What Is an Out-of-Service Rate? The Metric Most Brokers Misread

Ask a freight broker what a carrier's out-of-service rate tells them and you'll usually get some version of "it shows how safe their trucks are." That's partially true. But it misses the most useful thing an OOS rate actually reveals, which is not just whether a carrier passes inspections, but whether they take maintenance and driver compliance seriously enough that the problems never show up at the scale in the first place.

A carrier with a 5% vehicle OOS rate and a carrier with a 35% vehicle OOS rate might both have trucks on the road right now. Both have active authority. Both have insurance on file. But one of them is sending equipment out the door that federal inspectors are pulling off the road more than a third of the time. That's not a safety data point. That's a maintenance culture, and it shows up in the OOS rate before it shows up anywhere else.

This guide explains what out-of-service rates actually measure, how to read them correctly, what the national averages are, and how to use OOS data in carrier vetting without making the mistakes that lead to either rejecting good carriers or booking dangerous ones.

What Is an Out-of-Service Rate?

An out-of-service (OOS) rate is the percentage of roadside inspections where a driver or vehicle was found to have violations serious enough that a federal or state inspector ordered them off the road until the problem was corrected.

There are two separate OOS rates for every carrier:

Driver OOS rate measures the percentage of inspections where the driver was placed out of service. Common reasons include an expired or invalid CDL, no valid medical certificate, hours-of-service violations severe enough to be an imminent hazard, and drug or alcohol violations.

Vehicle OOS rate measures the percentage of inspections where the vehicle (truck, trailer, or both) was placed out of service. The most common reasons are brake deficiencies, tire problems, and lighting/electrical failures.

These are calculated separately because they reflect different aspects of a carrier's operation. A carrier can have an excellent driver OOS rate and a terrible vehicle OOS rate, which tells you their drivers are qualified and compliant but their maintenance program is failing. The reverse pattern (clean vehicles, problematic drivers) tells a different story entirely.

The formula is simple:

OOS Rate = (Number of inspections with OOS violations / Total number of inspections) x 100

A carrier with 50 inspections over 24 months and 12 vehicle OOS events has a vehicle OOS rate of 24%.

National Average OOS Rates: The Benchmarks That Matter

Every carrier's OOS rate needs to be compared against something to be meaningful. The national averages, updated annually by FMCSA based on millions of inspections, are the standard benchmark:

National average driver OOS rate: 5.51%

National average vehicle OOS rate: 20.72%

That vehicle number surprises people. One in five trucks inspected nationally gets placed out of service for a mechanical deficiency. That's the baseline. It means a carrier with a 22% vehicle OOS rate is essentially average, not outstanding. And it means a carrier with a 10% vehicle OOS rate is performing meaningfully better than most of the industry.

The driver OOS rate is much lower because driver qualification violations are less common at the roadside. Most drivers have valid CDLs and current medical certificates. The 5.51% average reflects the relatively small number of inspections that catch things like expired med cards, HOS violations severe enough for an OOS order, or disqualified drivers.

Use our OOS rate calculator to check any carrier's rates against these national averages instantly, with color-coded indicators showing whether they're above or below the benchmark.

How OOS Rates Differ From CSA/BASIC Scores

This distinction matters because brokers who confuse the two end up making the wrong calls.

An OOS rate is a straightforward ratio: inspections with OOS violations divided by total inspections. It's an absolute number. A 15% vehicle OOS rate means 15% of inspections resulted in an out-of-service order.

A BASIC score is a percentile ranking that factors in violation severity weighting, time weighting (recent violations count more), and peer group comparison. A 60th percentile Vehicle Maintenance BASIC score means the carrier is performing worse than 60% of similarly sized carriers in that category.

A carrier can have a moderate OOS rate but a high BASIC percentile, or vice versa. Here's why:

The OOS rate only counts violations severe enough for an out-of-service order. A carrier could have dozens of minor violations (inoperative turn signal, cracked windshield, missing mud flap) that never trigger an OOS order but still push their Vehicle Maintenance BASIC score up because those violations carry severity weights in the BASIC calculation.

