(a) Manufacturers may elect to participate in the voluntary in-use testing program by notifying the Administrator in writing of their intent to conduct emissions testing on in-use engines prior to the beginning of each model year. The notification must include a list of engine families the manufacturer has selected to include in the testing program.

(b) Each engine family included in the voluntary in-use testing program is exempted from the Production Line Testing requirements according to §90.701(c) for two model years, the current model year and the subsequent model year. Manufacturers may only include up to twenty percent of their eligible engine families in this in-use testing program each model year.

(c) The manufacturer must randomly select or procure a minimum of three engines, from each family included in the voluntary program, for emissions testing. These three engines may be selected or procured from:

(1) Existing consumer or independently owned fleets,

(2) Existing manufacturer owned fleets, or

(3) The production line and placed into either manufacturer or consumer owned fleets. Although a minimum of three engines must be emissions tested from each engine family in this testing program, a manufacturer may elect to emissions test more than three engines per family.

(d) The manufacturer or the manufacturer's designee must:

(1) Age the selected engines in equipment representing the top 50 percent, by production, of available equipment for the engine family.

(2) Age the selected engines to at least 75 percent of each engines' useful life as determined pursuant to §90.105.

(3) Age the engine/equipment combination in actual field conditions encountered with typical use of the equipment as described in the owner's manual or other literature sold with the equipment or engine.

(e) Documents obtained in the procurement or aging process must be maintained as required in §90.121.

(f) The manufacturer must complete testing within three calendar years from the time they notified the Administrator of their intent to participate in the voluntary in-use testing program, unless otherwise approved by the Administrator; the Administrator will give such approval upon acceptance of documentation demonstrating that appropriate in-use testing will take a longer period of time.