40 CFR § 1037.5 - Excluded vehicles.
Except for the definitions specified in § 1037.801, this part does not apply to the following vehicles:
(d) Medium-duty passenger vehicles and other vehicles subject to the light-duty greenhouse gas standards of 40 CFR part 86. See 40 CFR 86.1818 for greenhouse gas standards that apply for these vehicles. An example of such a vehicle would be a vehicle meeting the definition of “heavy-duty vehicle” in § 1037.801 and 40 CFR 86.1803, but also meeting the definition of “light truck” in 40 CFR 86.1818-12(b)(2).
(e) Vehicles subject to the heavy-duty greenhouse gas standards of 40 CFR part 86. See 40 CFR 86.1819 for greenhouse gas standards that apply for these vehicles. This generally applies for complete heavy-duty vehicles at or below 14,000 pounds GVWR.
(f) Aircraft meeting the definition of “motor vehicle”. For example, this would include certain convertible aircraft that can be adjusted to operate on public roads. Standards apply separately to certain aircraft engines, as described in 40 CFR part 87.
(h) Trailers meeting one or more of the following characteristics:
(3) Trailers with a gap of at least 120 inches between adjacent axle centerlines. In the case of adjustable axle spacing, this refers to the closest possible axle positioning.
(4) Trailers built before January 1, 2018.
(5) Note that the definition of “trailer” in § 1037.801 excludes equipment that serves similar purposes but are not intended to be pulled by a tractor. This exclusion applies to such equipment whether or not they are known commercially as trailers. For example, any equipment pulled by a heavy-duty vehicle with a pintle hook or hitch instead of a fifth wheel does not qualify as a trailer under this part.
(i) Where it is unclear, you may ask us to make a determination regarding the exclusions identified in this section. We recommend that you make your request before you produce the vehicle.