(a) Applicability. This program is an option available for small-volume manufacturers and small-volume test groups as described in § 86.1838.

(b) Determination of deterioration factors. No service accumulation method or vehicle/component selection method is required. Deterioration factors for all types of regulated emissions are assigned using the provisions in this paragraph (b). A separate assigned deterioration factor is required for each durability group. Manufacturers shall use good engineering judgment in applying deterioration factors. Manufacturers may use assigned deterioration factors that the Administrator determines and prescribes.

(1) The deterioration factors will be the Administrator's estimate, periodically updated and published in a guidance document, of the 70th percentile deterioration factors calculated using the industry-wide database of previously completed durability data vehicles or engines used for certification.

(2) The Administrator may use discretion to develop assigned deterioration factors using alternative methods if there is insufficient information to calculate an appropriate industry-wide deterioration factor (for example: a new engine technology coupled with a proven emission control system). These methods may include the use of assigned deterioration factors based on similar durability vehicles.

(3) Alternatively, with advance approval from the Administrator, a manufacturer may use deterioration factors developed by another manufacturer. The manufacturer seeking to use these deterioration factors must—

(i) Demonstrate that the engines from the two manufacturers share technical parameters to the degree that would support the conclusion that a common deterioration factor should apply for both vehicle configurations as defined in § 86.1803.

(ii) Provide supporting information, such as histograms of exhaust temperature data, comparisons of vehicle weight and road load horsepower, or comparisons of powertrains and emission control systems.