PASSING THE TEST - HUMAN-BEHAVIOR AND CALIFORNIA SMOG CHECK PROGRAM

We have analyzed data obtained from more than 11,000 vehicles inspecte d in California's random roadside surveys to assess the real-world cha racteristics of the in-use motor vehicle fleet and to test the effecti veness of California's inspection and maintenance (I/M) program. The l ow-idle emissions data from these surveys show that 10 percent of the fleet are responsible for about 60 percent of the exhaust hydrocarbons and also that 10 percent of the fleet (not necessarily the same vehic les) are responsible for about 60 percent of the carbon monoxide emiss ions. We also show that high emitters appear among all model years, an d not just among old vehicles, as previously assumed. Old vehicles, on average, have higher idle emissions than new vehicles, but they contr ibute relatively little to the total idle emissions because there are so few on the road. We compare roadside survey results at I/M and non- I/M locations in California, and observe identical tampering and overa ll failure rates at the two types of locations. We also show that moto rists are taking steps to ''pass the test,'' and that the high-emittin g vehicles' idle-emissions performance and tampering rates in the road side surveys are unaffected by the Smog Check test. These results impl y that success in California's Smog Check program in reducing emission s will require consideration of human behavior and the attendant negat ive incentives inherent in the program as historically conceived. EPA' s national tampering surveys also show little difference in tampering rates among areas with decentralized, centralized and no I/M programs. We therefore propose that an I/M 'shootout'' be conducted to evaluate candidate programs for the next generation of I/M programs in the Uni ted States.