### 1 MEMORANDUM
TO: Docket EPA-HQ-OAR-2011-0135

FROM: James Warila, Assessment and Standards Division, Office of Transportation and Air Quality



### DATE: December 2011

RE: Developing Emission Rates Representing the Effect of Proposed Tier-3 Standards on Gaseous Emissions from Gasoline-P owered Light-duty Vehi cles (HC/CO/NOx)

Gaseous emission rates in MOVES are stored in a database table (EmissionRateByAge) that expresses emission rates as mass per time, distin guished by emission process (start and running), fuel type (gas and diesel), vehicle regulatory class (LDV, LDT, Light HD, etc.), model year, age, and operating mode (power/speed for runnin g, vehicle soak time for start). Developing rates to reflect Tier 3 controls required acc ounting for expected changes in each of these dimensions.
Developing rates to represent emissions for Tier-3 vehicles follows same procedures used to develop rates used in the default database, as described in the documentation for development of light-duty exhaust emission rates for MOVES2010 i 

### . However, specific modifications were made to represent the introduction of Tier-3 standards, as described below. Where no modifications to methods were made, we will refe r the reader to the appr opriate section of the MOVES2010 report. In partic ular, see Section 1.3.4.
The process involves six steps, list ed below. As described in the report, the first four steps in this process are applied to calculate the meanBaseRateIM 1 

### for the 0-3 year ageGroup (with deterioration to be applied in Step 5). The ra tes are estimated by Tier, model year and regulatory class. 1. Average FTP results by standard level and vehicle class. As in the default database, we made use of data measured on the FTP cycle in the course of the In-u se Verification Program (IUVP).

2. Develop phase-in assumptions for MY 2017 – 2031, by standard level, vehicle class and model year.

3. Merge FTP results and Phase-in assumptions . For running emissions, calculate weighted ratios of emissions in each model year rela tive to those for cars (LDV) in MY2000, which represent Tier-1 LDV.

1 The field “meanBaseRateIM” in the emissionRateByAge table represents m ean rates for vehicles subject to requirements of the Phoenix Inspection-a nd-Maintenance Program. In the technical report, this field is referred to as the “I/M Reference rate.” However, this use of the term should not be confused with the “Reference Case” in the Rulemaking.

### 2 4. Estimate Emissions by Operating Mode . Then calculate emissions by operating mode in each model year by multiplying the MY2000 emission rates by the weighted ratio for each model year. We assume that the emissions contro l at high power (outside ranges of speed and acceleration covered by Bag 2 of th e FTP) would not be as effec tive as at lower power (within the range of speed and accel eration covered by Bag 2).

5. Apply Deterioration to estimate emissions for three a dditional age Groups (4-5, 6-7 and 8- 9). We assume that NLEV and Tier -2 vehicles will deteriorate similarly to Tier-1 vehicles, when viewed in logarithmic terms. We therefore apply ln-linear deterior ation to the rates developed in steps 1-4. For the remaining three age groups, emi ssions are assumed to stabilize as described in the MOVES2010 report.
6. Estimate non-I/M reference rates . The rates in steps 1-6 represent I/M references. Corresponding non-I/M references are calculated by a pplying the ratios applie d to the Tier-1 and pre-Tier-1 rates.
We followed these steps, with specific modificati ons to represent Tier 3 rates. In step 1, we developed estimates of FTP results under Tier 3, including composite results, “cold-start” emissions” (Bag1-Bag3) and “hot-running” emissi ons (Bag 2 FTP and US06). For step 2, we developed phase-in assumptions re presenting the introduction of Tie r-3 standards. In Step 5 we modified deterioration to repres ent a useful life of 150,000 miles, as opposed to the useful life of 120K mi, assumed for Tier-2 and NLEV vehicles . Each of these steps and modifications is described in greater detail in the sub-sections below.

1.1 Averaging FTP Results (Step 1) (Standard)
Modeling to project emissions for Tier-3 vehicles is driven by the NMOG+NO x 

### standard, set at 30 mg/mi. However, because MOVES proj ects NOx and THC emissions separately, we apportioned the aggregate standard into NMOG and NO x 

### components, which we will refer to as the “effective standards” for each pollutant. Fo r purposes of apportionment, we assumed that NMOG control would pose a greate r technical challenge than NO x 

### control. Accordingly, we assumed “effective standards” for NMOG and NO x of 20 mg/mi and 10 mg/mi, respectively. To implement this assumption, we further assumed that for NO x 

### , vehicles would be effectively brought into Bin 2, and that for NMOG, vehicles would be brought to a level between Bin 2 and Bin 3, but closer to Bin 2.
In addition, MOVES models start and running processes separately. It is therefore necessary to translate the composite standard into start and running components. One component represents a “cold start” on the FTP cycle, re presented as “Bag1 – Bag3” emissions. A second component represents “hot-running” emissions, represented by the hot-ru nning phase of the FTP (Bag 2). A third component represents emissions on the US06 cycle, repr esenting emissions at high speed and power.

