On October 22, 1996, the final rule on Motor Vehicle Emissions Federal Test Procedure Revisions was published in the United States Federal Register

Federal Register

The Federal Register , abbreviated FR, or sometimes Fed. Reg.) is the official journal of the federal government of the United States that contains most routine publications and public notices of government agencies...

. This rule revises the tailpipe emissions portion of the Federal Test Procedure (FTP) for Light-duty vehicles (LDVs) and light-duty trucks (LDTs).
FTP is shown in http://www.epa.gov/oms/emisslab/methods/ftpdds.gif