Conversely, a carrier could have a high OOS rate based on a small number of inspections (say, 2 OOS events out of 6 total inspections = 33% OOS rate) but a moderate BASIC score because the peer group comparison accounts for the small sample size.

Use both. The OOS rate tells you what percentage of inspections resulted in something serious enough to pull the truck or driver off the road. The BASIC score tells you how the carrier's overall violation profile compares to peers. They're complementary signals, not substitutes for each other.

For a full breakdown of how BASIC scoring works, read our complete CSA score guide.

The Six Inspection Levels (And Why They Affect OOS Rates)

Not all roadside inspections are the same. FMCSA defines six levels of inspection, and each one covers different things. Understanding the levels helps you interpret OOS rates more accurately.

Level 1: Full Inspection (North American Standard)

The most comprehensive inspection. Covers the driver's credentials, hours-of-service records, vehicle mechanical condition (under and around the vehicle), and cargo securement. This is the inspection most likely to produce an OOS violation because it examines everything.

Level 2: Walk-Around Driver/Vehicle Inspection

Covers the same driver elements as Level 1 but the vehicle inspection is limited to what can be observed without getting under the truck. No crawling under the vehicle to check brake components. Less likely to catch brake-related issues than a Level 1.

Level 3: Driver-Only Inspection

Only the driver's credentials and HOS records are checked. The vehicle is not inspected at all. OOS violations from Level 3 inspections are exclusively driver-related (expired CDL, no med card, HOS violations).

Level 4: Special Study Inspection

A one-time examination of a specific item, often conducted as part of a research study. Uncommon and generally not significant for vetting purposes.

Level 5: Vehicle-Only Inspection

The vehicle is inspected but the driver is not. These can happen when the driver is not present or when the inspection specifically targets vehicle condition.

Level 6: Enhanced NAS Inspection for Radioactive Materials

Only applies to carriers hauling radioactive shipments. Includes everything in Level 1 plus additional radiological checks.

Why this matters: A carrier whose inspections are mostly Level 3 (driver-only) will have a vehicle OOS rate based on very few actual vehicle inspections, making that number unreliable. A carrier with a high proportion of Level 1 inspections has been subjected to the most thorough scrutiny, and their OOS rate reflects that scrutiny. Check the inspection breakdown with our inspection history tool, which shows the level of each inspection alongside the OOS results.

How to Read OOS Rates During Carrier Vetting

Here's the practical framework for using OOS data in a booking decision.

Step 1: Check the Inspection Count First

An OOS rate is only meaningful if the inspection count behind it is large enough to be statistically significant. A carrier with 3 inspections and 1 OOS event has a 33% OOS rate, but that single data point could easily be an anomaly. A carrier with 80 inspections and a 33% OOS rate has a genuine, documented pattern.

As a rough guide:

• Fewer than 5 inspections: The OOS rate is unreliable. Don't base a booking decision on it.
• 5 to 15 inspections: Directionally useful but not definitive. Look at the specific violations, not just the rate.
• 15 to 50 inspections: Reliable enough to use as a meaningful signal.
• 50+ inspections: Statistically solid. The rate reflects a real pattern.

Our OOS rate calculator flags carriers with fewer than 5 inspections so you know when the data isn't reliable enough to draw conclusions from.

Step 2: Compare to the Right Benchmark

The national averages (5.51% driver, 20.72% vehicle) are the standard benchmark, but fleet size matters. Large carriers tend to have lower vehicle OOS rates than small carriers, partly because they have dedicated maintenance departments and partly because they have more inspections (which smooths out statistical noise).

Approximate vehicle OOS rate benchmarks by fleet size:

• 1 to 10 trucks: 22 to 28% is typical
• 11 to 50 trucks: 18 to 24% is typical
• 51 to 200 trucks: 16 to 22% is typical
• 201 to 1,000 trucks: 14 to 20% is typical
• 1,000+ trucks: 12 to 18% is typical

A 5-truck carrier with a 25% vehicle OOS rate is performing roughly in line with peers. The same 25% rate at a 500-truck carrier would be concerning because fleets that size typically run tighter maintenance programs and should be performing better.

