§FMCSR.com
Current textSource: eCFR

§ 393.19 Hazard warning signals.

Current wording, in the annual edition revised as of Oct. 1, 2005.

eCFR (current) ↗
What changedOct. 1, 1996 wording → Oct. 1, 2005 wording (current)+28 added−100 removedHide

(a)The Everyhazard bus,warning truck,signal oroperating truckunit tractoron shalleach becommercial equippedmotor withvehicle a signaling system that in addition to signaling turning movements shall haveoperate aindependently switch or combination of switches that will cause the twoignition frontor turnequivalent signalsswitch, and thewhen twoactivated, rearcause all turn signals to flash simultaneously as a vehicular traffic hazard warning as required by § 392393.2211 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 § 392.22(a).
[5370 FR 4939748046, DecAug. 715, 19882005]

49 CFR § 393.19 — Hazard warning signals.. Text current through October 22, 2026. This wording effective October 1, 2005 to present. Source: eCFR (current), https://www.ecfr.gov/current/title-49/section-393.19. Retrieved from FMCSR.com, https://fmcsr.com/reg/393.19, on October 26, 2026. Unofficial compilation; verify against the official source.

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]

Amendment history

2 distinct wordings on file since Oct. 1, 1996
  1. Oct. 1, 2005 → presentannual editions 2005–2016diff vs. previousviewing
    [70 FR 48046, Aug. 15, 2005]
  2. Oct. 1, 1996 → Oct. 1, 2005annual editions 1996–2004
    [53 FR 49397, Dec. 7, 1988]

A new entry appears whenever the regulatory words change between government snapshots. Day-precise from the eCFR (2017 onward); before that, one snapshot per annual CFR edition (revised as of October 1). Bracketed citations are the Federal Register history printed with the section. Set a case date in the header to read any earlier wording.