Estimated FTP and US06 emissions levels for hydrocarbons (NMOG and NMHC) are shown in Table 1, for several Tier-2 Bins and for Tier 3. Values for all standards except Tier 3 are

### 3 identical to those used to develop rates in th e default database. The values for Tier 3 are calculated as a weighted average of t hose for Bins 2 and 3, using Equation 1.



### 3 B 225

. 0 2 B 775

. 0 3 T

    Equation 1



### Table 1. Hydrocarbons (HC): Useful-Life FT P Standards and Associated Cold-Start and Hot-Running Results on the FTP and US06 Cycl es. Values for the FTP and US06 represent NMOG and NMHC, respectively.

Bin Useful-life Standard (mg/mi) FTP Composite 1 (mg/mi) FTP Cold Start 1 (mg) FTP hot Running 1 (Bag 2) (mg/mi) US06 2 (mg/mi)

8 125 41.3 591 3.56 35.8 5 90 35.5 534 2.63 35.8 4 70 24.8 383 2.28 35.8 3 55 21.5 329 1.74 35.8 2 10 5.6 87 0.42 2.60

Tier 3 3 20 9.2 142 0.7 10.0 1 Values represent “non-methane organic gases” (NMOG). 2 Values represent “non-methane hydrocarbons” (NMHC). 3 Values for Tier 3 calculated using Equation 1.



### Under a general assumption that CO standards ar e not forcing, but that CO emissions tend to track NMOG emissions, corresponding values for CO were calculated in the same manner, and are presented in Table 2.

Table 2. CO: Useful-Life FTP Standards a nd Associated Cold-Start and Hot-Running Results on the FTP and US06 Cycles.

Bin Useful-lifeStandard (mg/mi) FTP Composite (mg/mi) Cold Start (mg) FTP hot Running (Bag 2) (mg/mi) US06 (mg/mi)

8 4,200 861 6,680 451 2,895 5 4,200 606 5,510 238 2,895 4 4,200 537 5,500 201 2,895 3 2,100 463 3,470 119 2,895 2 2,100 235 1,620 70 948

Tier 3 1 2,100 286 2,040 81 1,390

1 Values for Tier 3 calculated using Equation 1

.

### 4 Corresponding results for NO x 

### are presented in Table 3. In c ontrast to HC and CO, the values for Bin 2 were adopted for Tier 3, as the FT P composite of 5.5 mg/mi suggests that Bin-2 vehicles can meet the “effectiv e standard” of 10 mg/mi with a reasonable compliance margin.

Table 3. NOx: Useful-Life FTP Standards and Associated Cold-Start and Hot-Running Results on the FTP and US06 Cycles.

Bin Useful-lifeStandard (mg/mi) FTP Composite (mg/mi) Cold Start (mg) FTP hot Running (Bag 2) (mg/mi) US06 (mg/mi)

8 200 64.2 418 35.1 61.3 5 70 21.2 165 8.2 45.9 4 40 8.7 90 4.7 30.6 3 30 5.7 71 3.8 30.6 2 20 5.5 67 0.4 18.4

Tier 3 1 10 5.5 67 0.4 18.4

### 5 1.2 Develop Phase-In Assumptions (Step 2)
We designed phase-in assumptions so as to proj ect compliance with the Tier-3 fleet average NMOG+NO x 

### requirements. The requirements are shown in Table 4 for cars and trucks. The phase-in begins in model year 2017 and ends in model year 2025.

Table 4. Target NMOG+NO x 

### Fleet Average Requirements for the Federal Test Procedure. Model year FTP Composite, NMOG+NO x 

### (g/mi)

LDV/T1 LDT2 1

2017 0.086 0.101

2018 0.079 0.092

2019 0.072 0.083

2020 0.065 0.074

2021 0.058 0.065

2022 0.051 0.056

2023 0.044 0.047

2024 0.038 0.038

2025 0.030 0.030

1 Throughout, these results app lied to Federal truck classes LDT2, LDT3 and LDT4.



### These results are also pictured in Figure 1. No te the sharp drop in emi ssions at the outset of the Tier-3 phase-in, also that the truck requirements (LDT2,3,4) are slightly higher than those for the lighter vehicles (LDV-T1). After 2017, the reduc tion in the fleet average is linear, and at the completion of the phase-in, fleet averages for cars and truc ks no longer differ.