Step 3: Look at the Trend, Not Just the Snapshot

A carrier at 28% vehicle OOS today who was at 40% six months ago is moving in the right direction. A carrier at 18% who was at 10% six months ago is trending the wrong way and may cross into concerning territory soon.

Our OOS rate calculator shows 6-month trend data (improving, stable, or worsening) so you can see the direction, not just the current number.

Step 4: Look at What's Causing the OOS Violations

The OOS rate tells you how often a carrier gets pulled off the road. The inspection history tells you why. And the "why" matters enormously.

A carrier with a high vehicle OOS rate driven primarily by lighting violations (inoperative markers, damaged reflectors) is dealing with a nuisance problem that's easy to fix. A carrier with a high vehicle OOS rate driven by brake failures and tire blowouts has a maintenance program that is genuinely failing at the things that prevent crashes.

The tool automatically detects recurring violation patterns and flags them. If you see "brake violations appear in over 30% of inspections," that's a different conversation than "lighting violations appear in 25% of inspections."

Step 5: Check How Close to FMCSA Intervention

FMCSA doesn't set an explicit OOS rate threshold for intervention, but elevated OOS rates feed into BASIC scores, and BASIC scores do have intervention thresholds (65% for Vehicle Maintenance, 65% for Unsafe Driving, etc.). A carrier whose OOS rate is driving their BASIC scores toward those thresholds is at risk of FMCSA enforcement action.

Our OOS risk meter shows exactly how close each of a carrier's BASIC scores is to the intervention threshold, so you can assess regulatory risk alongside safety risk.

What Causes High OOS Rates (And What Carriers Can Do About It)

Vehicle OOS: The Usual Suspects

The same deficiencies show up over and over in vehicle OOS violations nationally:

Brakes. Out of adjustment, worn components, air system leaks, missing or broken parts. Brake deficiencies are the single largest category of vehicle OOS violations in the US. Carriers who enforce regular brake adjustments and replace components proactively see immediate improvement.

Tires. Tread depth below legal minimum, sidewall damage, flat tires, mismatched duals. Tire violations carry high severity weights and are among the easiest defects to catch during a pre-trip inspection.

Lights and reflectors. Inoperative turn signals, missing reflective tape, damaged headlights or taillights. These violations are common but generally carry lower severity weights than brake or tire issues.

Cargo securement. Insufficient tie-downs, improper blocking, unsecured loads. These violations are more common on flatbed and specialized carriers than on van or reefer operations.

Driver OOS: The Usual Suspects

Hours-of-service violations. Driving beyond the 11-hour limit, violating the 14-hour window, or failing to take the required 30-minute break. With the ELD mandate in full effect, these violations now reflect actual driving-time exceedances rather than logbook paperwork errors. See our HOS rules calculator for a quick reference on current federal limits.

Medical certificate issues. Expired or missing DOT medical certificate. This is an administrative problem with a simple fix (schedule the exam before it expires), but it's one of the most common driver OOS triggers.

CDL issues. Expired CDL, wrong class for the vehicle being operated, missing endorsements. Like med card issues, these are preventable administrative failures.

The Fix: Pre-Trip Inspections That Actually Happen

The majority of vehicle OOS violations are for defects that a genuine pre-trip inspection would catch. Not the kind where a driver checks every box on the DVIR in 30 seconds without leaving the cab. The kind where someone actually walks around the truck, checks the brake stroke, kicks the tires, tests the lights, and looks at the coupling.

Carriers who enforce real pre-trips consistently outperform their peers on vehicle OOS rates. It's not complicated. It's just not optional if you want clean numbers.

OOS Rates and Insurance Premiums

Insurance underwriters look at OOS rates as part of their risk assessment, but they weight them differently depending on the type.

A high vehicle OOS rate suggests deferred maintenance, which correlates with mechanical failure risk. Underwriters see this as a controllable risk factor. If the carrier isn't maintaining equipment, crashes caused by equipment failure are a foreseeable outcome.

