Section 1037.230 - Vehicle families, sub-families, and configurations(a) For purposes of certifying your vehicles to greenhouse gas standards, divide your product line into families of vehicles based on regulatory subcategories as specified in this section. Subcategories are specified using terms defined in § 1037.801 . Your vehicle family is limited to a single model year.(1) Apply subcategories for vocational vehicles and vocational tractors as shown in table 1 of this section. This involves 15 separate subcategories for Phase 2 and later vehicles to account for engine characteristics, GVWR, and the selection of duty cycle for vocational vehicles as specified in § 1037.510 ; vehicles may additionally fall into one of the subcategories defined by the custom-chassis standards in § 1037.105(h) . Divide Phase 1 vehicles into three GVWR-based vehicle service classes as shown in table 1 of this section, disregarding additional specified characteristics. Table 1 follows: Table 1 of § 1037.230 -Vocational Vehicle Subcategories
| Engine cycle | Light HDV | Medium HDV | Heavy HDV |
| Compression-ignition | Urban | Urban | Urban. |
| Multi-Purpose | Multi-Purpose | Multi-Purpose. |
| Regional | Regional | Regional. |
| Spark-ignition | Urban | Urban | |
| Multi-Purpose | Multi-Purpose | |
| Regional | Regional | |
(2) Apply subcategories for tractors (other than vocational tractors) as shown in Table 2 of this section. (i) For vehicles certified to the optional tractor standards in § 1037.670 , assign the subcategories as described in § 1037.670 .(ii) For vehicles intended for export to Canada, you may assign the subcategories as specified in the Canadian regulations.(iii) Table 2 follows: Table 2 of § 1037.230 -Tractor Subcategories
| Class 7 | Class 8 |
| Low-roof tractors | Low-roof day cabs | Low-roof sleeper cabs. |
| Mid-roof tractors | Mid-roof day cabs | Mid-roof sleeper cabs. |
| High-roof tractors | High-roof day cabs | High-roof sleeper cabs. |
| Heavy-haul tractors (starting with Phase 2). |
(b) If the vehicles in your family are being certified to more than one FEL, subdivide your greenhouse gas vehicle families into subfamilies that include vehicles with identical FELs. Note that you may add subfamilies at any time during the model year.(c) Group vehicles into configurations consistent with the definition of "vehicle configuration" in § 1037.801 . Note that vehicles with hardware or software differences that are related to measured or modeled emissions are considered to be different vehicle configurations even if they have the same modeling inputs and FEL. Note also, that you are not required to separately identify all configurations for certification. Note that you are not required to identify all possible configurations for certification; also, you are required to include in your final ABT report only those configurations you produced.(d) You may combine dissimilar vehicles into a single vehicle family in special circumstances as follows: (1) For a Phase 1 vehicle model that straddles a roof-height, cab type, or GVWR division, you may include all the vehicles in the same vehicle family if you certify the vehicle family to the more stringent standard. For roof height, this means you must certify to the taller roof standards. For cab-type and GVWR, this means you must certify to the numerically lower standards.(2) For a Phase 2 or later vehicle model that includes a range of GVWR values that straddle weight classes, you may include all the vehicles in the same vehicle family if you certify the vehicle family to the numerically lower CO2 emission standard from the affected service classes. Vehicles that are optionally certified to a more stringent standard under this paragraph (d)(2) are subject to useful-life and all other provisions corresponding to the weight class with the numerically lower CO2 emission standard. For a Phase 2 or later tractor model that includes a range of roof heights that straddle subcategories, you may include all the vehicles in the same vehicle family if you certify the vehicle family to the appropriate subcategory as follows: (i) You may certify mid-roof tractors as high-roof tractors, but you may not certify high-roof tractors as mid-roof tractors.(ii) For tractor families straddling the low-roof/mid-roof division, you may certify the family based on the primary roof-height as long as no more than 10 percent of the tractors are certified to the otherwise inapplicable subcategory. For example, if 95 percent of the tractors in the family are less than 120 inches tall, and the other 5 percent are 122 inches tall, you may certify the tractors as a single family in the low-roof subcategory.(iii) Determine the appropriate aerodynamic bin number based on the actual roof height if you measure a CdA value. However, use the GEM input for the bin based on the standards to which you certify. For example, of you certify as mid-roof tractors some low-roof tractors with a measured CdA value of 4.2 m2, they qualify as Bin IV; and you must input into GEM the mid-roof Bin IV value of 5.85 m2.(e) You may divide your families into more families than specified in this section.(f) You may ask us to allow you to group into the same configuration vehicles that have very small body hardware differences that do not significantly affect drag areas.81 FR 74048, Oct. 25, 2016, as amended at 86 FR 34462, June 29, 2021; 88 FR 4639, Jan. 24, 2023; 89 FR 29777, Apr. 22, 2024 81 FR 74048, 10/25/2016, as amended at 86 FR 34462, 6/29/2021; 88 FR 4639, 3/27/2023; 89 FR 29777, 6/21/2024