Regulatory subcategory means the sub-groups in each regulatory category to which mandatory fuel consumption standards and requirements apply as specified in 40 CFR 1036.230 and 1037.230 and are defined as follows:
(1) Heavy-duty pick-up trucks and vans.
(2) Vocational vehicle subcategories have 18 separate vehicle service classes as shown in Tables 1 and 2 below and include vocational tractors. Table 1 includes vehicles complying with Phase 1 standards. Phase 2 vehicles are included in Table 2 which have separate subcategories to account for engine characteristics, GVWR, and the selection of duty cycle for vocational vehicles as specified in 40 CFR 1037.510; vehicles may additionally fall into one of the subcategories defined by the custom-chassis standards in § 535.5(b)(6) and 40 1037.105(h). Manufacturers using the alternate standards in § 535.5(b)(6) and 40 CFR 1037.105(h) should treat each vehicle type as a separate vehicle subcategory.