MUTCD W10-5 - Low ground clearance railroad crossing warning sign. From: Manual on Uniform Traffic Control Devices for Streets and Highways - 2003 Edition.

This file is in the public domain because it comes from the Manual on Uniform Traffic Control Devices, sign number W10-5, which states specifically on page I-1 that: 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.