that 100 employees would work at 40 hours a week for 50 weeks a year. So a TRIR of 2.0 reads as "two recordable cases for every 100 full-time workers in a year".

What counts as "recordable" is set by 29 CFR 1904.7. A work-related injury or illness is recordable if it results in death, days away from work, restricted work or transfer to another job, medical treatment beyond first aid, or loss of consciousness, or if it is a significant injury or illness diagnosed by a physician or other licensed health care professional. First aid is a closed list in 1904.7(b)(5)(ii): if a treatment is not on that list, it is medical treatment.

Two details that change the number:

• OSHA's own pages call the all-cases figure the Total Case Rate. "TRIR" is the name most of industry uses for it.
• The Bureau of Labor Statistics method counts the nonfatal recordable cases from the OSHA Form 300A, and says hours worked should exclude paid time not worked, such as vacation, sick leave and holidays.

Where 1,000,000 comes from

The per-million basis is the international statistical convention. The resolution on occupational injury statistics adopted by the 16th International Conference of Labour Statisticians in 1998 defines the frequency rate as new cases divided by hours worked, multiplied by 1,000,000.

National practice follows it. Safe Work Australia publishes its frequency rates per million hours worked; the series it used to call LTIFR is now published as the workers' compensation injury frequency rate, and its "lost time claims" are claims with one day or shift or more away from work, a fatality or a permanent impairment. South Africa's Mine Health and Safety Inspectorate reports fatality and injury frequency rates per million hours worked in its annual report.

There is no single international definition of a lost-time injury. Some organisations count from the first full shift lost, some from the day after the injury, and some include restricted duty. Whatever yours is, write it down next to the rate.

A worked example

Illustrative example with made-up round numbers. One site, one year: 500,000 hours worked, 2 lost-time injuries and 3 other recordable cases (medical treatment and restricted work), so 5 recordable cases in total.

The same five people were hurt. The four numbers range from 0.8 to 10.0.

Converting between the bases

A rate per 1,000,000 hours is five times the same rate per 200,000 hours. Divide by 5 to go from per-million to OSHA's basis; multiply by 5 to go the other way.

That converts the basis only. An LTIFR of 4.0 becomes 0.8 on the 200,000-hour basis, but it is still a lost-time rate. It is not a TRIR, because a TRIR also counts medical treatment, restricted work and the other recordable categories. To produce a TRIR you need the case count as OSHA defines it, not a converted LTIFR.

Our free LTIFR and TRIFR calculator works on either basis and shows the other alongside it.

What each rate hides

1. Severity. A fracture and a sprain that needed a prescription are one case each. Neither rate tells you how badly anyone was hurt.
2. Restricted duty. Under OSHA a restricted-work case is recordable, so it stays in the TRIR. Under many lost-time definitions it is not a lost-time injury. An LTIFR can fall because injured people were placed on restricted duty rather than because fewer people were hurt. Reporting both rates side by side makes that visible.
3. Small denominators. OSHA's 2016 letter notes that one injury moves a small employer's rate far more than a large employer's, and suggests pooling three years of cases and hours. Safe Work Australia likewise suggests a longer period, such as five years, for smaller organisations.
4. The hours. Contractors in or out, estimated or actual hours, paid leave included or excluded: each choice moves the rate without a single injury changing.
5. Everything before the injury. Near misses, failed inspection items and actions that sit open for weeks never appear in either rate. OSHA's letter recommends using leading as well as lagging indicators for this reason.

Reporting both honestly

• State the basis in the label: "TRIR (per 200,000 hours)", "LTIFR (per 1,000,000 hours)".
• State the case definition, whether contractors are included, the period and where the hours came from.
• Never compare a rate on one basis with a benchmark on the other.
• When a client asks for TRIR, count recordable cases the way 29 CFR 1904.7 defines them.

Where Inspecable fits

Inspecable does not calculate your TRIR or LTIFR; the free calculator above does that. What Inspecable handles is the leading side the rates cannot see. Inspections run offline on Android at the workplace. A failed item raises a tracked issue with a severity and a due date on the spot. An action cannot close without a method, evidence and a signature, from someone other than the person it was assigned to. Every inspection carries a hash-chained history of its sign-offs and amendments that you can verify on demand, and a date range of completed inspections exports as one ZIP. See how corrective actions work.

This is a general guide, not legal advice.