[Code of Federal Regulations] [Title 49, Volume 5] [Revised as of October 1, 2005] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR393.81] [Page 425] TITLE 49--TRANSPORTATION DEPARTMENT OF TRANSPORTATION PART 393_PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION--Table of Contents Subpart G_Miscellaneous Parts and Accessories Sec. 393.81 Horn. Every bus, truck, truck-tractor, and every driven motor vehicle in drive away-towaway operations shall be equipped with a horn and actuating elements which shall be in such condition as to give an adequate and reliable warning signal.