The number: annualized driver-out loaded miles divided by total US truckload loaded miles (~180 billion/yr, held fixed). "Driver-out" means nobody in the cab is responsible for driving; miles with a safety driver or observer are excluded, even when the software is doing the work. That is the strictest definition, because it measures displaced driver-work.

The numerator is built operator by operator from public disclosures: trucks in driver-out service times average annual loaded miles, with utilization assumptions by operating model (long-haul lanes 60-100K mi/truck/yr; industrial short-haul from disclosed driverless hours; middle-mile from driverless order counts). Where a range is plausible, the lower bound is used.

Self-improving roster: the operator list is not fixed. Every daily update re-discovers who is running driver-out freight, including OEM-owned carriers (Volvo Autonomous Solutions holds its own carrier authority) and customer-owned fleets (Atlas, Detmar), counted once under the operating fleet. Operators still running safety drivers, like VAS today, contribute zero until the driver comes out.

Updating: history is a fixed modeled baseline anchored to milestone dates. Only the current month's point is re-estimated daily from the freshest disclosures, with a one-line basis note above. Confidence is order-of-magnitude: the trend is more reliable than the level, and it is always a modeled estimate, never an official statistic.