23 CFR § 1235.4 - Removable windshield placards.
(a) The State system shall provide for the issuance and periodic renewal of a removable windshield placard, upon the application of a person with a disability which limits or impairs the ability to walk. The State system shall require that the issuing authority shall, upon request, issue one additional placard to applicants who do not have special license plates.
(b) The initial application shall be accompanied by the certification of a licensed physician that the applicant meets the § 1235.2(b) definition of persons with disabilities which limit or impair the ability to walk.
(c) The State system shall require that the removable windshield placard is displayed in such a manner that it may be viewed from the front and rear of the vehicle by hanging it from the front windshield rearview mirror of a vehicle utilizing a parking space reserved for persons with disabilities. When there is no rearview mirror, the placard shall be displayed on the dashboard.