### UNITED STA **TES ENVIRONMENTA L PROTECTION A** **GENCY** NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2565 PLYMOUTH ROAD ANN ARBOR, MI 48105 - 2498
OFFICE OF AIR AND RADIATION 

### July 8 , 2015 MEMORANDUM SUBJECT: Numerical Standards for Tractors, Trailers, and Vocational Vehicles Based on the GEM

Executable Code ; and Derivation of the Numerical Engine Standards FROM: Angela Cullen, Engineer, Assessment and Standards Division

Jessica Brakora, Engineer, Assessment and Standards Division Lauren Steele, Engineer, Assessment and Standards Division TO: Greenhous e Gas Emissions Standards and Fuel Efficiency Standards for Medium
- and Heavy- Duty

Engines and Vehicles
- Phase 2
- Docket EPA - HQ - OAR- 201 4 - 0827 **Numerical Standards for Tractors, Trailers, and Vocational Vehicles**  The agencies established the proposed standards by evaluating specific vehicle technology packages using a prepublication version of the Phase 2 GEM. This prepublication version was an intermediate version of the GEM source code, rather than the executable file version of GEM, which is being docketed for this proposal and is available on EPA’s GEM Webpage. Both the GEM source code and the GEM executable file are generally functionally

equivalent. Formal external peer review and expert external user review was then conducted on the version of the GEM source code that was used to calculate the numerical values of the proposed standards. It was discovered via these external review processes that the GEM source code contained some minor software “bugs
. ” These bugs were then corrected by EPA and the Phase 2 proposed GEM executable file was derived from this corrected version of the GEM source code. Moreover, we expect to also receive technical comments during the comment period that could potentially identify additional GEM software bugs, which would lead EPA to make additional changes to GEM before the Final Rule. Thus, even without the agencies making any changes in our projections of technology effectiveness or market adoption rates, it is likely that further revisions to GEM could result in us finalizing different numerical values for the standards. It is important to note that the agencies would not necessarily consider such GEM
-based numerical changes by themselves to be changes in the stringency

of the standards. Rather, we believe that stringency is more appropriately evaluated in technological terms; namely, by evaluating technology

effectiveness and the market adoption rates of technologies. The tables below compare results from the prepublication GEM source code with results from the proposed GEM executable for combination tractors, vocational vehicles, and trailers. The comb ination tractor results are directly from each version of GEM. The vocational vehicle GEM results

### 2

underwent post
-processing to recognize idle reduction technolo gi es as well as to make some adjustments as described below. The trailer results are based on equations developed from both the prepublication and proposed GEM versions. Note that NHTSA fuel consumption values are not shown in the tables below. These values have been calculated using a conversion factor of 10,180 grams CO 2 

### per gallon of diesel fuel , or 8,887 grams CO 2 

### per gallon of gasoline , and are presented in the supporting documentation for GEM
. Itshould also be noted that the version of the GEM ex ecutable code that was used for developing the stringencies use s unrounded inputs, which is different than the compliance version of the GEM executable, which will round the inputs. **Table 1**  **: Com** **parison of GEM R esults for Combinati** **on Tractors**

**Class 7 Class 8**  **Heavy Haul**  **Day Cab Day Cab**  **Sleeper Cab Low**  **Roof Mid**  **Roof High**  **Roof Low**  **Roof Mid**  **Roof High**  **Roof Low**  **Roof Mid**  **Roof High**  **Roof Baseline**  Pre -Publication Source Code 107 118 121 86 93 95 79 87 88 57 Propos ed GEM Exe cutable 106 117 120 85 92 94 79 87 88 57 **2021** Pre -Publication Source Code 97 107 109 78 84 86 70 78 77 54 Proposed GEM Exe cutable 96 107 109 77 84 86 70 78 77 54 **2024** Pre -Publication Source Code 90 100 101 72 78 79 64 71 70 52 Proposed GEM Exe cutable 89 99 100 72 7 8 78 6 4 7 1 7 0 51 **2027** Pre -Publication Source Code 87 96 96 70 76 76 62 69 67 51 Proposed GEM Exe cutable 86 96 96 70 76 76 62 69 67 51

