This report adresses the relationship between short test emission results and emissions as measured on the 'complete' or certification test (hydrocarbons and carbon monoxide) for 1981 and later model year light duty vehicles and light duty trucks. As provided in section 207(b) of the Clean air Act, EPA must establish an Emissions Performance Warranty if a short test can be developed which is (1) available (2) in accordance with good engineering practice and (3) reasonably capable of being correlated with the Federal Test Procedure (FTP). The purpose of this report is to evaluate the correlation of idle and loaded short test emissions to results which will be obtained on the certification test for 1981 model year and later passenger cars and light trucks. This report addresses the issue of correlation for 1981 and later model year vehicles, Data from 1975-77 model federal cars was examined. Three short tests are recommended: idle, two speed idle and two mode loaded. These short tests are associated standards give approximately the same error of commission rate as the FTP (comparing single test results to average emission levels) while identifying a substantial part of the excess emissions.