40 CFR § 1037.515  Determining CO2 emissions to show compliance for trailers.
This section describes a compliance approach for trailers that is consistent with the modeling for vocational vehicles and tractors described in § 1037.520, but is simplified consistent with the smaller number of trailer parameters that affect CO2 emissions. Note that the calculated CO2 emission rate, eCO2, is equivalent to the value that would result from running GEM with the same input values.
(a) Compliance equation. Calculate CO2 emissions for demonstrating compliance with emission standards for each trailer configuration.
(1) Use the following equation:
Table 1 of § 1037.515  Regression Coefficients for Calculating CO2 Emissions
Trailer category 





Long dry box van  76.1  1.67  −5.82  −0.00103 
Long refrigerated box van  77.4  1.75  −5.78  −0.00103 
Short dry box van  117.8  1.78  −9.48  −0.00258 
Short refrigerated box van  121.1  1.88  −9.36  −0.00264 
(2) The following is an example for calculating the mass of CO2 emissions, eCO2, from a long dry box van that has a tire pressure monitoring system for all wheels, an aluminum suspension assembly, aluminum floor, and is designated as Bin IV:
(b) Tire rolling resistance. Use the procedure specified in § 1037.520(c) to determine the tire rolling resistance level for your tires. Note that you may base tire rolling resistance levels on measurements performed by tire manufacturers, as long as those measurements meet this part's specifications.
(c) Drag area. You may use ΔCdA values approved under § 1037.211 for device manufacturers if your trailers are properly equipped with those devices. Determine ΔCdA values for other trailers based on testing. Measure CdA and determine ΔCdA values as described in § 1037.526(a). You may use ΔCdA values from one trailer configuration to represent any number of additional trailers based on worstcase testing. This means that you may apply ΔCdA values from your measurements to any trailer models of the same category with drag area at or below that of the tested configuration. For trailers in the short dry box vans and short refrigerated box vans that are not 28 feet long, apply the ΔCdA value established for a comparable 28foot trailer model; you may use the same devices designed for 28foot trailers or you may adapt those devices as appropriate for the different trailer length, consistent with good engineering judgment. For example, 48foot trailers may use longer side skirts than the skirts that were tested with a 28foot trailer. Trailer and device manufacturers may seek preliminary approval for these adaptations. Determine bin levels based on ΔCdA test results as described in the following table:
Table 2 of § 1037.515  Bin Determinations for Trailers Based on Aerodynamic Test Results
[ΔCdA in m2]
If a trailer's measured Δ 
Designate the trailer as . . .  And use the following value for Δ 

≤0.09  Bin I  0.0 
0.100.39  Bin II  0.1 
0.400.69  Bin III  0.4 
0.700.99  Bin IV  0.7 
1.001.39  Bin V  1.0 
1.401.79  Bin VI  1.4 
≥1.80  Bin VII  1.8 
(d) Weight reduction. Determine weight reduction for a trailer configuration by summing all applicable values, as follows:
(1) Determine weight reduction for using lightweight materials for wheels as described in § 1037.520(e).
(2) Apply weight reductions for other components made with lightweight materials as shown in the following table:
Table 3 of § 1037.515  Weight Reductions for Trailers
[pounds]
Component  Material  Weight
reduction (pounds) 

Structure for Suspension Assembly 
Aluminum  280 
Hub and Drum (per axle)  Aluminum  80 
Floor 
Aluminum  375 
Floor 
Composite (wood and plastic)  245 
Floor Crossmembers 
Aluminum  250 
Landing Gear  Aluminum  50 
Rear Door  Aluminum  187 
Rear Door Surround  Aluminum  150 
Roof Bows  Aluminum  100 
Side Posts  Aluminum  300 
Slider Box  Aluminum  150 
Upper Coupler Assembly  Aluminum  430 
a For tandemaxle suspension subframes made of aluminum, apply a weight reduction of 280 pounds. Use good engineering judgment to estimate a weight reduction for using aluminum subframes with other axle configurations.
b Calculate a smaller weight reduction for short trailers by multiplying the indicated values by 0.528 (28/53).
(e) Offcycle. You may apply the offcycle provisions of § 1037.610 to trailers as follows:
(1) You may account for weight reduction based on measured values instead of using paragraph (d) of this section. Quantify the weight reduction by measuring the weight of a trailer in a certified configuration and comparing it to the weight of an equivalent trailer without weightreduction technologies. This qualifies as A to B testing under § 1037.610. Use good engineering judgment to select an equivalent trailer representing a baseline configuration. Use the calculated weight reduction in Eq. 1037.5151 to calculate the trailer's CO2 emission rate.
(2) If your offcycle technology reduces emissions in a way that is proportional to measured emissions as described in § 1037.610(b)(1), multiply the trailer's CO2 emission rate by the appropriate improvement factor.
(3) If your offcycle technology does not yield emission reductions that are proportional to measured emissions, as described in § 1037.610(b)(2), calculate an adjusted CO2 emission rate for your trailers by subtracting the appropriate offcycle credit.
(4) Note that these offcycle provisions do not apply for trailers subject to design standards.