**Table 2**  **: Com parison of Coefficients for GEM**  **- Based Trailer Com** **pliance Equations Subcategory**  **GEM Version**  **GEM -**  **Based Equation Constants Intercept**  **Aero CRR**  **WR** Long Dry Van Pre -Publication Source Code 77.4 - 6.1 1.7 - 0.001 Proposed GEM Executable 77.1 - 6.1 1.7 - 0.0011 Long Refrigerated Van Pre -Publication Source Code 78.3 - 6.0 1.8 - 0.001 Proposed GEM Executable 78.0 - 6.0 1.8 - 0.0011 Short Dry Van Pre -Publication Source Code 134.0 - 10.5 2.2 - 0.003 Proposed GEM Executable 133.4 - 10.2 2.2 - 0.0031 Short Refrigerated Van Pre -Publication Source Code 136.3 - 10.3 2.4 - 0.003 Proposed GEM Executable 136 - 10.1 2.4 - 0.0031 **Table 3**  **: Com parison of GEM**  **- Based Equation Results for Trailers**  **Dry Van Refrigerated Van**  **Long Short**  **Long Short**  **Baseline** Pre -Publication Source Code 85 147 86 151 Proposed GEM Exe cutable 84 147 86 150 **2018** Pre -Publication Source Code 83 144 84 147 Proposed GEM Exe cutable 82 143 84 147

### 3 **Dry Van Refrigerated Van**  **Long Short**  **Long Short**  **2021** Pre -Publication Source Code 81 142 82 146 Proposed GEM Exe cutable 81 142 82 1 45 **2024** Pre -Publication Source Code 79 141 81 144 Proposed GEM Exe cutable 79 140 80 144 **2027** Pre -Publication Source Code 77 140 80 144 Proposed GEM Exe cutable 77 139 79 143 **Table 4**  **: Com parison of Post** **- Processed GEM**  **Results for Vocational Vehicles** 

### LHD **MHD HHD**  Pre -Publication Source Code Proposed GEM

Executable Pre -Publication

Source Code Proposed GEM

Executable Pre -Publication

Source Code Proposed GEM

Executable **CI Baseline** U a 316 31 5 201 20 0 212 224 M 325 32 4 203 203 214 228 R 339 33 8 199 19 9 203 221 E 318 31 7 200 200 223 236 **SI Baseline** U 334 33 3 213 21 2 224 237 M 344 34 3 215 215 226 241 R 358 35 8 211 2 10 214 234 **CI 2021** U 296 295 188 187 198 20 9 M 305 304 190 189 200 21 3 R 318 31 7 186 18 6 189 20 7 E 312 311 195 196 215 231 **SI 2021** U 320 31 9 203 202 214 22 6 M 329 32 9 205 20 5 216 2 30 R 343 342 201 20 1 204 22 3 **CI 2024** U 284 282 179 17 9 190 19 9 M 292 29 1 181 18 1 192 20 3 R 304 303 178 177 182 19 7 **SI 2024** U 312 310 197 19 7 208 21 9 M 321 3 20 199 19 9 210 22 3 R 334 333 196 195 199 21 7

### 4 **LHD MHD**  **HHD** Pre -Publication Source Code Proposed GEM

Executable Pre -Publication

Source Code Proposed GEM

Executable Pre -Publication

Source Code Proposed GEM

Executable **CI 2027** U 272 265 172 16 8 182 18 8 M 280 273 174 1 70 183 19 2 R 292 28 5 170 166 174 18 6 **SI 2027** U 299 29 2 189 18 5 196 20 7 M 308 30 1 191 18 7 198 2 11 R 321 31 4 187 183 188 20 5 Note: a U = Urban, M = Multipurpose, R = Regional, E = Emergency 