### 6 Figure 1. NMOG+NO x 

### FTP Fleet Average Requirements du ring Phase-In of the Tier-3 Exhaust Emissions Standards for Light-Duty Vehicles.
In development of MOVES rates we translated the fleet requirements so as to develop phasein assumptions representing the introduction of Ti er-3 vehicles and concurrent replacement of Tier-2 vehicles. For purposes of model input development, we project phase-ins for four categories of Federally-certified vehi cles, LDV-T1, LDT2, LDT3 and LDT4.
These phase-in fractions give emission rates that reproduce the fleet requirements when FTP composites are calculated by combining start and running rates. To represent the fleet requirements, the phase-in assumptions are “linear” and “proportional.”
By “linear” we mean that the fractions of Ti er-2 vehicles, whether taken all together, by vehicle class or by Bin, decline lin early during the phase-in period. We represent them this way because the fleet requirements also decline linearly.
By “proportional,” we mean that during the phase -in, the various bins within a vehicle class maintain the same relative proportions as in MY 2016, at the outset of the phase-in. For example, in 2016, we assume that 89% and 3.5% of LDV-T1 vehicles are in Bins 5 and 3, respectively. This difference implies that the fleet comprises 25.43 times as manyBin-5 vehicles as Bin-3 vehicles (0.89/0.035). Th is ratio holds in any given model year duri ng the phase-in. In MY 2023, the remaining fractions of Bin 5 and Bin 3 are 10.18% and 0.40%, which give the same ratio as in MY 2016. The same proportiona l approach was applied to LDT2, LDT3 and LDT4. Phase-in assumptions, expressed as the re lative composition of Bins within each vehicle class, are presented in Figure 2 through Figure 5. 0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160 0.180201520162017201820192020202120222023202420252026FTPCompositeStandard(g/mi)



## Model Year LDV/LDT1

LDT234

### 7 Figure 2. Phase-in Assumptions, by St andard and Bin, for LDV-T1 Vehicles.

Figure 3. Phase-in Assumptions, by St andard and Bin, for LDT2 Vehicles.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%2016201720182019202020212022202320242025RelativeComposition(%)



## Model Year T3

Bin 2

Bin 3

Bin 4

Bin 5

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%2016201720182019202020212022202320242025RelativeComposition(%)



## Model Year T3

Bin 3

Bin 4

Bin 5

### 8 Figure 4. Phase-in Assumptions, by St andard and Bin, for LDT3 Vehicles.

Figure 5. Phase-in Assumptions, by St andard and Bin, for LDT4 Vehicles. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%2016201720182019202020212022202320242025RelativeComposition(%)



## Model Year T3

Bin 4

Bin 5

Bin 8

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%2016201720182019202020212022202320242025RelativeComposition(%)



## Model Year T3

Bin 5

Bin 8

### 9 1.3 Merge Cycle Results and Phase-In Assumptions (Step 3)
The goal of this step is to calculate weighted averages of the FTP (cold-start and hot-running) results for all standards in each model year, with the emissions results weighted by applicable phase-in fractions. We do this step for each vehicle class separately, then weight the four truck classes together using a set of fractions derived from the weighted sales estimates.
Figure 6 shows an example of the phase-in calculation for NO x 

### from cars between model years 2016 and 2025. The figure shows cold-start and hot-running FTP values for Tier-1, Tier-2 and Tier-3 standards, as well as the phase-in fractions for each standard in each model year. Start and running emissions in each model year are simply calculated as weighted averages of the emissions estimates and the phase-in fractions . The resulting weighted start estimates are used directly to represent cold-start emissions for young vehicles in each model year (ages 0-3). For running emissions, however, the av erages are not used directly; rather, each is expressed as a ratio to the corresponding Tier-1 value.
Table 5 shows weighted average values for model-years 2016-2025 for simulated FTP composites, cold-start and hot-r unning emissions. The start values , expressed as the cold-start mass increment (g), are used dire ctly in the MOVES emission rate table to represent cold-start emissions (operating mode 108). The compos ites and running emissions, expressed as rates (g/mi), are presented for comparison. For runni ng emissions, however, the averages shown in the table are not used directly; rather, each is expressed as a ratio to the corresponding Tier-1 value, as shown in Figure 7 to Figure 9 below.

Figure 6. Example of Phase-In Calculat ion, for NOx from LDV-T1, for MY 2016-2025.

