That 0% OOS Rate Looks Perfect. Now Ask How Many Inspections Built It.

A broker called me last fall to walk through a carrier he was excited about. Clean SAFER profile, zero crashes, 0% out-of-service rate. "This is exactly the kind of carrier I want to build a relationship with," he said. I asked him how many inspections built that 0%. He had to go back and look. Three. Over four months. Authority opened in July.

Three roadside inspections is not a track record. It's barely a sample. A 0% OOS rate on three inspections tells you almost nothing about whether this carrier maintains its equipment — you're reading a verdict from a case that hasn't really had a chance to proceed yet. That broker wasn't careless. He was reading a number that looked meaningful because FMCSA presents it as meaningful. The problem is that a rate without volume is noise, and in carrier vetting, the OOS rate is one of those figures that looks precise and often isn't.

What the OOS Rate Actually Is

FMCSA's out-of-service rate is a simple ratio: inspections that ended with an OOS designation divided by total inspections, expressed as a percentage. An inspection ends with an OOS order when a roadside compliance officer finds violations serious enough that the vehicle or driver can't continue operating — failed brakes, a driver over hours, a cracked frame rail, a broken steering component.

49 CFR Part 396 governs vehicle inspection and maintenance for motor carriers. § 396.3 requires carriers to inspect, repair, and maintain every vehicle under their control in safe operating condition. § 396.17 establishes the periodic inspection requirement — at minimum once every 12 months, verified by a qualified inspector. A roadside OOS violation is typically a failure of something § 396.3 required the carrier to catch and fix before the truck left the yard.

At load-tender time, the so-what is this: a high vehicle OOS rate is evidence that the carrier isn't maintaining its equipment. A high driver OOS rate tells you it's putting drivers behind the wheel who aren't legal to operate — hours-of-service violations, license issues, log falsifications. But neither observation means anything if the sample size is too thin for the rate to have converged on reality.

Think about it statistically. A carrier with 3 vehicle inspections has a sample from which any rate is equally plausible — 0% is just as random as 67% at that sample size. A carrier with 250 inspections has a rate that's been stress-tested enough to reflect something about the company's actual maintenance culture. The math is the same whether FMCSA highlights the rate in red or presents it clean. The weight you should assign it is not.

The Inspection Count Problem

FMCSA shows you the OOS rate prominently. It doesn't surface the inspection count that produced it in any equally prominent way. You have to go find it — in the SAFER company snapshot, in the inspections section, which shows total driver inspections and total vehicle inspections over the last 24 months alongside how many ended in OOS designations. Most brokers copy down the rate and move on without counting the denominator.

Here's the heuristic I use. Take the total vehicle inspection count over 24 months and think about it in proportion to the carrier's authority age and fleet size. A carrier with 40 months of authority and 10 power units should have seen something like 20 to 40 vehicle inspections in 24 months if they're actively moving freight in the U.S. freight lanes. Fewer than that means they're running a limited operation, operating regionally with low exposure to weigh stations, or they haven't been around long enough to accumulate a real sample.

When the vehicle inspection count is below 5, I treat the OOS rate as statistical noise — it's a single coin flip expressed as a percentage. Below 10, I take it seriously but discount it heavily. Above 25, I start reading it as a real signal. Above 50, the rate is telling me something true about how this carrier maintains its fleet, and I should listen.

How Authority Age and OOS Rate Combine

The inspection count problem is directly tied to authority age, because a new carrier simply hasn't been on the road long enough to accumulate a meaningful sample. But the relationship between these two variables is more complicated than "newer = less reliable data." The direction of the signal depends on which combination you're looking at.

Young authority, low OOS rate, thin inspection count: noise. Don't use it to confirm the carrier is safe. You don't have the data yet. Vet everything else harder — crash history if any exists, the SAFER company snapshot officer names, insurance filing history in L&I, the MCS-150 filing dates.

Young authority, elevated OOS rate, even thin inspection count: this is actually meaningful. A carrier that gets pulled 5 times in 7 months and hits OOS on 2 of them has a 40% vehicle OOS rate. That's alarming even at a small sample, because the rate had to be really bad to stand out at a denominator that small. Low sample size cuts against false positives here, not against false negatives.

Old authority, low OOS rate, high inspection count: the profile you want. Been around long enough to get pulled often, consistently clean. This is evidence of a maintenance culture, not a lucky run.

