USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Federal Exhaust Emissions Certification Standards for Newly Manufactured Gasoline- and Diesel-Powered Heavy-Duty Trucks

(Grams per brake horsepower-hour)

Embedded Dataset Excel:

Dataset Excel:

table_04_37q207.xlsx (14.93 KB)


Tables 4-32a and 4-32b are identical for heavy-duty diesel engines.


KEY: CO = carbon monoxide; HC = hydrocarbon; NOx = nitrogen oxides; NMHC = nonmethane hydrocarbons.

a Smoke opacity is expressed in percentage for acceleration, lugging, and peak modes (acceleration/lugging/peak).  Lugging is when a vehicle is carrying a load.

b Gross vehicle weight rating (GVWR) is the maximum design loaded weight.

c Several testing procedures have been used during the course of exhaust emissions control.  A steady-state 9-mode test procedure (13-mode for diesel) was used for 1970-83 standards. For 1984, either the steady-state tests or the U.S. Environmental Protection Agency (EPA) transient test procedure could be used.  For diesels, the EPA transient test was required from 1985 to the present.  For gasoline-powered vehicles, either the EPA or the Motor Vehicle Manufacturers Association (MVMA) transient test procedure could be used during 1985-86, and the MVMA procedure was required thereafter. 

d Emissions standards apply to the useful life of the vehicle.  Useful life was 5 years/50,000 miles through 1983 and became 8 years/110,000 miles beginning in model year 1985. 1984 was a transitional year in which vehicles could meet the older standard (and test procedure) or the newer one.  Useful life requirement for gasoline-powered trucks meeting NOx standards for 1998 and after is 10 years/110,000 miles.  Starting in 2004, the useful life will be 10 years/110,000 miles.  The useful life requirements for heavy-duty diesel truck standards are more complex and vary by vehicle weight, pollutant, test procedure, and year.  Consult the U.S. Code of Federal Regulations for further information. 

e No standard set.

f Although emissions standards for HC and CO were in effect for these years, they were not measured in grams per brake horsepower-hour and are, therefore, incompatible with this table. 

g Vehicles can meet a NMHC +  NOx standard of 2.5 g/bhp-h, given they meet a NMHC standard of no more than 0.5 g/bhp-h.


40 CFR 86, Electronic Code of Federal Regulations, internet site at as of Oct. 9, 2001. 

U.S. Environmental Protection Agency, Office of Transportation and Air Quality, personnal communication, Oct. 2001.