Two regulators counted the same crashes. They disagree.
California requires collision reporting under one definition. The federal government requires it under another. Both cover the same vehicles in the same state over the same months — and the totals do not match.
The same months, counted twice
This is not evidence that anyone under-reported: the two regimes define a reportable collision differently, and that difference accounts for most of the gap.
4 further periods are on file with only one of the two regulators reporting. They are left off the chart rather than drawn against a zero the other regulator never filed.
The earlier periods come from the state’s aggregate era, when a carrier filed one collision total for the period rather than one row per collision. It is the same quantity counted more coarsely, and nothing on this page divides it. Those periods run December to February, March to May, June to August and September to November, which is why they are labelled by month rather than by quarter: matching them to a calendar quarter would compare three months against a different three.
Why the two definitions differ
The California filing counts any collision involving an occupant, pedestrian, cyclist, motorcyclist, other vehicle, rail or property — including events during passenger pick-up and drop-off, and events off the public roadway.
The federal order applies to a narrower set of circumstances and to vehicles operating under automated control at the time. A collision can therefore be genuinely reportable in one system and genuinely not in the other, with nobody having done anything wrong.
What remains after those differences are accounted for is the part worth asking about — and it is smaller than the headline gap.