UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY 

2565 PLYMOUTH ROAD 

ANN ARBOR, MICHIGAN 48105-2498 

OFFICE OF 

AIR AND RADIATION 

July 21, 2005 CCD-05-12 (LDVILDT/MDPV/HDV/HDEILD-AFC) 

Dear Manufacturer: 

Subject: Clean-Fuel Vehicle Standards 

This letter provides guidance on determining the equivalency of vehicle and engine 

emission standards in Code of Federal Regulations (CPR) Part 86 standards and Part 88 

standards for Clean-Fuel Vehicles. The determinations that follow may be used effective 

with the issue date of this guidance letter. 

Background 

The EPA Clean-Fuel Fleet Program (CFFP) was established by the requirements under 

Part C- Clean-Fuel Vehicles, Sections 241-246 of the1990 Clean Air Act (CAA) 

Amendments. The purpose of the CFFP was to reduce emissions in metropolitan areas 

not meeting Federal air quality standards through the use of clean alternative fuels. 1 The 

CAA prescribed exhaust emission standards for light-duty vehicles, light-duty trucks, and 

heavy-duty vehicles between 8,501lbs and 26,000 lbs GVWR? 

In response to the Clean-Fuel Vehicle (CFV) requirements of the CAA Amendments, 

EPA published regulations in 40 CPR Part 88, Subpart A, Emission Standards for CleanFuel Vehicles, and Subpart C, Clean-Fuel Fleet Program. Following the requirements in 

Sections 242, 243, and 245 of the CAA Amendments, EPA published standards for three 

vehicle classes: light-duty vehicles (LDVs), light-duty trucks (LDTs) up to 8,500 lbs 

GVWR, and heavy-duty vehicles (HDVs) between 8,501lbs and 26,000 lbs GVW. A 

CFV light-duty vehicle or light-duty truck can be classified as a transitionally low 

emissions vehicle (TLEV), low-emission vehicle (LEV), ultra low-emission vehicle 

(ULEV), or a zero emission vehicle (ZEV). Heavy-duty vehicles or engines used in 

heavy-duty vehicles are classified as low-emission vehicle (LEV), ultra low-emission 

vehicle (ULEV), inherently low-emission vehicle (ILEV) or a zero emission vehicle 

(ZEV). 

Subsequent to publishing its CFV regulations, EPA has promulgated new emission 

standards that are generally more stringent than or equivalent to the CFV emission 

1 Section 241(2) of the 1990 CAA Amendments lists the following fuel types as clean alternative fuels: 

any fuel mixture with gasoline or other fuel containing 85% or more (by volume) methanol, ethanol, or 

other alcohol, reformulated gasoline, diesel, natural gas, liquefied petroleum gas, hydrogen, and electricity. 2 Section 241(7) defines a clean-fuel vehicle as" .... a vehicle in a class or category of vehicles which has 

been certified to meet for any model year the clean-fuel vehicle standards applicable under this part for that 

model year to clean-fuel vehicles in that class or category." 

1 @ Printed on Recycled Paper 
standards for light-duty vehicles, light-duty trucks, and heavy-duty engines. These new 

EPA regulations added a new medium-duty vehicle passenger class, and also created a 

new chassis test procedure for heavy-duty vehicles. 

Vehicle and engine manufacturers continue to receive requests from fleet customers who 

desire to purchase vehicles compliant with CFV standards.3 Manufacturers have 

requested EPA guidance on how to continue to demonstrate to fleet customers that 

current standards are equivalent to or more stringent than CFV standards. 

The CFV emission standards for vehicles and engines are presented in 40 CFR Part 88 

Subpart A, sections 88.104-94 for vehicles and in 88.105-94 for heavy-duty engines. 

Current federal vehicle and engine certification emission standards are published in 40 

CFR Part 86. Specifically, light-duty vehicle, light-duty truck, and medium-duty 

passenger vehicle standards are presented in 86.1811-04 and complete heavy-duty 

vehicle emission standards are presented in 86.1816-05 and 86.1816-08. Otto cycle 

standards for the 2005-2007 model year heavy-duty engines and vehicles are presented in 

86.005-10 and in 86-008-10 for 2008 and later model years. Diesel cycle emission 

standards for 2004-2006 model year heavy-duty engines and vehicles are presented in 

86.004-11 and in 86.007-11 for 2007 and later model years. 

