How the number is built, and where it stops

1. The data

FMCSA publishes the input files behind the Safety Measurement System as open datasets: inspections, violations, the carrier census, crashes. They are refreshed monthly. We download the full set, record the checksum, row count and schema of each file, and store it unchanged.

Unchanged matters. If a rule we apply later turns out to be wrong, it can only be fixed by going back to what the source actually said. So the raw files are kept as received, and every correction happens downstream of them.

2. The method

We apply FMCSA's published SMS methodology, version 3.21. The order of operations is not a detail: the severity of the violations in one inspection is summed, capped at 30, and only then multiplied by the time weight. Applying the cap the other way around changes the answer for a large share of carriers, always downward.

The arithmetic is decimal, not binary floating point, and the published figure is truncated rather than rounded. Both of these were established by comparing against FMCSA's own published values, not assumed — rounding instead of truncating would disagree with FMCSA on roughly a quarter of carriers, and always in the same direction.

3. What we can check, and what we cannot

FMCSA publishes measures for passenger carriers but not for property carriers — which is nearly everyone this product is for. So we validate where we can: we recompute the published passenger figures from the raw files and compare them against FMCSA's.

Carrying that result across to property carriers is a reasoned assumption, not a proof. It is the single largest risk in the product, and you are entitled to know it exists rather than to find it in a footnote.

4. Where we refuse to answer

A product that always produces a number is a product that sometimes produces a wrong one.

• If a carrier has no relevant inspections in the window, we say the data is insufficient. FMCSA prints a zero in that situation. A zero means "we looked and found nothing"; here nobody looked, and the two should not read the same.
• If our estimate for a BASIC does not pass its own accuracy check, the position is withheld and the reason is named. The measure and the contribution are still shown.
• If the monthly data changes shape, or arrives short, or fails a checksum, we publish nothing new and serve the previous snapshot with its date on it.
• If two independent readings of your uploaded document disagree, you see both. We do not silently pick one.

5. What happens to your documents

Documents you upload for the paid check go to encrypted storage, separate from everything used to compute scores, with an automatic deletion policy. Their contents are not written to logs.

The calculation side of the product has no access to them at all, and the personal fields in the FMCSA files — vehicle identifiers, plates, decals — are dropped before the data reaches the calculation store. That is checked automatically on every run, not by inspection.