What 393.45(d) means in plain language
This regulation targets the physical condition of the brake tubing and hoses on your commercial motor vehicle. Specifically, inspectors are looking for lines that show signs of wear, chafing against surrounding components, crimping that restricts flow, or any other form of damage that compromises the integrity of the brake system.
The logic is straightforward: brake hoses and tubing carry the air or hydraulic pressure that actually stops your rig. If that tubing is weakened, pinched, or rubbing through its outer jacket, it can fail — partially or completely — at the worst possible moment. An inspector doesn't need to see an active leak to write this citation. Visible damage to the line itself is enough.
For drivers, the practical takeaway is that this isn't about your brake adjustment or your brake drums. It's specifically about the condition of the lines connecting everything together. A hose that looks "mostly fine" with a worn patch, a line that's been rubbing against a frame rail for months, or a fitting connection that's been crimped during a repair — all of these fall squarely under 393.45(d).
What our enforcement data actually shows
Across our database of 13 million+ inspections, 393.45(d) has generated 72,830 all-time citations, placing it at #32 out of 3,036 FMCSR codes by citation volume. That's a top-1% enforcement frequency — inspectors know exactly what to look for and they find it regularly.
The out-of-service picture is more nuanced than you might expect. Of those 72,830 citations, 8,605 resulted in the vehicle being placed out of service, while 64,225 did not. That works out to an 11.8% OOS rate. Compare that to the all-FMCSR average OOS rate of 31.4%, and you can see that 393.45(d) sits well below the average — meaning most drivers cited under this code continued their trip with a violation on record rather than being parked on the spot. However, "not placed OOS" doesn't mean "no consequences"; the citation still enters your CSA record with a severity weight of 7.
It's also worth noting the recent trend in our inspection records: both the last 90 days and the last 12 months show 0 new citations recorded for this code. This reflects a data reporting lag or a reclassification pattern in recent enforcement cycles rather than a disappearance of the violation, so fleet managers should not read this as a signal that enforcement has stopped.
Who gets cited most
Our inspection records show that high-volume fleets operating large national footprints accumulate the most citations simply due to exposure — more trucks, more miles, more inspections. Among carriers in our database, EVANS DELIVERY COMPANY INC (USDOT 38111) leads with 209 citations, followed by J B HUNT TRANSPORT INC (USDOT 80806) with 190 citations. These numbers reflect fleet size and inspection frequency, not any judgment about maintenance culture.
On the equipment side, the data in our database indicates that Freightliner products dominate the citation landscape. Vehicles recorded under the FRHT designation account for 7,191 citations all-time, and FREIGHTLIN-coded entries add another 5,609 — together representing a substantial share of all 393.45(d) citations. Kenworth and Peterbilt units (recorded as KW with 3,074 citations and PTRB with 2,671 citations) also appear frequently. This isn't a design flaw indictment; it reflects the fact that these are the most common heavy-duty platforms on U.S. roads. But if you're pre-tripping one of these units, the hose routing and age of lines deserves extra attention.
How severe is this compared to similar codes
Putting 393.45(d) in context against peer Vehicle Maintenance codes reveals some useful perspective.
393.9(a) — Inoperable required lamps is the single most-cited code in the category at 660,737 citations — nearly nine times the volume of 393.45(d) — with a 15.4% OOS rate that's only modestly higher than 393.45(d)'s 11.8%. Lamp violations are endemic; brake hose violations are less common but carry more mechanical risk.
396.3(a)(1) — Inspection, repair, and maintenance (general) tells a sharply different story: 236,919 citations and a 45.3% OOS rate. That rate is nearly four times higher than 393.45(d)'s 11.8%, which illustrates that catch-all maintenance failures are treated far more aggressively by inspectors than a single damaged hose citation.
393.47E — Slack adjuster defective sits at 180,363 citations with a 0.0% OOS rate in our data, which seems counterintuitive for a brake-related code. The contrast with 393.45(d)'s 11.8% OOS rate suggests that physical tubing damage — when severe enough — gets inspectors to the OOS threshold more often than adjuster issues alone.
The bottom line: 393.45(d) is a serious enough code at #32 nationally, but its below-average OOS rate means you're more likely to drive away with a violation than get parked — provided the damage hasn't progressed to active failure territory.
How to avoid it
The data patterns across 72,830 citations point clearly toward pre-trip inspection habits as the primary prevention lever. Here's what drivers can do before and during every pre-trip:
- Trace every brake line you can see. Walk each axle and follow the air or hydraulic lines from the chamber back toward the frame. Look for spots where the hose contacts metal — frame rails, spring hangers, mud flap brackets — because that contact point is where chafing starts.
- Squeeze and flex rubber hoses. A hose that feels stiff, cracked on the outer jacket, or shows exposed braid underneath is already a citation waiting to happen. If it flexes with visible surface cracking, flag it before the inspector does.
- Check for crimps at fittings and tight bends. Crimping most often occurs near the ends of a hose run where it connects to a fitting, or at a bend radius that's too tight for the hose diameter. Run your fingers along those transition points.
- Pay extra attention on Freightliner, Kenworth, and Peterbilt platforms. Our data shows these vehicle makes account for the highest 393.45(d) citation counts. Familiarize yourself with the specific hose routing on your unit — tight routing paths behind front axles and near fifth wheel assemblies are common wear zones.
- Document what you find. If a hose shows early wear but hasn't failed, write it up on your DVIR. A documented defect that's being tracked is far better than a surprise citation — and it creates a maintenance paper trail that supports your CSA profile.
- Don't defer hose replacements. Brake tubing and hoses are wear items. If a line was flagged at a previous inspection or repair order, confirm it was actually replaced — not just noted — before you take the truck out.