Determination 

To determine equivalency, current certification emission standards for Tier 2 vehicles 

(LDVs, LDTs, and MDPVs), heavy-duty vehicles, heavy duty Otto cycle engines, and 

heavy-duty diesel engines were compared to CFV vehicle and engine emission standards 

using the methodology outlined in the Attachment. The results of this analysis are 

summarized as follows: 

Tier 2 LDVs, LDT1-4s, and MDPVs certified to the following Tier 2 bin standards are 

equivalent to or more stringent than CFV LEV emission standards: 

LDV Bins 1-7 and Bin 9 

LDT1 Bins 1-7 and Bin 9 

LDT2 Bins 1-9 

LDT3 Bin 1-10 

LDT4 Bin 1-10 

MDPV Bin 1-114 

Tier 2 LDVs, LDT1-4s, and MDPVs certified to the following bin standards are 

equivalent to or more stringent than CFV ULEV emission standards: 

LDV Bins 1-3 

LDTl Bins 1-3 

LDT2 Bins 1-4 

3 Correspondence addressed to EPA from the Engine Manufacturers Association dated December 8, 2004. 

4 There are no CFV emission standards that correspond to the Tier 2 MDPV class but MDPVs meeting Tier 

2 Bins 1-ll are all equal to or more stringent than LDT4 CFV LEV standards. 

2 
LDT1 Bins 1-3 

LDT2 Bins 1-4 

LDT3 Bins 1-4 

LDT4 Bins 1-4 

MDPV Bins 1-45 

The following determinations are made for 2005 and later model year Otto cycle heavyduty vehicles: 

8,501-10,000 GVWR Otto-cycle heavy-duty vehicle chassis standards are more 

stringent than the CFV Otto cycle heavy-duty engine LEV emission standard. 

10,001-14,000 GVWR Otto-cycle heavy-duty vehicle chassis standards are more 

stringent than the CFV Otto cycle heavy-duty engine LEV emission standard. 

The following determinations are made for 2005 and later model year heavy-duty Otto 

cycle engines and diesel engines: 

Current emission standards for heavy-duty engine Otto cycle engines and diesel 

engines are more stringent than CFV LEV heavy-duty Otto cycle engines, or 

heavy-duty diesel engine emission standards. 

Compliance with EPA Standards and Program Requirements 

Manufacturers may assure fleet managers that vehicles and engines certified under 

current emission standards which EPA has determined to be as or more stringent than 

corresponding CFV emission standards meet CFV emission standards. (See the 

Determination section above for determining which current standards qualify) 

Section 40 CFR 86.1817-0S(a)(l) prohibits heavy-duty vehicles and engines labeled for 

use in clean-fuel vehicles from participating in EPA's NOx averaging, banking, and 

trading (ABT) program. Similarly, 40 CFR 86.004-15(a)(l) also prohibits CFV-labeled 

engines in heavy-duty engine families from participating in NMHC plus NOx, and 

particulate ABT. Engines that are not labeled CFV-compliant are eligible to participate 

in Part 86 ABT programs. 

This guidance document shows which Part 86 emission standards are equivalent to or 

more stringent than CFV emission standards. This document does not change any of the 

requirements of the CFFP in Part 88. Manufacturers certifying under Part 88 CFFP 

emission standards are not exempt from complying with all other CFFP requirements. 

Questions concerning CFV standards and CFFP requirements for vehicles up to 14,000 

GVWR vehicles may be directed to Martin Reineman, 734-214-4430, or 

reineman.martin@epa.gov. Questions on CFV engine standards and CFFP requirements 

may be directed to Jason Gumbs, 202-343-9271, or gumbs.jason@epa.gov. 

5 There are no CFV standards that correspond to the Tier 2 MDPV class but MDPVs meeting Tier 2 Bins 1-

4 are all equal to or more stringent than LDT4 CFV ULEV emission standards. 

