# 49 CFR § 535.6 - Measurement and calculation procedures.

§ 535.6 Measurement and calculation procedures.

This part describes the measurement and calculation procedures manufacturers use to determine annual fuel consumption performance results. Manufacturers use the fuel consumption results determined in this part for calculating credit balances specified in § 535.7 and then determine whether they comply with standards as specified in § 535.10. Manufacturers must use EPA emissions test results for deriving NHTSA's fuel consumption performance rates. Consequently, manufacturers conducting testing for certification or annual demonstration testing and providing CO2 emissions data to EPA must also provide equivalent fuel consumption results to NHTSA for all values. NHTSA and EPA reserve the right to verify separately or in coordination the results of any testing and measurement established by manufacturers in complying with the provisions of this program and as specified in 40 CFR 1037.301 and § 535.9. Any carry over data from the Phase 1 program may be carried into the Phase 2 only with approval from EPA and by using good engineering judgment considering differences in testing protocols between test procedures.

(a) Heavy-duty pickup trucks and vans. This section describes the method for determining the fuel consumption performance rates for test groups and for fleets of complete heavy-duty pickup trucks and vans each model year. The NHTSA heavy-duty pickup truck and van fuel consumption performance rates correspond to the same requirements for EPA as specified in 40 CFR 86.1819-14.

(1) For the Phase 1 program, if the manufacturer's fleet includes conventional vehicles (gasoline, diesel and alternative fueled vehicles) and advanced technology vehicles (hybrids with powertrain designs that include energy storage systems, vehicles with waste heat recovery, electric vehicles and fuel cell vehicles), it may divide its fleet into two separate fleets each with its own separate fleet average fuel consumption performance rate. For Phase 2, manufacturers may calculate their fleet average fuel consumption rates for a conventional fleet and separate advanced technology vehicle fleets. Advanced technology vehicle fleets should be separated into plug-in hybrid electric vehicles, electric vehicles and fuel cell vehicles.

(2) Vehicles in each fleet should be selected and divided into test groups or subconfigurations according to EPA in 40 CFR 86.1819-14(d).

(3) Use the EPA CO2 emissions test results for each test group, in grams per mile, for the selected vehicles.

(i) Use CO2 emissions test results for vehicles fueled by conventional and alternative fuels, including dedicated and dual-fueled (multi-fuel and flexible-fuel) vehicles using each fuel type as specified in 40 CFR 86.1819-14(d)(10).

(ii) Use CO2 emissions test results for dual-fueled vehicles using a weighted average of the manufacturer's emission results as specified in 40 CFR 600.510-12(k) for light-duty trucks.

(iii) All electric vehicles are deemed to have zero emissions of CO2, CH4, and N2O. No emission testing is required for such electric vehicles. Assign the fuel consumption test group result to a value of zero gallons per 100 miles in paragraph (a)(4) of this section.

(iv) Use CO2 emissions test results for cab-complete and incomplete vehicles based upon the applicable complete sister vehicles as determined in 40 CFR 1819-14(j)(2).

(v) Use CO2 emissions test results for loose engines using applicable complete vehicles as determined in 40 CFR 86.1819-14(k)(8).

(vi) Manufacturers can choose to analytically derive CO2 emission rates (ADCs) for test groups or subconfigurations. Use ADCs for test groups or subconfigurations in accordance with 40 CFR 86.1819-14 (d) and (g).

(4) Calculate equivalent fuel consumption results for all test groups, in gallons per 100 miles, from CO2 emissions test group results, in grams per miles, and round to the nearest 0.001 gallon per 100 miles.

(i) Calculate the equivalent fuel consumption test group results as follows for compression-ignition vehicles and alternative fuel compression-ignition vehicles. CO2 emissions test group result (grams per mile)/10,180 grams per gallon of diesel fuel) × (10 2) = Fuel consumption test group result (gallons per 100 mile).

(ii) Calculate the equivalent fuel consumption test group results as follows for spark-ignition vehicles and alternative fuel spark-ignition vehicles. CO2 emissions test group result (grams per mile)/((8,887 grams per gallon of gasoline fuel) × (10−2)) = Fuel consumption test group result (gallons per 100 mile).