### Derivation **of Vocational Vehicle**  **Standard s**  The agencies developed a method to normalize the standards so that vehicles certified over the Regional composite cycle would have similar stringency as vehicles certified over the Multi
- Purpose or Urban cycles. The reason for this is that the agencies expect each vehicle to be tested with an a ppropriate duty cycle for its intended application and want to minimize unintended incentives to place a vehicle in a less appropriate subcategory to receive a benefit of a less stringent standard
. A summary of the normalizing process can be found in the draft RIA Chapter 2.9.2.1. Characteristics of the baseline vehicles that were used for each sub category can be found in the draft RIA: Predefined modeling parameters are presented in Table 4
- 8, 4 - 9 and 4
- 10 of the draft RIA Chapter 4; and User
- enterable modeling parameters are presented in Table 2
- 43, 2 - 44, and 2
- 45 of draft RIA Chapter 2.9.2. As described in draft RIA Chapter 2 .9.2.1, the agencies identified a “best baseline vehicle” with which to normalize the performance of the defined baseline vehicles of the three duty c ycl es within each weight class. Table 5 lists some characteristics of the vehicles that the agencies chos e as the “best baseline vehicles” for each weight class. For the HHD weight class, these are the vehicles intended to be certified over the Regional cycle, while for the MHD and LHD weight classes, these are the vehicles intended to be certified over the Multi
- Purpose cycles. In the draft RIA at 2.9.2.1, it is stated that the best vehicle for LHD and MHD was the Urban vehicle, however that statement was an error. In the LHD weight class, the Multi
- Purpose vehicle is identical to the Urban vehicle, and in the MHD weight class, the Multi
- Purpose vehicle is nearly identical to the Urban vehicle, with a slightly different tire radius.

### 5 **Table 5**  **: Best Vocational**  **Baseline Vehicles** 

### Weight Category Engine Transmission Tire Radius (m) Drive Axle

R atio Steer CRR

(kg/t) Drive CRR

(kg/t) HH D 455 hp 10 spd MT 0.483 3.76 7.7 7.7 MH D 270 hp 5 spd MH AT 0.462 4.88 7.7 7.7 LH D 200 hp 5 spd MH AT 0.378 4.56 7.7 7.7 GEM was used to simulate each of the vehicles over its intended duty cycle as well as over the other two composite cycles
. Following the process described in the draft RIA 2.9.2.1, the normalization process using the proposed GEM executable yi elds values presented in Table 6 , which can be compared with the results obtained using the pre -publication source code, as presented in Table 2
- 46 of the draft RIA. **Table 6**  **: Vocational Baseline Norm alizing** 

CLASS 2 b - 5 CLASS 6 - 7 CLASS 8 Urban Multi Purpose Regional Urban Multi Purpose Regional Urban Multi Purpose Regional **Straight GEM Baseline Performance** 31 7 32 7 331 200 204 19 7 236 233 200 **Normalization Factor** 0.97 1.0 0 1.0 4 1.00 1.0 1 0.99 0.99 1.0 1 0.9 8 **Population Weighted Best Vehicle**  **Result** 32 8.8 202.4 193.9

**Population Weighted Baseline Result**  3 2 5.5 201. 1 2 25.3 **Normalized Baseline** 31 5 32 4 3 3 8 20 0 20 3 19 9 2 24 2 28 2 21 

### The numerical stringencies of the proposed standards were determined b y applying technology effectiveness and adoption rates as described in the proposal (see draft RIA 2.9.5) , then averaging the subcategory
- specific percent improvements within each weight class, then calculating the numerical value of the standard b y applying this averaged percent improvement to the normalized baseline. For example, for MY 2027 in the HHD weight class, the technology package as specified in the proposal for the Regional subcategory would achieve 1 1 . 6 % improvement, the Multi
-purpose technology package would achieve 17.4% improvement, and the Urban technology package would achieve 18.9% improvement. These average to 16%, so the HHD 2027 standards were calculated by reducing each of the HHD normalized baseline values b y 16%. **Derivation of the Proposed Engine Standards** As described in Section II.D(a) of the HD Phase 2 Notice of Proposed Rulemaking, the agencies derived the proposed engine standards based on our projections of the effectiveness of various technologies over the proposed engine test cycles (i.e., percent reduction) and the extent to which such technologies could be adopted by industry by 2021, 2024, and 2027. The values used for tractor engines are shown in Table 7 b elow.

