The 200,000-Hour Convention
All three OSHA-style rates use a 200,000-hour multiplier. The number is derived as 100 employees × 40 hours per week × 50 weeks per year. The result of any of these formulas is the rate per 100 full-time-equivalent workers per year.
Hours worked is the actual hours worked by all employees during the period — straight time and overtime. Hours paid for vacation, sick leave, holidays, and other non-work time are not included. For salaried staff whose hours are not tracked, the employer estimates using a standard schedule (e.g., 2,000 hours per year per FTE).
Why 200,000: The convention puts rates on a meaningful scale. A TRIR of 1.0 means one recordable case per 100 FTEs per year. A TRIR of 5.0 means five. Smaller numbers are more comparable than raw counts, which depend heavily on company size.
TRIR — Total Recordable Incident Rate
TRIR = (Total recordable cases × 200,000) / Total hours worked
The numerator is the total number of recordable cases for the period — every case appearing on the 300 Log. This includes deaths, days-away cases, restriction or transfer cases, and other recordable cases. Each case counts once regardless of severity.
TRIR is the most common headline figure. It appears on the 300A summary, in BLS reporting, on contractor prequalification forms, and in safety scorecards. Industry-specific benchmarks vary widely — heavy construction may average above 3.0 while professional services average well under 1.0.
Worked example: An establishment recorded 4 cases on its 300 Log for 2025 and its employees worked a combined 487,500 hours. TRIR = (4 × 200,000) / 487,500 = 1.64.
DART Rate — Days Away/Restricted/Transferred
DART rate = (DART cases × 200,000) / Total hours worked
The DART numerator counts only cases that involved one or more days away, restricted work, or job transfer. Cases recorded as “other recordable” do not count in DART. A case that produced both days away and restricted days counts once.
DART is the rate that most directly tracks operationally meaningful injuries. A TRIR of 2.0 driven by minor prescription medication cases looks different from a TRIR of 2.0 driven by repeated days-away cases. DART separates the two.
Worked example: Of the 4 recordable cases above, 2 involved restricted work and 1 involved days away. DART = (3 × 200,000) / 487,500 = 1.23.
LTIR — Lost Time Incident Rate
LTIR = (Cases with days away × 200,000) / Total hours worked
LTIR — sometimes called the Lost Time Case Rate — counts only cases that produced one or more days away from work. Restricted-work and transfer cases without days away do not appear in LTIR.
LTIR is favored by underwriters and many international reporting frameworks because it isolates severity. A high TRIR with low LTIR suggests aggressive case management with effective return-to-work programs. A high LTIR suggests serious injuries that prevented work even with accommodation.
Worked example: Of the 4 cases, 1 involved any days away. LTIR = (1 × 200,000) / 487,500 = 0.41.
Severity Rate
Severity rate = (Total days away × 200,000) / Total hours worked
The severity rate measures the volume of lost days rather than the count of cases. A single case with 50 days away contributes more to severity than ten cases with one day each, even though the count rates would give the opposite impression. Severity rates are helpful when comparing programs that handle a similar volume of cases differently — light-duty programs that shift days from “away” to “restricted” lower severity even when the underlying case count is unchanged.
Benchmarking Against the BLS
The Bureau of Labor Statistics publishes industry rates by 6-digit NAICS code in its annual Survey of Occupational Injuries and Illnesses. The published rates use the same 200,000-hour convention and are directly comparable to an establishment's own TRIR, DART, and LTIR.
Practical use of BLS data:
- Identify the 6-digit NAICS that best matches the establishment.
- Pull the rates for the most recent year published.
- Compare TRIR, DART, and LTIR side by side. A site above industry on TRIR but below on DART is over-recording minor cases or has effective light-duty handling — both possibilities warrant review.
- Account for workforce composition. An establishment with a high proportion of office workers will skew lower than the published industry rate even if its field operations are average.
Contractor Prequalification Thresholds
Major owners and prime contractors set TRIR thresholds for subcontractor eligibility. Common cutoffs in heavy industry, energy, and construction:
- TRIR ≤ 1.0 for prime contractor work
- TRIR ≤ 1.5 for sub-tier contractor approval
- TRIR ≤ 2.5 as a soft cap with management review
- EMR (Experience Modification Rate) ≤ 1.0
These thresholds are not standardized — each owner publishes its own. They typically combine TRIR with EMR, fatality history (typically a three-year look-back), and OSHA citation history. Subcontractor prequalification platforms (ISNetworld, Avetta, PEC Premier, BROWZ) automate the comparison.
Relationship to EMR
Experience Modification Rate is calculated by the workers' compensation rating bureau (NCCI in most states) using actual claim history. It is not directly derived from the OSHA 300 Log. EMR captures both frequency and severity of paid claims, weighted by industry-specific expected losses.
However, recordable cases and EMR claims overlap substantially. A high TRIR almost always correlates with a high EMR over a multi-year window. Recordkeeping decisions that affect case counts will eventually flow into EMR through claim filings, and EMR has a direct multiplicative effect on workers' compensation premiums — an EMR of 1.20 means a 20 percent surcharge on the manual premium.
Common Mistakes
Including paid leave in hours worked. Hours worked is actual hours on the job. Vacation, sick, and holiday hours are not included.
Counting days instead of cases for TRIR or DART. The TRIR and DART numerators are case counts. Days counts are used in the severity rate.
Mixing rates and counts when comparing periods. A site with twice the headcount can have twice the case count with the same rate. Compare rates, not raw counts, across periods or sites.
Calculating TRIR using only days-away cases. TRIR includes every recordable case, not only those with lost time.
Comparing internal rates against the wrong NAICS. A logistics warehouse should compare against warehousing NAICS, not against general transportation. Specificity changes the benchmark significantly.