3 
Attachment 

Sincerely, 

Merrylin 

~~~ Zaw-Mon, Director 

Certification and Compliance Division 

Office of Transportation and Air Quality 

4 
Attachment to CCD-05-12 

Analysis of CFV Emission Standards 

There are four issues which must be addressed in order to determine the equivalency of 

CFV standards and the federal certification emission standards: determining CFVequivalent standards for the newly-added MDPV class, equating grams per brake 

horsepower-hour standards and grams per mile standards, converting NMHC to NMOG, 

and determining equivalency for a combined NMHC+NOx CFV standard when current 

federal standards are expressed as separate NMHC and NOx standards. 

1. How to address the newly-added vehicle class of Medium-Duty Passenger Vehicle 

(MDPV). 

The newly-added class of Medium-Duty Passenger Vehicles (MDPVs) did not exist at 

the time of the CFV regulations. These vehicles include heavy-duty vehicles weighing 

less than 10,000 pounds GVWR designed primarily for carrying passengers. These 

vehicles would have been considered as heavy-duty vehicles under the CFV provisions. 

However, they would not have been tested in the same way- MDPVs are chassis-tested, 

whereas heavy-duty vehicles were engine-tested. The issue that arises from this is that 

the engine testing-based emission standards are expressed in different units than chassis 

testing-based standards, as discussed below. 

2. Converting glbhp-hr into g/mi. 

The CFV standards for heavy-duty vehicles (which, at the time were tested on engine 

dynamometers) are expressed in units of glbhp-hr. The CFV standards for light-duty 

vehicles (tested on chassis dynamometers) are expressed in grams per mile. Since the 

time of these standards, some heavy-duty vehicles are now required to be tested on 

chassis dynamometers. Also, the new class of MDPVs has g/mi standards, whereas 

under the CFV program, they would have had glbhp-hr standards. To determine if CFV 

emission standards for these vehicles are equivalent to or more stringent than the federal 

certification emission standards in effect today the glbhp-hr standards must be converted 

into g/mi. 

For engine standards in the 8,501-10,000 GVWR range (such as MDPVs), the glbhp-hr 

units are converted to g/mi units by multiplying them by the factor 1.096. For engine 

standards in the 10,001-14,000 GVWR range, convert glbhp-hr units to g/mi units by the 

factor 1.150. The CFV glbhp-hr engine emission standards for vehicles between 8,500 

and 14,000 GVWR were converted to g/mi units by using EPA-derived conversion 

factors contained in EPA Report No. EPA420-R-00-010. 1 The 1.096 and 1.150 

conversion factors referenced in this guidance letter are used solely for the purpose of 

equating Part 86 chassis test and Part 88 engine test standards for vehicles in the 8,501-

14,000 GVW range. Accurate assessment of emissions from a unique vehicle/engine 

configuration can only be accomplished by conducting dual emissions measurements 

using both chassis test and engine test procedures and protocols. 

1

This report is available on-line at www.epa.gov/otaq/regs/hd-hwy/2000frrnlr00010.pdf 

1 
3. Converting NMHC into NMOG. 

Current Tier 2 vehicle emission standards for hydrocarbons are presented as non-methane 

organic gas (NMOG); whereas CFV engine emission hydrocarbon standards are based on 

non-methane hydrocarbons (NMHC). NMOG may be converted to NMHC by use of the 

equation: 

NMOG emissions= NMHC*1.04 

The 1.04 factor was published as part of EPA's Tier 2 regulations. 

4. Combined emission standards. 

The CFV standards for heavy-duty vehicles include a combined NMHC+NOx standard 

expressed in glbhp-hr. To compare to today's standards, not only must the measurement 

units be converted, but the NMHC standard must be converted to NMOG. Also, because 

the Tier 2 standards do not include a combined standard, it is necessary to add the 

chassis-based NMOG standard and the chassis-based NOx standard, after using the 

appropriate g/mi to glbhp-hr conversion factor. 

For example, to compare the 2005-2007 model year heavy-duty vehicle chassis-based 

standards for NMOG (0.28 g/mi) and NOx (0.9 g/mi) to the corresponding CFV engine 

based emission standard for the sum of NMHC + NOx (3.8 glbhp-hr), the following 

conversions were performed: 

Converting 0.28 g/mi NMOG to NMHC: 

0.280 g/mi NMOG/1.04 = 0.27 g/mi NMHC 

Summing the 0.27 g/mi NMHC and 0.9 NOx heavy-duty vehicle chassis standards: 

0.27 g/mi NMHC + 0.9 g/mi NOx = 1.17 g/mi (NMHC + NOx) 

Converting the 3.8 glbhp-hr CFV engine based standard to g/mi units: 

3.8 glbhp-hr (NMHC + NOx)*1.096 = 4.16 g/mi (NMHC + NOx) 

Comparing the current heavy-duty vehicle chassis standard to the CFV engine standard: 

1.17 g/mi < 4.16 g/mi 

2