(5) Calculate the fleet average fuel consumption result, in gallons per 100 miles, from the equivalent fuel consumption test group results and round the fuel consumption result to the nearest 0.001 gallon per 100 miles. Calculate the fleet average fuel consumption result using the following equation.

$\text{Fleet Average Fuel Consumption}=\frac{\sum \left[{\text{Fuel Consumption Test Group Result}}_{i}×{\mathrm{Volume}}_{i}\right]}{\sum \left[{\mathrm{Volume}}_{i}\right]}$
Where:
Fuel Consumption Test Group Resulti = fuel consumption performance for each test group as defined in 49 CFR 523.4.
Volumei = production volume of each test group.

(6) Compare the fleet average fuel consumption standard to the fleet average fuel consumption performance. The fleet average fuel consumption performance must be less than or equal to the fleet fuel consumption standard to comply with standards in § 535.5(a).

(b) Heavy-duty vocational vehicles and tractors. This section describes the method for determining the fuel consumption performance rates for vehicle families of heavy-duty vocational vehicles and tractors. The NHTSA heavy-duty vocational vehicle and tractor fuel consumption performance rates correspond to the same requirements for EPA as specified in 40 CFR 1037, subpart F.

(1) Select vehicles and vehicle family configurations to test as specified in 40 CFR 1037.230 for vehicles that make up each of the manufacturer's regulatory subcategories of vocational vehicles and tractors. For the Phase 2 program, select powertrain, axle and transmission families in accordance with 40 CFR 1037.231 and 1037.232.

(2) Follow the EPA testing requirements in 40 CFR 1037.230 and 1037.501 to derive inputs for the Greenhouse gas Emissions Model (GEM).

(3) Enter inputs into GEM, in accordance with 40 CFR 1037.520, to derive the emissions and fuel consumption performance results for all vehicles (conventional, alternative fueled and advanced technology vehicles).

(4) For Phase 1 and 2, all of the following GEM inputs apply for vocational vehicles and other tractor regulatory subcategories, as follows:

(i) Model year and regulatory subcategory (see § 535.3 and 40 CFR 1037.230).

(ii) Coefficient of aerodynamic drag or drag area, as described in 40 CFR 1037.520(b) (tractors only for Phase 1).

(iii) Steer and drive tire rolling resistance, as described in 40 CFR 1037.520(c).

(iv) Vehicle speed limit, as described in 40 CFR 1037.520(d) (tractors only).

(v) Vehicle weight reduction, as described in 40 CFR 1037.520(e) (tractors only for Phase 1).

(vi) Automatic engine shutdown systems, as described in 40 CFR 1037.660 (only for Phase 1 Class 8 sleeper cabs). For Phase 1, enter a GEM input value of 5.0 g/ton-mile, or an adjusted value as specified in 40 CFR 1037.660.

(5) For Phase 2 vehicles, the GEM inputs described in paragraphs (b)(4)(i) through (v) of this section continue to apply. Note that the provisions related to vehicle speed limiters and automatic engine shutdown systems are available for vocational vehicles in Phase 2. The additional GEM inputs that apply for vocational vehicles and other tractor regulatory subcategories for demonstrating compliance with Phase 2 standards are as follows:

(i) Engine characteristics. Enter information from the engine manufacturer to describe the installed engine and its operating parameters as described in 40 CFR 1036.510 and 1037.520(f).

(ii) Vehicle information. Enter information in accordance with 40 CFR 1037.520(g) for the vehicle and its operating parameters including:

(A) Transmission make, model and type;

(B) Drive axle configuration;

(C) Drive axle ratio, ka;

(D) GEM inputs associated with powertrain testing include powertrain family, transmission calibration identifier, test data from 40 CFR 1037.550, and the powertrain test configuration (dynamometer connected to transmission output or wheel hub).

(iii) Idle-reduction technologies. Identify whether the manufacturer's vehicle has qualifying idle-reduction technologies, subject to the qualifying criteria in 40 and 1037.660 and enter values for stop start and neutral idle technologies as specified in 40 CFR 1037.520(h).

(iv) Axle and transmission efficiency. Manufacturers may use axle efficiency maps as described in 40 CFR 1037.560 and transmission efficiency maps as described in 40 CFR 1037.565 to replace the default values in GEM.

