1

 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 ANN ARBOR, MI 48105

 

September 10, 2010

 OFFICE OF

AIR AND RADIATION

MEMORANDUM

SUBJECT: PROCESS FOR DETERMINING CLASS 2B AND 3 CO2 STANDARD

FROM: A. Neam, J. Cherry, Assessment and Standards Division

TO: Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for 

Heavy-Duty Engines and Vehicles; Docket Number EPA-HQ-OAR-2010-0162

1 Introduction

The heavy duty (class 2b and class 3) pickup trucks and vans sold currently in the United 

States, and those which are anticipated to be sold in the MY 2014-2018 timeframe, are 

highly varied and satisfy a wide range of needs. Examples for these vehicle classes 

include vans that can transport 15 passengers and pickup trucks that can tow over 20,000 

pounds. American consumers require many vehicle options to accommodate their utility

needs and preferences. Recent volatility in oil prices and the state of the economy have 

demonstrated that consumer demand and choice of vehicles within this wide range can be 

sensitive to these factors. Although it is impossible for any organization to precisely 

predict the future, a characterization and quantification of the future fleet are required to 

assess the impacts of rules which would affect that future fleet. The historic 

perturbations in the U.S. economy and especially in the automotive sector in recent years 

make such forecasting particularly problematic, and so for this rulemaking, it is assumed 

the future mix of heavy duty trucks and vans, and volumes of heavy duty vehicles, will be 

the same as those in the 2008 model year, the most recent relatively stable sales year. In 

order to accomplish this, manufacturers have provided details on their 2008 models and 

volumes. This data along with available emissions data was used to determine the 

baseline fleet. This document provides details of how the baseline fleet was created, how 

the CO2 emissions for each vehicle was determined, how the baseline and standard 

emissions curves for the fleet were determined, and gives the phase in for the standard.
2

1.1 Why do the agencies establish a baseline vehicle fleet?

In order to calculate the impacts of proposed standards, it is necessary to estimate the 

composition of the future vehicle fleet absent the standards in order to conduct 

comparisons. We have developed a comparison fleet. The first step in this process was 

to develop a baseline fleet based on model year 2008 data. EPA and NHTSA created a 

baseline fleet in order to track the volumes and types of fuel economy-improving and 

CO2-reducing technologies which are already present in today’s fleet. Creating a 

baseline fleet helps to keep, to some extent, the agencies’ from adding technologies to 

vehicles that already have these technologies, which would result in “double counting” of 

technologies’ costs and benefits when modeling. 

1.2 The 2008 baseline vehicle fleet

1.2.1 Why did the agencies choose 2008 as the baseline model year?

The 2008 model year is the most recent model year for which the industry had normal 

sales. The 2009 model year data was available, but this model year was disrupted by the 

economic downturn and the bankruptcies of both General Motors and Chrysler. There 

was a significant reduction in the number of vehicles sold by both companies and the 

industry as a whole. These abnormalities made the 2009 model year data unsuitable for 

use as a future fleet. Therefore, the agencies chose to use the 2008 model year data as the 

baseline since it was the latest representative transparent data set available. 

1.2.1.1 On what data is the baseline vehicle fleet based?

EPA used several sources to determine the composition, volumes, and emissions of the 

vehicles in the fleet. Though the composition and volumes of the fleet are from the 2008 

model year, some advances in fuel economy technology have occurred since the 2008 

model year, so emissions data from newer vehicles (when available) was used to model 

the emissions of the vehicles. Representative emissions data from the 2008, 2009, and 

2010 model year’s vehicles was used.

The source of the heavy duty fleet composition and volumes are the automotive 

manufacturers. Chrysler, Ford, and General Motors each submitted product plans which 

included their fleet composition, details of each unique (weight and capability) truck and 

van sold, and their volume. The manufacturers included the 2008 model year at the 

agency’s request.

There were two sources for the CO2 emissions data. The first was emissions data 

submitted by the manufacturers at vehicle certification. Manufacturers are required to 

submit city cycle emissions data when they certify vehicle for sale in Federal states. 

Manufacturers are also required to submit highway cycle emissions data for vehicles that 

are certified for sale in California. Since not all vehicles were certified for California 

sale, only a subset of emissions data was available from the certification database.
3

The second source for CO2 emissions data is a test program run by EPA. EPA tested a 

number of vehicles to acquire data from vehicles that are currently in service. The 

vehicles chosen augmented the certification data, to insure adequate CO2 values were 

available for modeling the 2008 model year fleet.