### 6 **Table 7**  **: Projected Tractor Engine Technologies and Reduction**  **SET -** **WEIGHTED REDUCTION (%)**  **2020 -** **2027 MARKET** 

**PENETRATION (2021)**  **MARKET**

**PENETRATION (2024)**  **MARKET**

**PENETRATION (2027)**  Turbo compound with clutch 1.8% 5% 10% 10% WH R (Rankine cycle) 3.6% 1% 5% 15% Parasitic/Friction (Cyl Kits, pumps, FIE), lubrication 1.4% 45% 95% 100% Aftertreatment (lower dP) 0.6% 45% 95% 100% EGR/Intake & exhaust manifolds/Turbo /VVT/Ports 1.1% 45% 95% 100% Combustion/FI/Control 1.1% 45% 95% 100% Downsizing 0.3% 10% 20% 30% Dis - Synergy Factor 75% 85% 85% We ighted Reduction for Engines w/o TC or W HR 1.45% 3.44% 3.64 We ighted Reduction for Engines with TC 2.79% 4.92% 5.12 % We ighted Reduction for Engines with W HR 4.08% 6.36 % 6.56% **Total Weighted**  **R eduction (%** **) 1.5%**  **3.7% 4.2%**  

### The proposed standards were derived from the weighted reductions which combined all these technologies by

multiplying together an effectiveness factor for each technology (equal to 100% minus the SET weighted percent reduction times the market penetration) and applyinga dis
- sy nergy factor that reflects the degree to which combining multiple technologies reduces slightly the effectiveness of each individual technology
. The assumed dis
- sy nergy factors are also shown in Table 7. Because turbo compound and Rankine cycle waste heat recovery are mutually exclusive technologies, we calculated intermediate values for engines without either turbo compound or Rankine cycle waste heat recovery, and for engines with either turbo compound or Rankine cycle waste heat recovery
. These intermediate values are also shown in Table 7. For example, the average percent reduction in 2021 for engines without either turbo compound or Rankine cycle waste heat recovery would be: [100% - ( 100% - (45% ×1.4%))×(100%
- (45% ×0.6%))×(100%
- (45% ×1.1%))×(100%
- (10% ×0.3%))]×75% = 1.45% 

### For each change in the standards (in 2021, 2024, and 2027) these intermediate values were combined based on the projected penetrations for turbo compound or Rankine cycle waste heat recovery . For example, the total weighted reduction for 2021 was calculated as: 1.45% × (100%
- 5 % - 1 %) + 2.79 % × 5 % + 4.08 % × 1% = 1. 5 4 3 % 

### This same approach was used to calculate the proposed vocational engine standards , although it was not necessary

to calculate intermediate values
. Table 8 below summarizes the derivation of the vocational engine standards.

### 7 **Table 8 :**  **Projected Vocational Engine Technologies and Reduction**  **FTP WEIGHTED REDUCTION (%)**  **2021 -** **2027 MARKET** 

**PENETRATION 2021**  **MARKET**

**PENETRATION 2024**  **MARKET**

**PENETRATION 2027**  Model based control 2.0% 25% 30% 40% Parasitic /Friction 1.5% 60% 90% 100% EGR/Air/VVT /Turbo 1.0% 50% 90% 100% Improved AT 0.5% 50% 90% 100% Combustion Optimization 1.0% 50% 90% 100% Dis - Synergy Factor 75% 85% 85% **Total Weighted**  **reduction (% )**  **2.0% 3.5%**  **4.0%** 

### The numerical tractor and vocational engine standards for Alternatives 2, 4, and 5 were also calculated in the same manner as the proposed engine standards.