This rule changes a provision of the federal vehicle inspection and maintenance (I/M) rules relating to motorist compliance enforcement mechanisms for pre-existing programs. The current rule limits the use of pre-existing enforcement mechanisms, other than denial of vehicle registration, to those geographic areas previously subject to the I/M program. This rule change allows states to employ such effective pre-existing enforcement mechanisms as sticker enforcement in any area in the state adopting an I/M program. This amendment is consistent with the relevant requirements of the Clean Air Act. These changes will not result in any change in health and environmental benefits.