English: Sign D9-18a as it appeared in editions of the MUTCD and Standard Highway Signs and Markings from as early as 2000 until 2023, when it was revised. [1][2]
Any traffic control device design or application provision contained in this Manual shall be considered to be in the public domain. Traffic control devices contained in this Manual shall not be protected by a patent, trademark, or copyright, except for the Interstate Shield and any other items owned by FHWA.