1.2.1.2 How were the 2008 vehicles CO2 emissions modeled?

Ideally, the light duty CAFE ADFE approach would have been used, but the necessary

data is not available for each heavy duty vehicle. Also, many years worth of fuel 

economy data was analyzed to determine the coefficients of the light duty equation. 

Since the method that is used for CAFE was not available, a new method was derived. 

The 2008 model year vehicles CO2 emissions were modeled using characteristics of each 

vehicle that relate to CO2 performance. Although other characteristics affect CO2

performance, the characteristics available were test weight, axle ratio, and 4 wheel drive 

vs. 2 wheel drive. 

In order to model vehicle CO2 emissions, data was acquired from both the certification 

database and the test program that match the vehicle type (truck or van), class (2b or 3), 

and engine. Multiple vehicles were examined to determine a factor that could be used 

with each of the characteristics that were used to model CO2 emissions.

Two equations were determined, one for City CO2 and one for highway CO2.

They are as follows:

City CO2= {A + [(C-B) * D]} * { 1 + [((E/F)-1) * G]} + H

Where:

A=Base City CO2

B=Test_Vehicle_Test Weight

C=CurrentVehicles Test Weight

D=Weight Multiplier City

E=Vehicle Axle Ratio

F=TestVehicleAxle Ratio

G=City Axle Multiplier

H= 0 if test and current vehicle have the same wheel drive

 = – City 2wd4wd Adder if test vehicle had 4wd and the current vehicle has 2wd 

 =+ City 2wd4wd Adder if test vehicle had 2wd and the current vehicle has 4wd

Highway CO2= {I + [(C-B) * J]} * { 1 + [((E/F)-1) * K]} + L

Where:

I=Base Highway CO2

B=Test_Vehicle_Test Weight

C=CurrentVehicles Test Weight

J=Weight Multiplier City
4

E=Vehicle Axle Ratio

F=TestVehicleAxle Ratio

K=Highway Axle Multiplier

L= 0 if test and current vehicle have the same wheel drive

 = – Highway 2wd4wd Adder if test vehicle had 4wd and the current vehicle has 2wd 

 =+ Highway 2wd4wd Adder if test vehicle had 2wd and the current vehicle has 4wd

Combined CO2 is used to set the standard. It is derived using the following equations:

Combined CO2 =55% * City CO2 + 45% * Highway CO2

1.3 The MY 2014-2018 Standards

Heavy duty vehicles are required for many applications that are beyond the capabilities of 

vehicles from the light duty fleet. It is important that the CO2 standard for heavy duty 

vehicles does not prevent them from continuing to satisfy these needs. The baseline data 

set used for the 2014-2018 model year standards was analyzed in many ways to 

determine the best way to create a baseline and ultimately a standard. 

1.3.1 What criterion was examined for determining the Baseline?

In order to preserve the utility of heavy duty vehicles, many criteria were evaluated to 

determine the input for the baseline equation. Examples include EPA curb weight, 

ALVW, Payload, GCW, GVWR, Footprint, and Trailer Tow. The definition for each is 

below.

EPA curb weight = curb weight of the vehicle with 33% of the optional content added.

ALVW = EPA curb weight + 1⁄2 Payload

Payload = GVWR - EPA curb weight

GVWR = Gross Vehicle Weight Rating,

GCWR = Gross Combined Weight Rating

Footprint = Wheelbase – (Front Track Width + Rear Track Width) / 2

Trailer Tow = GCWR-GVWR

1.3.2 How was the criterion chosen for the Baseline?

The main applications for heavy duty vehicles include hauling payload/people and/or 

towing. Most of the criteria were evaluated graphically with the exception of footprint. 

After reviewing the footprint data, it was obvious that footprint did not track well with 

CO2 and the capability of heavy duty vehicles. 
5

CO2 was graphed vs. EPA curb weight, and it was observed that at the same weight, 

vehicles can vary several hundred grams per mile of CO2. This is due to the fact that at 

the same curb weight, vehicles can have both different test weights (which relates to 

payload) and different towing capacities. EPA curb weight was determined to be an 

inadequate criterion to base the standard on.

CO2 was graphed vs. ALVW, and a more linear relationship was observed in comparison 

to the graph using EPA curb weight. There was still large variation in CO2, due to the 

fact of not capturing the capability of the vehicle completely. ALVW was determined to 

be an inadequate criterion to base the standard on.

CO2 was graphed vs. payload, and the graph was not linear. A large variation in CO2 was 

observed, due to the fact of not capturing the capability of the vehicle completely. 