(v) Additional reduction technologies. Enter input values in GEM as follows to characterize the percentage CO2 emission reduction corresponding to certain technologies and vehicle configurations, or enter 0 as specified in 40 CFR 1037.520(j):

(A) Intelligent controls

(C) Tire-pressure systems

(D) Extended-idle reduction

(E) Additional GEM inputs may apply as follows:

(1) Enter 1.7 and 0.9, respectively, for school buses and coach buses that have at least seven available forward gears.

(2) If the agencies approve an off-cycle technology under § 535.7(f) and 40 CFR 1037.610 in the form of an improvement factor, enter the improvement factor expressed as a percentage reduction in CO2 emissions. (Note: In the case of approved off-cycle technologies whose benefit is quantified as a g/ton-mile credit, apply the credit to the GEM result, not as a GEM input value.)

(vi) Vehicles with hybrid power take-off (PTO). For vocational vehicles, determine the delta PTO emission result of the manufacturer's engine and hybrid power take-off system as described in 40 CFR 1037.540.

(vii) Aerodynamic improvements for vocational vehicles. For vocational vehicles certified using the Regional duty cycle, enter ΔCdA values to account for using rear fairings and a reduced minimum frontal area as specified in 40 CFR 1037.520(m) and 1037.527.

(viii) Alternate fuels. For fuels other than those identified in GEM, perform the simulation by identifying the vehicle as being diesel-fueled if the engine is subject to the compression-ignition standard, or as being gasoline-fueled if the engine is subject to the spark-ignition standards. Correct the engine or powertrain fuel map for mass-specific net energy content as described in 40 CFR 1036.535(b).

(ix) Custom chassis vehicles. A simplified versions of GEM applies for custom chassis vehicle subject § 535.5(b)(6) in accordance with 40 CFR 1037.520(a)(2)(ii).

(6) In unusual circumstances, manufacturers may ask EPA to use weighted average results of multiple GEM runs to represent special technologies for which no single GEM run can accurately reflect.

(7) From the GEM results, select the CO2 family emissions level (FEL) and equivalent fuel consumption values for vocational vehicle and tractor families in each regulatory subcategory for each model year. Equivalent fuel consumption FELs are derived in GEM and expressed to the nearest 0.0001 gallons per 1000 ton-mile. For families containing multiple subfamilies, identify the FELs for each subfamily.

(c) [Reserved]

(d) Heavy-duty engines. This section describes the method for determining equivalent fuel consumption family certification level (FCL) values for engine families of heavy-duty truck tractors and vocational vehicles. The NHTSA heavy-duty engine fuel consumption FCLs are determined from the EPA FCLs tested in accordance with 40 CFR 1036, subpart F. Each engine family must use the same primary intended service class as designated for EPA in accordance with 40 CFR 1036.140.

(1) Manufacturers must select emission-data engines representing the tested configuration of each engine family specified in 40 CFR part 86 and 40 CFR 1036.235 for engines in heavy-duty truck tractors and vocational vehicles that make up each of the manufacture's regulatory subcategories.

(2) Standards in § 535.5(d) apply to the CO2 emissions rates for each emissions-data engine in an engine family subject to the procedures and equipment specified in 40 CFR part 1036, subpart F. Determine equivalent fuel consumptions rates using CO2 emissions rates in grams per hp-hr measured to at least one more decimal place than that of the applicable EPA standard in 40 CFR 1036.108.

(i) Use the CO2 emissions test results for engines running on each fuel type for conventional, dedicated, multi-fueled (dual-fuel, and flexible-fuel) engines as specified in 40 CFR part 1036, subpart F.

(ii) Use the CO2 emissions result for multi-fueled engines using the same weighted fuel mixture emission results as specified in 40 CFR 1036.235 and 40 CFR part 1036, subpart F.

(iii) Use the CO2 emissions test results for hybrid engines as described in 40 CFR 1036.525.

(iv) All electric vehicles are deemed to have zero emissions of CO2 and zero fuel consumption. No emission or fuel consumption testing is required for such electric vehicles.

(3) Use the CO2 emissions test results for tractor engine families in accordance with 40 CFR 1036.501 and for vocational vehicle engine families in accordance with 40 CFR part 86, subpart N, for each heavy-duty engine regulatory subcategory for each model year.