Standard Cold Start Hot Running (mg) (mg/mi) 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

Tier 1 Tier 1 888.00 127.00 0 0 0 0 0 0 0 0 0 0

Bin 8 417.87 35.07 0 0 0 0 0 0 0 0 0 0 Bin 5 165.42 8.21 0.890 0.407 0.356 0.305 0.254 0.204 0.153 0.102 0.058 0 Tier 2 Bin 4 89.72 4.69 0.060 0.027 0.024 0.021 0.017 0.014 0.010 0.007 0.004 0 Bin 3 70.89 3.78 0.010 0.016 0.014 0.012 0.010 0.008 0.006 0.004 0.002 0 Bin 2 67.18 0.38 0.015 0.007 0.006 0.005 0.004 0.003 0.003 0.002 0.001 0

Tier 3 Tier 3 67.18 0.38 0.000 0.543 0.600 0.657 0.714 0.771 0.829 0.886 0.935 1.000

Cold Start (mg) 154.32 107.85 102.76 97.69 92.60 87.52 82.43 77.35 72.99 67.18

Hot Running (mg/mi) 7.64 3.74 3.32 2.90 2.48 2.06 1.64 1.22 0.86 0.38
RATIO to Tier 1 0.0601 0.0295 0.0262 0.0228 0.0195 0.0162 0.0129 0.00961 0.00677 0.00299 Phase-In by Model Year

### 10 Table 5. Weighted Average FTP Values Pr ojected for Trucks and Cars for MY 2017-2025.
regClass MY CO HC NOx Composite (mg/mi) Start (mg) Running (mg/mi) Composite (mg/mi) Start (mg) Running (mg/mi) Composite (mg/mi) Start (mg) Running (mg/mi)

Ref. 1 1,620 11,400 805 126 1,530 57.1 209 888 12.7

Trucks 2017 455 3,855 166 22.4 368 2.97 14.2 121 5.04 2018 434 3,625 155 20.7 341 2.76 13.1 114 4.45 2019 412 3,395 144 19.0 314 2.54 12.0 108 3.86 2020 391 3,164 134 17.3 287 2.32 10.9 101 3.27 2021 369 2,934 123 15.7 260 2.10 9.82 93.9 2.68 2022 348 2,704 112 14.0 233 1.88 8.72 87.0 2.09 2023 327 2,474 101 12.3 206 1.66 7.62 80.2 1.50 2024 305 2,246 91 10.7 179 1.45 6.53 73.4 0.914 2025 286 2,037 81 9.2 154 1.25 5.54 67.2 0.380 Cars 2017 426 3,566 149 20.5 339 2.70 12.0 108 3.74 2018 408 3,375 140 19.1 316 2.52 11.2 103 3.32 2019 3991 3,184 132 17.7 293 2.34 10.4 97.7 2.90 2020 373 2,993 123 16.3 270 2.16 9.60 92.6 5.48 2021 356 2,802 115 14.8 247 1.97 8.77 87.5 2.06 2022 338 2,610 106 13.4 224 1.79 7.96 82.4 1.64 2023 321 2,419 98 12.0 201 1.61 7.16 77.4 1.22 2024 306 2,255 91 10.8 181 1.46 6.46 73.0 0.860 2025 286 2,037 81 9.2 154 1.25 5.54 67.2 0.380

1 The reference level repr esents Tier-1 LDV-T1.

### 11 Figure 7. Weighted Ratios for Composite, Start and Running CO Emissions, for (a) Trucks and (b) Cars. 0.206 0.193 0.179 0.166 0.153 0.139 0.126 0.113 0.101

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40201720182019202020212022202320242025WeightedRatio



### Model Year Composite

Cold Start

Hot Running

0.185 0.174 0.164 0.153 0.143 0.132 0.122 0.113 0.101

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35201720182019202020212022202320242025WeightedRatio



### Model Year Composite

Cold Start

Hot Running 

## (a) Trucks

(b) Cars

### 12 Figure 8. Weighted Ratios for Composite, Start and Running THC Emissions, for (a) Trucks and (b) Cars. 0.052 0.048 0.044 0.041 0.037 0.033 0.029 0.025 0.022 0.00 0.05 0.10 0.15 0.20 0.25 0.30201720182019202020212022202320242025WeightedRatio



### Model Year Composite

Cold Start

Hot Running

0.047 0.044 0.041 0.038 0.035 0.031 0.028 0.026 0.022 0.00 0.05 0.10 0.15 0.20 0.25201720182019202020212022202320242025WeightedRatio