A high driver OOS rate suggests either poor driver hiring practices (unqualified drivers) or poor compliance management (drivers running over hours). Underwriters treat this as an indicator of management quality.

In both cases, rates significantly above the national average will increase premiums. The exact impact depends on the underwriter's model, but the relationship is directional: higher OOS rates mean higher insurance costs. Lower OOS rates contribute to lower premiums, especially when combined with clean BASIC scores and a favorable loss history.

Check any carrier's insurance filing status alongside their OOS data for the full picture.

OOS Rates vs. Violation Rates: A Distinction Worth Making

Not every violation results in an out-of-service order. A carrier can receive multiple violations during an inspection without being placed out of service if none of the individual violations meet the OOS criteria.

This means a carrier can have a low OOS rate and a high violation rate. Their trucks aren't getting pulled off the road, but inspectors are consistently finding problems. That pattern suggests the carrier is operating just above the OOS line, which is a different kind of risk signal. The violations are accumulating, pushing BASIC scores up, and one slightly worse inspection could tip them into OOS territory.

The inspection history tool shows both the OOS results and the total violation count for each inspection, so you can see whether a carrier is running clean or just running slightly above the line.

Frequently Asked Questions

What is a good out-of-service rate?

Below the national average is the baseline target: under 5.51% for driver OOS and under 20.72% for vehicle OOS. Carriers performing significantly below these averages (under 3% driver, under 15% vehicle) are running well. Rates more than double the national average are a red flag in any vetting process.

How is an out-of-service rate calculated?

OOS Rate = (Number of inspections with OOS orders / Total number of inspections) x 100. Driver and vehicle OOS rates are calculated separately. The calculation covers the most recent 24 months of inspection data.

Where can I check a carrier's OOS rate?

FMCSA's SMS website at ai.fmcsa.dot.gov/SMS shows OOS data. Our OOS rate calculator shows the same data with national average comparisons, fleet-size benchmarks, and 6-month trend analysis.

Do out-of-service rates affect CSA scores?

Yes. OOS violations feed into BASIC score calculations. An out-of-service violation carries additional weight because it indicates a deficiency serious enough that an inspector ordered the driver or vehicle off the road. High OOS rates are one of the primary drivers of elevated Vehicle Maintenance and Driver Fitness BASIC percentiles.

What happens when a truck is placed out of service?

The driver or vehicle (or both) cannot operate until the cited deficiency is corrected. For vehicle OOS, this typically means the truck must be repaired at the inspection location or towed to a repair facility. The carrier cannot simply drive the truck to a shop. For driver OOS, the driver must go off duty until the disqualifying condition is resolved (e.g., completing required rest, obtaining a valid medical certificate).

How often are OOS rates updated?

FMCSA updates inspection data monthly. The OOS rate reflects a rolling 24-month window, so each month the oldest inspections drop off and the most recent ones are added. This means rates change gradually over time rather than jumping suddenly.

Can a carrier have a 0% OOS rate?

Yes, and many small carriers do, simply because they've had few inspections and none resulted in OOS orders. A 0% rate on 30+ inspections is a genuinely strong signal. A 0% rate on 2 inspections is statistically meaningless.

What is the difference between driver OOS and vehicle OOS?

Driver OOS means the driver was placed out of service for issues like invalid CDL, expired medical certificate, HOS violations, or drug/alcohol violations. Vehicle OOS means the truck or trailer was placed out of service for mechanical deficiencies like brake failures, tire problems, or lighting issues. They are tracked and reported separately because they reflect different aspects of a carrier's operation.

Bottom Line

A carrier's out-of-service rate is one of the most direct safety signals available in carrier vetting. It doesn't rely on peer group comparisons or severity weighting or percentile math. It answers a simple question: when federal inspectors stop this carrier's trucks, how often do they find something bad enough to pull them off the road?

But the number by itself is not enough. You need the inspection count to know if it's reliable. You need the national average to know if it's good or bad. You need the trend to know if it's getting better or worse. And you need the actual violations to know whether the problems are brake failures or broken reflectors.

Check the rate. Check the count. Check the trend. Check the cause. Then make the call.