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TRIR, DART and LTIFR: getting the denominators right

How the TRIR denominator is built: start from gross hours paid on the payroll register, subtract paid non-work time, add agency hours you supervise day to day, and post the reconciled hours actually worked to the monthly KPI record.How the TRIR denominator is built: start from gross hours paid on the payroll register, subtract paid non-work time, add agency hours you supervise day to day, and post the reconciled hours actually worked to the monthly KPI record.

Nobody argues about the numerator. If a case is on the OSHA 300 Log, the classification debate happened months ago. The argument in the boardroom, and the finding in the audit, is almost always about the denominator: which hours you counted, where they came from, and whether anyone can reproduce them.

The TRIR formula takes ten seconds to explain. The hours behind it take a week to reconstruct if nobody built the trail on the way through. One jurisdictional note first: everything cited to 29 CFR Part 1904 below is US federal OSHA. Canadian operations report on a different basis through provincial workers' compensation boards, covered near the end.

ยง 1904.31 do you supervise them day to day? Numerator their recordable cases count Denominator their hours worked count × 200,000 = the rate Apply the test to one side only and the rate is biased, not merely wrong
One test, both halves. Counting a supervised contractor's injury while leaving their hours out of the denominator inflates the rate, and it does so in the same direction every time. Auditors call that bias.

What are the TRIR, DART and LTIFR formulas?

OSHA publishes the total recordable case rate and the DART rate in its recordkeeping forms package, on the page titled Optional Calculating Injury and Illness Incidence Rates:

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