### Model Year Composite

Cold Start

Hot Running 

## (a) Trucks

(b) Cars

### 13 Figure 9. Weighted Ratios for Composite, Start and Running NOx Emissions, for (a) Trucks and (b) Cars. 0.040 0.035 0.030 0.026 0.021 0.016 0.012 0.007 0.003 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16201720182019202020212022202320242025WeightedRatio



### Model Year Composite

Start

Hot Running 

## (a) Trucks

0.029 0.026 0.023 0.020 0.016 0.013 0.010 0.007 0.003 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14201720182019202020212022202320242025WeightedRatio



### Model Year Composite

Cold Start

Hot Running 

## (b) Cars

### 14 1.4 Estimating Emissions by Operating Mode (Step 4)
To project emissions for Tie r-2 and Tier-3 vehicles, we divided the operating modes for running exhaust into two groups. These groups repr esent the ranges of sp eed and power covered by the hot-running phase (Bag 2) of the FTP stan dards (< ~20 kW/Mg), and the ranges covered by the SFTP standards (primarily the US06 cycl e). For convenience, we refer to these two regions as “the hot-running FTP region” and “US 06 region,” respectively (See Figure 10). Data measured on the SC03 cycle did not play a role in emission rate development.
To estimate emissions by operating mode, the a pproach was to multiply the emission rates for MY 2000, representing Tier 1, by a specific ratio for each model year from 2016 to 2025, to represent emissions for that model year. Fo r the FTP operating modes, we applied the ratios shown in Figure 7 to Figure 9 above.
To estimate rates for the US06 modes, we followe d a procedure similar to that for the “FTP” modes, but using the “US06” columns in Tabl e 1 through Table 3. For HC and CO, we used Equation 1, as before. For NO x 

### , we applied the Bin-2 values. Figure 11 through Figure 13 show fractional reductions in the US06 rates along with similar reductions in hot-running operation, relative to levels for MY 2000 cars (Tier-1 levels). Note that the trends for “hot-running” are identical to those in Fi gure 7 through Figure 9.
Figure 14 and Figure 15 show app lication of the ratios to th e FTP and US06 operating modes in model years 2010, 2017, and 2025, representing fully phased-in Tier-2 standards, an interim year during the Tier-3 phase-in, and the fully phased-in Tier-3 st andards, respectively. Rates for all three years are calculated with respect to rates for cars in model-year 2000, using reduction ratios shown above in Figure 11 through Figure 1 3, applied to rates in all operating modes for running operation. In these figures, the result s are presented on both linear and logarithmic scales. The linear plots display the differences in the high-power modes, but obscure those in the low-power modes. The logarithmic plots supp lement the linear plots by making visible the relatively small differences in the lower power mode s. They also illustrate the varying degrees of control between the “hot-running FTP” (< 20 kW/Mg) and the “US06” (> 20 kW/Mg) modes. In addition, the logarithmic plots include the level for MY2000, which represents Tier-1 standards. Thus, these plots display the degree of running- emissions reduction between Tier1 and Tier 2 (MY2000: MY2010), and between Tier 2 and Ti er 3 (MY2010: MY2025), across the full range of vehicle-specific power. Note that for simplic ity, these figures represent rates for operating modes 21-30, covering a wide range of power for vehicles oper ating at speeds between 25 and 50 mph.

### 15 Figure 10. Operating modes for running Exhaus t Emissions, divided broadly into “hotrunning FTP” and “US06” regions.Vehicle-Specific Power (kW/tonne)

The “hot-running FTP Region” Low to Moderate Power (also includes braking (0) and idle (1) The “US06 Region” High Power

### 16 Figure 11. CO: Weighted Ratios for Cars, for hot-running emissions, representing the “hot-running FTP Region” (FTP) and the “US 06 Region” (US06), for (a) Trucks and (b) Cars. 0.206 0.193 0.179 0.166 0.153 0.139 0.126 0.113 0.101 0.488 0.459 0.431 0.402 0.374 0.346 0.317 0.289 0.263

0.00 0.10 0.20 0.30 0.40 0.50 0.60201720182019202020212022202320242025WeightedRatio



### Model Year Hot Running

US06

0.185 0.174 0.164 0.153 0.143 0.132 0.122 0.113 0.101 0.392 0.376 0.360 0.344 0.328 0.311 0.295 0.282 0.263

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45201720182019202020212022202320242025WeightedRatio



### Model Year Hot Running

US06 

# (a) Trucks

(b) Cars

### 17 Figure 12. THC: Weighted Rati os for Cars, for hot-running emissions, representing the “hot-running FTP Region” (FTP) and the “US 06 Region” (US06), for (a) Trucks and (b) Cars. 0.052 0.048 0.044 0.041 0.037 0.033 0.029 0.025 0.022 0.327
0.298
0.269
0.240
0.211
0.182
0.153
0.124 0.098

