Because motor vehicles contribute substantially to air pollution, the Environmental Protection Agency (EPA), in November 1992, issued a rule requiring 83 of the more seriously polluted areas in 23 states to implement more stringent programs--called enhanced inspection and maintenance (I&M) programs--for testing and reducing vehicles' emissions. This rule established credits for the reductions in emissions anticipated from implementing the various elements of an I&M program. It also allowed states to vary these elements, including the type of testing network to be used in periodically testing vehicles' emissions, provided the overall reductions anticipated from implementing a state's I&M program would be at least as great as the reductions achievable from implementing EPA's model, or benchmark, program. Testing networks, which consist of authorized facilities throughout an area, may be test-only, test-and-repair, or hybrid (using both types of facilities). However, EPA's data, collected before November 1992, indicated that test-and-repair networks were less effective in controlling emissions than test-only networks. Consequently, EPA's rule provided that the number of credits assigned to test-and-repair networks would be decreased by 50%, while test-only networks would receive full credit. Some states and other interested parties questioned the adequacy of EPA's supporting data for this 50% discount and maintained that it amounted, in practice, to an inflexible requirement for using test-only networks. In light of the concerns raised by the 50% discount, the General Accounting Office (GAO) was asked to provide (1) the results of any audits, surveys, or studies performed since November 1992 that have a bearing on this discount and (2) the status of EPA's efforts to provide states with more flexibility in designing I&M programs. Briefly, GAO's findings are as follows: Of the few relevant studies that have been performed since November 1992, no clear consensus on the relative effectiveness of test-and-repair and test-only programs was found. EPA has taken several actions to provide states with more flexibility in designing and implementing enhanced I&M programs. These are discussed in this report. In November 1995 the Congress enacted legislation eliminating any automatic discounts based on the type of testing network and giving states 18 months to collect new data demonstrating the effectiveness of their I&M programs, including their testing networks. On December 12, 1995, EPA issued guidance to its regions suggesting innovative program features that states may use to improve the effectiveness of their test-and-repair programs.

  • Record URL:
  • Supplemental Notes:
    • Report to the Chairman, Subcommittee on Oversight and Investigations, Committee on Commerce, House of Representatives.
  • Corporate Authors:

    U.S. General Accounting Office

    441 G Street, NW
    Washington, DC  United States  20548
  • Publication Date: 1996-3


  • English

Media Info

  • Features: Appendices; Tables;
  • Pagination: 29 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00722649
  • Record Type: Publication
  • Report/Paper Numbers: GAO/RCED-96-63
  • Files: TRIS
  • Created Date: Jun 26 1996 12:00AM