(i) If a manufacturer certifies an engine family for use both as a vocational engine and as a tractor engine, the manufacturer must split the family into two separate subfamilies in accordance with 40 CFR 1036.230. The manufacturer may assign the numbers and configurations of engines within the respective subfamilies at any time prior to the submission of the end-of-year report required by 40 CFR 1036.730 and § 535.8. The manufacturer must track into which type of vehicle each engine is installed, although EPA may allow the manufacturer to use statistical methods to determine this for a fraction of its engines.

(ii) The following engines are excluded from the engine families used to determine fuel consumption FCL values and the benefit for these engines is determined as an advanced technology credit under the ABT provisions provided in § 535.7(e); these provisions apply only for the Phase 1 program:

(A) Engines certified as hybrid engines or power packs.

(B) Engines certified as hybrid engines designed with PTO capability and that are sold with the engine coupled to a transmission.

(C) Engines with Rankine cycle waste heat recovery.

(4) Manufacturers generating CO2 emissions rates to demonstrate compliance to EPA vehicle standards for model years 2021 and later, using engine fuel maps determined in accordance with 40 CFR 1036.535 and 1036.540 or engine powertrain results configuration, must use the same compliance pathway and model years for certifying under the NHTSA program. Manufacturers may omit providing equivalent fuel consumption FCLs under this section if all of its engines will be installed in vehicles that are certified based on powertrain testing as described in 40 CFR 1037.550.

(5) Calculate equivalent fuel consumption values from the emissions CO2 FCLs levels for certified engines, in gallons per 100 hp-hr and round each fuel consumption value to the nearest 0.0001 gallon per 100 hp-hr.

(i) Calculate equivalent fuel consumption FCL values for compression-ignition engines and alternative fuel compression-ignition engines. CO2 FCL value (grams per hp-hr)/10,180 grams per gallon of diesel fuel) × (10 2) = Fuel consumption FCL value (gallons per 100 hp-hr).

(ii) Calculate equivalent fuel consumption FCL values for spark-ignition engines and alternative fuel spark-ignition engines. CO2 FCL value (grams per hp-hr)/((8,887 grams per gallon of gasoline fuel) × (10−2)) = Fuel consumption FCL value (gallons per 100 hp-hr).

(iii) Manufacturers may carryover fuel consumption data from a previous model year if allowed to carry over emissions data for EPA in accordance with 40 CFR 1036.235.

(iv) If a manufacturer uses an alternate test procedure under 40 CFR 1065.10 and subsequently the data is rejected by EPA, NHTSA will also reject the data.

(e) Heavy-duty trailers. This section describes the method for determining the fuel consumption performance rates for trailers. The NHTSA heavy-duty trailers fuel consumption performance rates correspond to the same requirements for EPA as specified in 40 CFR part 1037, subpart F.

(1) Select trailer family configurations that make up each of the manufacturer's regulatory subcategories of heavy-duty trailers in 40 CFR 1037.230 and § 535.4.

(2) Obtain preliminary approvals for trailer aerodynamic devices from EPA in accordance with 40 CFR 1037.150.

(3) For manufacturers voluntarily complying in model years 2018 through 2020, and for trailers complying with mandatory standards in model years 2021 and later, determine the CO2 emissions and fuel consumption results for partial- and full-aero trailers using the equations and technologies specified in 40 CFR part 1037, subpart F. Use testing to determine input values in accordance with 40 CFR 1037.515.

(4) From the equation results, use the CO2 family emissions level (FEL) to calculate equivalent fuel consumption FELs are expressed to the nearest 0.0001 gallons per 1000 ton-mile.

(i) For families containing multiple subfamilies, identify the FELs for each subfamily.

(ii) Calculate equivalent fuel consumption FEL values for trailer families. CO2 FEL value (grams per 1000 ton-mile)/10,180 grams per 1000 ton-mile of diesel fuel) × (10 3) = Fuel consumption FEL value. The equivalent fuel consumption FELs are expressed to the nearest 0.0001 gallons per 1000 ton-mile.

[81 FR 74238, Oct. 25, 2016, as amended at 85 FR 25274, Apr. 30, 2020]