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35201720182019202020212022202320242025WeightedRatio



### Model Year Hot Running

US06

0.047 0.044 0.041 0.038 0.035 0.031 0.028 0.026 0.022 0.211 0.197 0.183 0.169 0.155 0.140 0.126 0.114 0.098

0.00 0.05 0.10 0.15 0.20 0.25201720182019202020212022202320242025WeightedRatio



### Model Year Hot Running

US06 

## (a) Trucks

(b) Cars

### 18 Figure 13. NOx: Weighted Rati os for Cars, for hot-running emissions, representing the “hot-running FTP Region” (FTP) and the “US 06 Region” (US06), for (a) Trucks and (b) Cars. 0.040 0.035 0.030 0.026 0.021 0.016 0.012 0.007 0.003 0.168 0.154 0.140 0.127 0.113 0.099 0.086 0.072 0.060

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18201720182019202020212022202320242025WeightedRatio



### Model Year Hot Running FTP

US06

0.029 0.026 0.023 0.020 0.016 0.013 0.010 0.007 0.003 0.098 0.094 0.089 0.084 0.079 0.074 0.070 0.065 0.060

0.00 0.02 0.04 0.06 0.08 0.10 0.12201720182019202020212022202320242025WeightedRatio



### Model Year Hot Running FTP

US06


## (b) Cars

(a) Trucks

### 19 Figure 14. Projected Emission Rates for Ca rs in Operating modes 21-30, vs. VSP, in ageGroup 0-3 years, for three model years, for (a) CO, (b) THC and (c) NOx (LINEAR SCALE). 0 100 200 300 400 500 600 700 800 900 1,000

-5 0 5 10 15 20 25 30 35 40Emission Rate (g/hr)

Vehicle Specific Power (kW/Mg) 2010
2017
2025

0 1 2 3 4 5 6 7

-5 0 5 10 15 20 25 30 35 40Emission Rate (g/hr)

Vehicle Specific Power (kW/Mg) 2010
2017
2025

0 2 4 6 8 10 12 14 16 18

-5 0 5 10 15 20 25 30 35 40Emission Rate (g/hr)

Vehicle Specific Power (kW/Mg) 2010
2017
2025 

## (b) THC

(c) NOx (a) CO

### 20 Figure 15. Projected Emission Rates for Ca rs in Operating modes 21-30, vs. VSP, in ageGroup 0-3 years, for Four Model Years, for (a) CO, (b) THC and (c) NOx (LOGARITHMIC SCALE). 0.01 0.10 1.00 10.00 100.00

-10 0 10 20 30 40Emission Rate (g/hr)

Vehicle Specific Power (kW/Mg) 2000
2010
2017
2025

0.001 0.010 0.100 1.000 10.000 100.000 1,000.000

-5 0 5 10 15 20 25 30 35 40Emission Rate (g/hr)

Vehicle Specific Power (kW/Mg) 2000
2010
2017
2025 

### (c) NOx 1 10 100 1,000 10,000

-10 0 10 20 30 40Emission Rate (g/hr)

Vehicle Specific Power (kW/Mg) 2000
2010
2017
2025 

### (a) CO

(b) THC

### 21 1.5 Apply Deterioration (Step 5)
Based on review and analysis data from the Phoenix Inspection-and-Maintenance Program, we assume that deterioration for different t echnologies is best represented by a multiplicative model, in which different technologies, repr esented by successive model-year groups, show similar deterioration in relative terms but markedly different deterioration in absolute terms. We implemented this approach by translating emissi ons for the 0-3 age Group, as calculated above, into their respective logarithmic means and a pplying uniform logarithmic age trends to all model-year groups. We derived logarithmic dete rioration slopes for Ti er-1 vehicles (MY 1996- 98) and applied them to Tier-2 vehicles. In this process we applied the sa me logarithmic slope to each operating mode, which is an extension of the multiplicative deterioration assumption.
For Tier-3 vehicles, the deterioration assumptions were modified to represent an extension of the full useful life (FUL), which is increased from 120,000 mi to 150,000 mi. The extension of the useful life, which assumes improved dur ability, was expressed through a reduction in deterioration.
To represent improved durability, differential reductions were applied to logarithmic deterioration for THC and NO x 

### . These reductions were applied such that when FTP composites were reconstructed from the resulting emission start and running emission rates, the reduction in deterioration was proportional to the increase in the us eful life. The reducti ons achieving this goal were 27% and 14% for THC and NO x 