Payload is not a good criterion to base the standard on.

CO2 was graphed vs. GCWR, and the graph was linear, but at the same GCWR vehicles 

can have very different CO2. The large variation in CO2 showed that GCWR does not 

completely capture the capability of a vehicle. GCWR was determined to be an 

inadequate criterion to base the standard on.

CO2 was graphed vs. GVWR, and the graph was linear, but like GCWR at the same 

GVWR, vehicles can have very different CO2. The large variation in CO2 indicated that 

GVWR does not completely capture the capability of a vehicle. GVWR was determined 

to be an inadequate criterion to base the standard on.

These vehicle attributes individually did not adequately capture the capability of the 

heavy duty vehicles. The EPA also looked at a measure of capability that is a 

combination of attributes. It is called the “Work Factor” of the vehicle. The work factor 

is defined as .75 * (payload +500 if 4wd) +. 25 * towing. Work factor gives a very linear 

graph with CO2. There are some outlier vehicles, but overall it was determined to be the 

best measure of capability.

1.3.3 How was the Baseline stringency determined?

To determine the baseline level of stringency, a curve was determined using the baseline 

CO2 data. The data was analyzed based on the criterion (work factor) calculated in the 

previous section. It was necessary to analyze the baseline using a linear line fit given that 

it is one of our goals not to eliminate vehicles in this category. Using a linear line fit 

gives equal weighting to each vehicle configuration ensuring that no vehicle 

configuration dominated the standard whether it has high or low CO2 given its work 

factor.

The linear fit produces the equation:

CO2= 0.0489 * (Work Factor) + 377

Baselines for future standards may be created using production weighting. Production 

weighting will give greatest weight to vehicles with the largest production. This is a 

good method when a fleet’s demand is well known, but given the uncertainty with the 

current fleet, it is best to use a linear line fit. 
6

1.3.4 How was the Baseline used to determine the Standard?

To determine a standard, CO2 reducing technologies for this segment were reviewed. It 

was determined that different technologies applied to gas vehicles than to diesel vehicles. 

There were more CO2 technologies available for diesel vehicles than gas vehicles. This 

led to two different percent CO2 reductions, and separate standards for the gas and diesel 

vehicles. A 15 percent reduction is possible for diesel vehicles given the technology

currently on vehicles in the baseline and the CO2 reducing technologies available. A 10 

percent reduction is possible for gas vehicles given the technology currently on vehicles 

in the baseline and the CO2 reduction technologies available. 

Using these percentages, separate standards were determined for gas and diesel vehicles.

The final standard for gas has the equation:

CO2= 0.0440 * (Work Factor) + 339

The final standard for diesel has the equation:

CO2= 0.0416 * (Work Factor) + 320

1.3.5 What is the phase in for the Standard?

The phase in percentages (shown in Table 1.3-1 Phase in Percentages) are the same for 

both the gasoline and diesel standard.

Table 1.3-1 Phase in Percentages

Year Phase-In Percentage

2014 15%

2015 20%

2016 40%

2017 60%

2018 100%

Table 1.3-2 Diesel CO2 Standard Equations) shows how the standard is phased in for 

diesel vehicles.

Table 1.3-2 Diesel CO2 Standard Equations

Year Equation

2014 CO2= 0.0478 * (Work Factor) + 368

2015 CO2= 0.0474 * (Work Factor) + 366

2016 CO2= 0.0460 * (Work Factor) + 354

2017 CO2= 0.0445 * (Work Factor) + 343
7

2018 CO2= 0.0416 * (Work Factor) + 320

Table 1.3-3 Gasoline CO2 Standard Equations) shows how the standard is phased in for 

gasoline vehicles.

Table 1.3-3 Gasoline CO2 Standard Equations

Year Equation

2014 CO2= 0.0482 * (Work Factor) + 371

2015 CO2= 0.0479 * (Work Factor) + 369

2016 CO2= 0.0469 * (Work Factor) + 362

2017 CO2= 0.0460 * (Work Factor) + 354

2018 CO2= 0.0440 * (Work Factor) + 339

1.3.6 How is the vehicle technology package effectiveness determined?

The individual CO2 reducing technologies are discussed in the Preamble and Chapter 3 

of the draft RIA. Each technology discussed has a range of CO2 reduction potential 

taking into account variations of implementation for class 2B and 3 vehicles. As in the 

2016 light duty final rule, the combined CO2 reduction for vehicle technology packages 

are determined using the lumped parameter model. A class 2B and 3 version of the 

lumped parameter is located in the docket.