Why the Loose Cutpoints During Program Start-up?
The emission standards used in the I/M240 test are expressed in terms of grams per mile rather than as a percentage or in parts per million, as in the case with steady-state tests. Different standards are set for each model year and reflect the technology that was in effect at the time of manufacture. The standards are typically two to three times higher than new vehicle certification standards for the model year. EPA recommends that standards be phased-in over two test cycles. The standards in the first cycle, referred to as phase-in standards, are set much looser than the new vehicle standards. The purpose of setting the standards loosely at first are many-fold: About 40-45% of vehicles currently operating need emission-related repairs. Failing all of these vehicles in the first cycle would overwhelm the repair industry and make the program much more expensive, since more testing capacity would be needed to conduct retests. The phase-in standards will fail only the dirtiest vehicles