Old authority, high OOS rate, high inspection count: the worst combination. This carrier has been doing it wrong for years and has the inspection history to prove it. A 16% vehicle OOS rate on 280 inspections over six years isn't a bad-luck story. That's how this company operates.

The scenario I see brokers miss most often is the fourth one. They see a stable OOS rate somewhere around industry average and call it acceptable without asking whether it's been stable because the carrier is consistently mediocre or consistently improving. The 24-month rate FMCSA shows is an average. It flattens trend.

A Scenario

MC-1247893 / DOT-3567102. Authority opened March 2023 — about three and a half years of tenure. Fourteen power units on the SAFER snapshot, eleven drivers. Vehicle OOS rate: 12.8% on 94 inspections. Driver OOS rate: 5.2% on 79 inspections.

A broker pulling this cold might see 12.8% vehicle OOS and compare it to the national vehicle OOS average — which runs around 19-21% depending on the quarter. Below average. Looks fine. Move on.

But here's what that broker missed. Ninety-four vehicle inspections over 42 months with 14 power units works out to roughly 1.6 inspections per truck per year. That's on the low end for a carrier actively moving general freight in the Midwest, where weigh station pull-in rates are higher than the national average. The low inspection frequency is itself a flag worth questioning — it may mean the carrier is avoiding certain routes, which some carriers do deliberately to limit their inspection exposure.

More important: if you pull the last-24-month data from DOTScreener's carrier file versus the prior period, you see the vehicle OOS rate was 9.4% in the first 18 months of operation and has climbed to 15.6% in the most recent 12 months. The fleet is deteriorating. The static 12.8% is a blended average that obscures the direction.

The static rate passed. The trend fails. You'd never know without comparing periods.

What Changes When You Screen for This

Continuous carrier monitoring matters here specifically because OOS rates aren't static. A carrier that was genuinely clean at onboarding 14 months ago can develop a vehicle OOS problem as equipment ages, maintenance gets deferred, or driver turnover disrupts the inspection culture on pre-trips.

DOTScreener's Continuous Monitoring re-runs carrier checks against FMCSA data sources — SAFER, L&I insurance filing history, authority status — and flags material changes between screens. When a carrier's OOS rate shifts in a direction you'd care about, that surface in the carrier's file. The Carrier Selection Record that re-files with each re-screen means the due-diligence timestamp advances with the load, not just at initial approval.

That matters post-Montgomery because the question in discovery isn't whether you vetted the carrier at onboarding. It's whether you knew what was happening to their safety record in the months after. A carrier selection document from 14 months ago doesn't answer "why did you tender this carrier 47 more times while their vehicle OOS rate climbed from 9% to 19%?" A Continuous Monitoring file does.

The inspection count variable is part of what makes per-load vetting non-trivial. It's not enough to run the carrier and check the OOS rate. You need to assess whether the rate is statistically meaningful given the sample behind it, and whether it's stable or trending in a direction that matters.

How I Document This

For every carrier I approve on a new lane or use more than five times in a rolling 90 days, the file I keep includes:

The SAFER screenshot with the OOS rate and the inspection count both visible — not just the rate. The authority grant date so the months of tenure are calculable by anyone who opens the file later. An explicit note if the inspection count is below 10 vehicle inspections, noting that the rate is treated as insufficient sample, and what other signals I'm relying on instead — usually authority age, officer history, insurance continuity from L&I, crash record quality. For repeat carriers: the re-screen date and result, with inspection counts at each re-screen so a trend is visible across the file.

If I'm passing on a carrier because of a high OOS rate, I note both the rate and the sample behind it. "Vehicle OOS 28% on 6 inspections, authority 5 months, insufficient sample for reliable inference, declined on combination of OOS trend and sub-6-month authority" is more defensible than "OOS 28%, declined." It shows I understood what the number meant and what it didn't. That distinction is the whole ballgame under deposition.

The broker who called me about that pristine carrier with the 0% rate on three inspections ended up using the carrier anyway. The load delivered without incident, which happens — most loads do. But three inspections later, the same carrier popped a 33% vehicle OOS rate when a compliance officer found brake adjustment issues on both drive axles. That failure showed up in the carrier's SAFER record. If a load had gone wrong between the second and third inspection, the broker's vetting file would have shown he knew the OOS rate was built on three data points and chose to proceed. That's a conversation he didn't want to have.

The number means something. Understanding what built it is the difference between screening and reading.

— Mason Lavallet

Founder, DOTScreener.com