What 393.19 means in plain language
FMCSR 393.19 targets a specific piece of safety equipment: your hazard warning flashers. The regulation requires that the system allowing all turn signals to flash simultaneously — commonly called your four-ways — must be fully operational at all times. If an inspector activates your hazard switch and any part of the system fails to respond correctly, you can be cited.
This is not a vague or interpretive regulation. Either the flashers work when the switch is thrown, or they don't. A single inoperative corner, a switch that fires intermittently, or a system that activates but only flashes on one side of the vehicle — all of these can put you in violation.
The practical reason behind the rule is straightforward: hazard flashers are a critical warning tool when a CMV is stopped or slowed unexpectedly on a roadway. A truck that can't signal danger to approaching traffic creates a real collision risk, which is why inspectors test this system during Level I and Level II roadside inspections.
What our enforcement data actually shows
Across our database of 13 million+ inspections, 393.19 has generated 30,339 all-time citations, placing it at #96 out of 3,036 FMCSR codes by citation volume. That puts it in the top 4% of all codes for enforcement frequency — inspectors write this one regularly.
In the last 12 months alone, our inspection records show 9,983 citations for 393.19. Drilling down further, 2,128 citations were issued in just the last 90 days, confirming this is an actively enforced violation right now, not a legacy code that inspectors rarely apply.
Here's the good news for your situation: the out-of-service rate for 393.19 is 0.2% across all 30,339 inspections — meaning only 65 vehicles were placed out of service out of 30,274 that were not. The all-FMCSR average OOS rate is 31.4%, so 393.19 sits dramatically below that benchmark. Being cited does not typically mean your truck gets parked.
That said, the citation still carries a CSA severity weight of 3 and falls under BASIC 5 (Vehicle Maintenance). It goes on your record and your carrier's record. It may not stop your trip, but it affects your Inspection Selection System score and contributes to your carrier's BASIC percentile.
Looking at the monthly trend over the last 12 months, citations have run consistently between 810 and 947 per month from May 2025 through March 2026, with a brief dip to 319 in April 2025. Enforcement has not softened — if anything, the data in our database indicates activity has been steady and elevated.
Who gets cited most
The top three states by citation count in the last 180 days are Texas (3,454 citations), Georgia (142 citations), and Arizona (114 citations). Texas is not just the leader — it dominates the count in a way that reflects the heavy cross-border commercial traffic through that corridor. The OOS rate in Texas over that period was 0.2% (8 out of 3,454), consistent with the national average for this code. Georgia and Arizona both logged 0.0% OOS rates in the same window, meaning no trucks were parked in those states for this violation during that period.
New Mexico (97 citations), Pennsylvania (83), and New York (69) round out the next tier, each with 0.0% OOS rates over the same window. The geographic spread — from the Southwest border to the Northeast — confirms this isn't a regional enforcement push. Inspectors across the country are checking hazard systems.
Our data shows fleets such as RS TRANSFER SA DE CV (USDOT 1156825) with 111 all-time citations and AUTOTRANSPORTES VARELA DAVILA SA DE CV (USDOT 1716824) with 100 all-time citations appearing at the top of the carrier list. The concentration of citations among cross-border carriers operating in high-volume Texas corridors is consistent with the state-level data.
By vehicle make, Freightliner (FRHT) accounts for 6,276 all-time citations — the highest of any manufacturer — followed by Kenworth (KW) at 3,182 and utility trailers (UTIL) at 2,152. Given how many Freightliners and Kenworths are on the road, this largely reflects fleet composition, but it's a useful reminder that no manufacturer's wiring is immune to this failure mode.
How severe is this compared to similar codes
Within the Vehicle Maintenance category, 393.19 is a relatively low-severity code compared to its peers. Consider a few comparisons drawn from our inspection records:
- 393.9(a) — Inoperable required lamps has 660,737 all-time citations and a 15.4% OOS rate. That's a code inspectors write far more often and that parks trucks at a rate roughly 77 times higher than 393.19.
- 396.3(a)(1) — Inspection, repair, and maintenance (general) has 236,919 citations and a 45.3% OOS rate — meaning nearly half of those citations result in the driver being parked. That's a stark contrast to 393.19's 0.2% rate.
- 393.11 — Lighting devices and reflectors has 179,734 citations and a 1.8% OOS rate, still nine times higher than what our database shows for 393.19.
In short, 393.19 is a high-frequency code with a low consequence for immediate operations, but the CSA weight still accumulates over time. Repeated citations — even at severity weight 3 — compound in the BASIC system.
How to avoid it
The co-occurring violation data from our database is telling. In the last 90 days, 393.19 shared inspections most frequently with 393.9TS (inoperative turn signal, 1,395 shared inspections) and 393.9 (inoperable required lamp, 921 shared inspections). This pattern tells a clear story: when hazard flashers fail, it's almost always part of a broader electrical or lighting system issue. Inspectors who find one lamp problem tend to find more.
Here are concrete pre-trip and in-cab actions to keep 393.19 off your record:
- Test your four-way flashers at every pre-trip, not just your turn signals. Turn signals can work independently even when the hazard system switch or relay has failed. These are separate circuits on most trucks. Activate the hazard switch, walk completely around the vehicle, and confirm all four corners are flashing in sync.
- Check for dim or slow-flashing lights. A flasher that blinks too slowly often indicates a failing bulb or corroded socket elsewhere in the circuit. Inspectors can cite a system that "doesn't function properly" even if it technically turns on.
- Inspect the hazard switch itself. On high-mileage Freightliners and Kenworths — the top two cited makes in our records — the hazard switch is a known wear point. If the button feels loose, sticky, or requires multiple presses, flag it for maintenance before your next inspection.
- Address turn signal issues immediately. With 1,395 inspections showing both 393.19 and 393.9TS together, a bad turn signal bulb or relay is a leading indicator that your hazard system is next. Fix turn signals during your daily inspection, not during a roadside stop.
- Log and repair windshield and lighting defects together. 393.78 (windshield condition) and 393.11 (lighting devices) co-occurred with 393.19 in 450 and 255 inspections respectively in the last 90 days. Inspectors doing a thorough inspection will pull the thread on all lighting and visibility defects at once. A clean truck with working lights across the board is your best defense.