Amends the Clean Air Act to direct the Administrator of the Environmental Protection Agency to revise and republish in the Federal Register guidance for State motor vehicle inspection and maintenance programs to establish additional requirements for States that contract out emissions testing and inspection services to a private vendor. Requires such programs to use a voucher system under which a vehicle owner may use a voucher (equal to the reimbursement rate per vehicle under the State's contract with a vendor) to: (1) have a vehicle inspected by the State's chosen vendor; or (2) defray part of the cost of an inspection by a licensed private concern.