40 CFR § 86.435-78 - Extrapolated emission values.
(a) If the deterioration factor lines are below the standards between the minimum test distance and the useful life, or if all points used to generate the lines are below the standards, predicted useful life emissions shall be calculated. If not, the manufacturers may elect to withdraw the vehicle or accumulate additional service.
(b) The emission test results of each pollutant obtained from the half life test will be multiplied by the appropriate deterioration factors to determine useful life emissions.
(1) If the useful life emissions are at or below the standards, certification will be granted.
(2) If any of the useful life emissions exceed the emission standards, the vehicle must (if not withdrawn) accumulate distance to the useful life.