### , respectively.

Note that in the reconstructi on of FTP composites for NMOG+NO x 

### , values for NMOG were estimated from those for THC. In this step the fraction of THC repr esenting NMOG for start emissions was higher than that for running emissions 2 

### . In addition, start deterioration for THC (and NMOG) followed lower relative rates than running deterioration, wh ereas start and running NO x 

### emissions deteriorate at the sa me relative rates (sec. 1.4.3).
Results are shown in Figure 16. In MOVES, dete rioration is expressed in terms of vehicle age, rather than mileage. However, assu ming typical mileage accumulation of 10,000 to 15,000 miles per year, we assume that vehicles reach the end of their useful lives between 10 and 15 years of age, or between the 8- 9 year and the 10-14 year ageGr oups. Accordingly, deterioration for THC and NO x 

### was modified so that the value of NMOG+NO x 

### reached in the 8-9 year ageGroup under a 120K FUL assumption, would be reached in the 10-14 year ageGroup under a 150K FUL assumption. Note that in that plot th e value for each ageGroup is assigned to the midpoint of the group, i.e., the valu e for the 8-9 year ageGroup is shown at 9 years, and that for the 10-14 year ageGroup is shown at 12.5 years.
We do not assume that emission rates for young vehicles, i.e., in th e 0-3 year ageGroup, would differ under either assumption, as vehicles m eet the same levels at certification. Thus, the deterioration trends for the two cases diverge as th e vehicles age. We assu me that the most rapid changes in fleet means occur during the first 10 y ears of life, or between the 0-3 year ageGroup

2 For start emissions, NMOG = 0.89×THC, and for running emissions NMOG = 0.57×THC.

### 22 and the 8-9 year ageGroup. After th at point, we assume that the rate of change declines as the fleet means tend to stabilize (especially in I/M ar eas, which are represented in the plot). The ratio between values for the 150K FUL and 120K FU L starts at 1.0 and declines, stabilizing at a value of 0.85 in the 8-9 year ageGroup, and rema ining constant thereafter. Accordingly, we assume that the around the end of the useful life, mean FTP emissions for vehicles certified at 150K mi would be approximately 85% of those certified at 120K mi.

Figure 16. Simulated FTP composites for NMOG+NO x 

### , calculated from MOVES start and running rates, under 120K and 150K FUL assumptions.

1.5.1 Recalculate the logarithmic mean
Starting with the values of the arithmetic mean ( x a 

### ) calculated in steps 1-4, we calculate a logarithmic mean ( x l 

### ), as shown in Equation 2.

2 ln 2 l
a l 

### x x 

  Equation 2



### The logarithmic variance expresses the degree of skewness in the distribution of emissions, as the difference between the arithmetic mean and the geometric mean, of which the arithmetic mean is always larger. We assume that this te rm changes over time, re flecting differing degrees in the relative skewness of the underlying emissions distribu tions as vehicles age (Table 7 below). The values of the logarithmic variance σ l 2 

### are intended to represent values for young vehicles, as the estimates for x a 

### represent the 0-3 year age Group. The values of σ l 2 

### used for this

### 23 step were 1.30, 0.95 and 1.60 for CO, THC and NO x 

### , respectively, as used in developing default rates for MOVES2010.

1.5.2 Apply a logarithmic Age slope
After estimating logarithmic m eans for the 0-3 age class ( x l ,0-3 

### ), we estimate additional logarithmic means for successive age classes ( x l ,age 

### ), by applying a linear slope in ln-space ( m l 

### ).

1.5)

- age ( 3 0
, age , l l l 

### m x x  

 Equation 3



### The values of the logarithmic slope are adap ted from values developed for the 1996-98 model –year group. The values applied to Tier-2 and Tier-3 vehicles are shown in Table 6. The reduced slopes for Tier-3 were calculated by redu cing the Tier-2 values by 27% for HC and CO and by 14% for NO x 

### . When calculating the age inputs for th is equation, we subtracted 1.5 years to shift the intercept to the midpoint of the 0-3 year age Gr oup, as shown in Equation 3.
Table 6. Values of the logarithmic deteriorat ion slope applied to running-exhaust emission rates for MY following 2000. Pollutant Operating-Mode Group Logarithmic Slope ( m l )

Tier 2 Tier 3
CO “hot-running FTP” 1 0.13 0.0949

“US06” 2 0.06 0.0438
THC “hot-running FTP” 0.09 0.0657

“US06” 0.09 0.0657

NO x “hot-running FTP” 0.15 0.129

“US06” 0.15 0.129

1 Includes opModeID = 0,1, 11-16, 21-25, 27, 33,35,37.

2 Includes opModeID = 28,29,30, 38,39,40.



### 1.5.3 Apply the reverse transformation
After the previous step, the values of x l ,age 

### were reverse-transformed, as in Equation 4, where Y

is the emission rate in “linear space,” (g/hr) and s l 2 

### is the logarithmic vari ance. The values of the logarithmic variance used for this step we re adapted from the Phoe nix I/M results and are

### 24 intended to represent emissions distributions fo r “real-world” vehicle pop ulations, meaning that the values are higher than those listed above a nd may vary with age. Values of logarithmic variances for all three polluta nts are shown in Table 7.

