[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2002] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR393.19] [Page 1057] TITLE 49--TRANSPORTATION CHAPTER III--FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 393--PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION--Table of Contents Subpart B--Lighting Devices, Reflectors, and Electrical Equipment Sec. 393.19 Requirements for turn signaling systems. (a) Every bus, truck, or truck tractor shall be equipped with a signaling system that in addition to signaling turning movements shall have a switch or combination of switches that will cause the two front turn signals and the two rear turn signals to flash simultaneously as a vehicular traffic hazard warning as required by Sec. 392.22 with the ignition on or off. (b) Every semitrailer and full trailer shall be equipped so as to have the two rear turn signals to flash simultaneously with the two front turn signals of the towing vehicle as a vehicular traffic hazard warning as required by Sec. 392.22(a). [53 FR 49397, Dec. 7, 1988]