The Effect of Restorative Maintenance on the Relationship Between Short Test and Federal Test Procedure Emission Test Results

The Restorative Maintenance Program conducted by the Environment Protection Agency in late 1976 and early 1977 provides short test and Federal Test Procedure data on a large fleet of relatively new consumer owned automobiles. The program included testing of 300 vehicles in Chicago, Detroit and Washington, D.C. The vehicles that indicated a need for maintenance were repaired and retested by the FTP and the five short tests being considered by the agency for the Federal warranty regulations.

These data are examined by conventional regression and correlation methods, contingency table analysis and maintenance effectiveness criteria.

The conclusions of the study indicate that while the mathematical correlation coefficients are quite low for most of the tests, all five tests are effective in identifying vehicles in need of maintenance and significant hydrocarbon and carbon monoxide emissions reductions can be achieved at relative low vehicle failure rates. The transient mode tests are also effective in identifying oxides of nitrogen reduction potentials.