49 C.F.R. § 393.19 Hazard warning signals.
Title 49 - Transportation
The hazard warning signal operating unit on each commercial motor vehicle shall operate independently of the ignition or equivalent switch, and when activated, cause all turn signals required by §393.11 to flash simultaneously. [70 FR 48046, Aug. 15, 2005]
Title 49: Transportation
PART 393—PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION
Subpart B—Lamps, Reflective Devices, and Electrical Wiring
§ 393.19 Hazard warning signals.