2 age , 5

. 0 ln 

## e e l l s x 

## Y  Equation 4



### Table 7. Values of Logarithmic Variance Used to Calculate Emi ssions Deterioration by Reverse Transformation of Logarithmic Means.
Age Group Pollutant

CO THC NO x 0-3 years 1.30 0.95 1.60

4-5 2.05 1.50 1.60

6-7 2.00 1.70 1.40

8-9 1.80 1.90 1.40



### Note that no values are presented in the ta ble for the 10-14, 15-19 and 20+ year age Groups. This omission is intentional, in that we did not want to extrapol ate the deterioration trend beyond the 8-9 year age Group. Extrapolation beyond this point is incorrect, as we know that emissions tend to stabilize beyond this age, while the ln-linear emissions m odel would project an increasingly steep and unrealis tic exponential emissions trend. For the 10-14, 15-19 and 20+ age Groups, the “stabilizatio n of emissions with age” was es timated as for MOVES2010 (section 1.3.3.7).
Note that the “stabilization” is applied independe ntly to the deterioration trends for Tier-2 and Tier-3 vehicles. The trends in Figure 16 show that the relative differences or ratios between the 8-9 year values and those for the three successi ve ageGroups are the same for both Tier-2 and Tier-3 vehicles.

1.6 Estimate non-I/M References (Step 6)
Completion of the preceding steps provided a set of rates repres enting I/M reference rates for MY 2016-2025. As a final step, we estimated no n-I/M reference rates by applying the same ratios applied to the I/M references fo r default rates in MOVES2010 (section 1.3.3.6).

1.7 Start Emissions

The values for “FTP Cold-start” shown in Tabl e 5 above were used to represent cold-start emissions (opModeID=108). Rates for “warm” or “hot” starts following a range of soak periods

### 25 were estimated as in MOVES2010 (see 1.4.2). De terioration was applied to start emissions, relative to that for running emissi ons, also as in MOVES2010 (see 1.4.3).

1.8 Deterioration and the Bene fits of Warranty Extension
EPA is proposing to provide manufacturers an NMOG+NO x 

### credit of 5 mg/mi, which can be applied to certification emissions levels for sp ecific test groups in the calculation of fleet averages. The credit can be applied a test gr oup if the manufacturer a ssumes the liability of warranting their emissions-related components a nd systems for the enti re useful life of 150,000 miles. This warranty period is considerably l onger and the proposed warranty more robust than the primary EPA emissions warranty, which expire s at 80,000 miles of ope ration and applies to fewer components and systems.
To estimate the size of the anticipated bene fit to the environment due to extending the warranty for emissions controls we can reexamine the fleet average trends presented in Figure 16 above, although for purposes of this discussion we will assume that they apply to a single test group rather than to the fleet as a whole. In considering the wa rranty, we compared the values of the mean at the end of the primary warranty (80,000 miles) and at the end of the useful life (150,000 miles). We assume that vehicles in the test group tend to re ach 80,000 miles at about 10 years of age and 150,000 miles at about 13 years of age, and we further assume that the continued operation of the warranty would neut ralize any additional increase in the test group mean. i.e., the emissions trend would be level afte r 10 years of age. On this basis, we estimate that the difference between the mean at 80,000 m iles (the maximum with a full-life warranty) and the mean at 150,000 miles (assuming emissions continued to deteriorate without the warranty) is about 6 mg/mi. Thus, the emissi ons benefit attributable to the extended 150,000- mile warranty is projected to exceed the proposed 5 mg/mi credit for NMOG+NO x 

### .

i US. EPA. Office of Tran sportation and Air Quality. Development of Emission Rates fo r Light-Duty Vehicles in the Motor Vehicle Emissions Simulator (MOVES2010): Final Report . (EPA-420-R-11-011) Assessment and Standards Division, Ann Arbor, MI. August, 2011. http://www .epa.gov/otaq/models/moves/documents/420r11011.pdf.