[Code of Federal Regulations]
[Title 40, Volume 29]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR610.42]

[Page 1006]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 610_FUEL ECONOMY RETROFIT DEVICES--Table of Contents
 
                Subpart D_General Vehicle Test Procedures
 
Sec. 610.42  Fuel economy measurement.

    (a) Fuel consumption will be measured by:
    (1) The carbon balance method, or
    (2) Gravimetric or volumetric methods. In the gravimetric and 
volumetric methods, fuel consumption is determined by weighing the fuel 
source before and after a test, or by measuring the volume of fuel 
consumed during a test. Since the distance traveled during the tests is 
known, the fuel economy, in miles per gallon, can be calculated. 
Gravimetric and volumetric methods require the use of special test 
equipment in addition to the emissions measuring equipment.
    (b) The carbon balance procedure for measuring fuel consumption 
relates the carbon products in the exhaust to the amount of fuel burned 
during the test. This method will be the one used to measure fuel 
economy unless track or road tests are employed.
    (c) Three values of fuel economy will be reported: for city driving 
('75 FTP), for highway driving (HFET), and the combined city/highway 
value calculated according to this equation:
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