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.

Site Notification

Site Notification

 Find the latest Coronavirus-related transportation statistics on the BTS COVID-19 landing page.

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:



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.