Heavy-duty Vehicle and Engine Greenhouse Gas Emission Regulations — 18
ii) for regional vocational vehicles and incomplete vocational vehicles that are to become regional vocational vehicles of the 2021 model year or a subsequent model year that are equipped with a spark-ignition engine, (A) those vehicles that are or are to become light heavy-duty vehicles, or (B) those vehicles that are or are to become medium heavy-duty vehicles, (viii) for urban vocational vehicles and incomplete vocational vehicles that are to become urban vocational vehicles of the 2021 model year or a subsequent model year that are equipped with a spark-ignition engine, (A) those vehicles that are or are to become light heavy-duty vehicles, or (B) those vehicles that are or are to become medium heavy-duty vehicles, (ix) Class 7 low-roof tractors and incomplete tractors, (x) Class 7 mid-roof tractors and incomplete tractors, (xi) Class 7 high-roof tractors and incomplete tractors, (xii) for Class 8 tractors and incomplete tractors of the 2020 model year or an earlier model year, (A) those that are low-roof and are equipped with a day cab, (B) those that are low-roof and are equipped with a sleeper cab, (C) those that are mid-roof and are equipped with a day cab, (D) those that are mid-roof and are equipped with a sleeper cab, (E) those that are high-roof and are equipped with a day cab, or (F) those that are high-roof and are equipped with a sleeper cab, (xiii) for Class 8 tractors and incomplete tractors of the 2021 model year or a subsequent model year that have a GCWR of less than 43 998 kg (97,000 pounds), (A) those that are low-roof and are equipped with a day cab, (B) those that are low-roof and are equipped with a sleeper cab, (C) those that are mid-roof and are equipped with a day cab, (D) those that are mid-roof and are equipped with a sleeper cab, (E) those that are high-roof and are equipped with a day cab, or (F) those that are high-roof and are equipped with a sleeper cab, (xiv) for Class 8 tractors and incomplete tractors of the 2021 model year or a subsequent model year that have a GCWR of 43 998 kg (97,000 pounds) or more, but less than 54 431 kg (120,000 pounds), (A) those that are low-roof and are equipped with a day cab, (B) those that are low-roof and are equipped with a sleeper cab, (C) those that are mid-roof and are equipped with a day cab, (D) those that are mid-roof and are equipped with a sleeper cab, (E) those that are high-roof and are equipped with a day cab, or (F) those that are high-roof and are equipped with a sleeper cab, (xv) for Class 8 tractors and incomplete tractors of the 2021 model year or a subsequent model year that have a GCWR of 54 431 kg (120,000 pounds) or more, other than those that are or are to become heavy-haul tractors, (A) those that are low-roof and are equipped with a day cab, (B) those that are low-roof and are equipped with a sleeper cab, (C) those that are mid-roof and are equipped with a day cab, (D) those that are mid-roof and are equipped with a sleeper cab, (E) those that are high-roof and are equipped with a day cab, or (F) those that are high-roof and are equipped with a sleeper cab, (xvi) heavy-haul tractors and incomplete tractors that are to become heavy-haul tractors; (b) in the case of heavy-duty engines and subject to subsections (8) and (9), each fleet is composed solely of the engines referred to in one of the following subparagraphs: (i) spark-ignition engines other than heavy heavy-duty engines of the 2021 model year or a subsequent model year, (ii) light heavy-duty engines that are compression-ignition engines and that are designed to be used in vocational vehicles and incomplete vocational vehicles, (iii) medium heavy-duty engines that are compression-ignition engines and that are designed to be used in vocational vehicles and incomplete vocational vehicles, (iv) heavy heavy-duty engines that are spark-ignition engines of the 2021 model year or a subsequent model year or compression-ignition engines and that are designed to be used in vocational veh