(a) For light-duty vehicles and light-duty trucks, intermediate useful life is a period of use of 5 years or 50,000 miles, whichever occurs first.
(b) Full useful life is as follows:
(1) For light-duty vehicles and light light-duty trucks full useful life is a period of use of 10 years or 100,000 miles, which ever occurs first.
(2) For heavy light-duty trucks full useful life is a period of use of 11 years or 120,000 miles, which ever occurs first.
(3) For complete heavy-duty vehicles, the full useful life is a period of use of 11 years or 120,000 miles, which ever occurs first.
(c) Manufacturers may petition the Administrator to provide alternative useful life periods for light-duty trucks or complete heavy-duty vehicles when they believe that the useful life periods are significantly unrepresentative for one or more test groups (either too long or too short). This petition must include the full rationale behind the request together with any supporting data and other evidence. Based on this or other information the Administrator may assign an alternative useful-life period. Any petition should be submitted in a timely manner, to allow adequate time for a thorough evaluation. For light-duty trucks, alternative useful life periods will be granted only for THC, THCE, and idle CO requirements.