Thus, the type of testing network is only one of many variables that can influence an I&M program’s effectiveness. Officials from the other nine states required to implement enhanced I&M programs told us that while their states have conducted some audits and/or tampering surveys since 1992, these efforts were not designed to assess the relative effectiveness of different types of I&M networks and therefore could not be used, according to the officials, to compare test-only to test-and-repair programs. For example, in contrast to the Georgia study discussed earlier, which indicated that Atlanta’s I&M hybrid program was more effective in reducing emissions than EPA’s 50-percent discount would indicate, a California study found little difference in the effectiveness of a test-only program and a test-and-repair program and observed that both were less effective than EPA’s model program. Also in February 1995, EPA established credits for the states that require repairs to be performed by trained, certified mechanics, and for less costly testing systems. Additionally, in September 1995 EPA revised its 1992 rule to allow states to meet a new, less stringent performance standard as long as the states could still meet their overall targets for reducing emissions. They further suggested that we point out early in the report that recent legislation has eliminated any automatic discounts of test-and-repair networks. We found that only 2 (California and Georgia) of the 23 states that are required to implement an enhanced I&M program have developed data since November 1992, when EPA issued its enhanced I&M rule decreasing the number of credits assigned to test-and-repair networks by 50 percent.According to state air program officials, this 50-percent discount has not been more widely addressed for several reasons, which are discussed in this appendix. The principal researcher said this study was not designed to evaluate the relative effectiveness of test-and-repair and test-only I&M networks and therefore did not directly address the 50-percent discount. A recorded menu will provide information on how to obtain these lists.
Why GAO Did This Study

Pursuant to a congressional request, GAO provided information on the 50-percent penalty, also called a discount, that states suffer under the Environmental Protection Agency's (EPA) Clean Air Act enforcement for operating vehicle emissions inspection and maintenance (I&M) test-and-repair networks instead of test networks.

What GAO Found

GAO found that: (1) EPA issued the 50-percent discount rule after it found that test-and-repair networks were less effective in controlling motor vehicle emissions; (2) since issuing the rule, EPA has not conducted any studies to obtain new data on the effectiveness of test-and-repair networks; (3) 14 of the 23 states required to implement enhanced I&M programs have not conducted studies on the 50-percent discount, mostly because they implemented, or intended to implement, test-only programs; (4) the other 9 states did not conduct studies to assess the relative effectiveness of the two kinds of I&M networks; (5) California studied relative effectiveness and concluded that there was little difference between test-and-repair networks and test-only networks; (6) Georgia is conducting a study, and the preliminary findings lead Georgia to believe that it should suffer only a 35- to 45-percent discount for its hybrid I&M program; and (7) Congress enacted legislation to eliminate automatic discounts based on the type of testing network and allow states 18 months to study their I&M programs' effectiveness. GAO also found that EPA has allowed the states great flexibility in implementing enhanced I&M programs by: (1) providing I&M system models; (2) establishing credits for test-only networks, for states that require that only certified mechanics perform repairs, and for less costly testing systems; (3) relaxing performance standards for states that can still meet their overall targets for reducing emissions.