Today's action revises the Motor Vehicle Inspection/ Maintenance (I/M) program requirements to provide additional flexibility to state I/M programs, both in response to the I/M provisions of the National Highway System Designation Act of 1995 (NHSDA), and in compliance with the Clean Air Act requirement that EPA's guidance for such programs be "from time to time revised." Today's action: Modifies the current enhanced I/M performance standard modeling requirements to reflect delays caused by the NHSDA, and to provide states greater flexibility in how they meet the performance standard; removes the I/M rule provision establishing the decentralized, test-and-repair credit discount; revises certain test procedure, standard, and equipment requirements to better accommodate alternative test types and program designs; streamlines the data collection, analysis, and reporting requirements to make them consistent with various alternative test and program types; makes minor revisions to the inspector training requirements also to accommodate various alternative test and program types; revises the requirements for consumer protection and improving repair effectiveness to limit the current requirement to provide diagnostic information to those programs and test types capable of producing such information, reliably and practically; and expands the options for complying with the on-road testing requirement to accommodate more recent variations, such as clean screening and non-tailpipe based, roadside tests.