If you could only look at one number before tendering freight to a carrier, it should be their vehicle out-of-service rate.

CSA scores get the most attention. Crash history gets the most fear. But out-of-service rates tell you something neither of those can: what a federal inspector found when they actually looked at the truck.

What Out-of-Service Means

When a commercial motor vehicle is inspected at a roadside checkpoint or weigh station, the inspector examines the vehicle, the driver, or both. If they find violations severe enough to be an imminent hazard — brakes that don't work, tires with exposed cords, a driver without a valid medical certificate — the vehicle or driver is placed out of service.

Out of service means the truck doesn't move until the problem is fixed. It's the inspector's way of saying "this vehicle or driver is too dangerous to continue operating right now."

The out-of-service rate is the percentage of inspections that result in an OOS order. There are three types:

Vehicle OOS rate: Percentage of vehicle inspections resulting in a vehicle being placed OOS
Driver OOS rate: Percentage of driver inspections resulting in a driver being placed OOS
Hazmat OOS rate: Percentage of hazmat inspections resulting in OOS (only for hazmat carriers)

The National Averages

As of the most recent FMCSA data:

Category	National Average
Vehicle OOS Rate	~20.7%
Driver OOS Rate	~5.5%
Hazmat OOS Rate	~4.5%

Read that first number again. On average, roughly one in five commercial vehicles inspected on US roads is found to have defects serious enough to be pulled from service. That's the national average. Some carriers are significantly worse.

Why OOS Rates Matter More Than You Think

OOS rates are a leading indicator, not a lagging one. Here's why they matter:

They measure actual condition, not paperwork. CSA scores are calculated from violation records, which can be influenced by inspection frequency, geographic location, and data entry timing. OOS rates reflect what an inspector found when they put hands on the equipment.

High vehicle OOS rates predict crashes. Multiple FMCSA studies have found a strong correlation between vehicle OOS rates and crash rates. A carrier that can't keep its trucks in safe operating condition is a carrier whose trucks are more likely to fail on the road.

They reveal maintenance culture. A carrier with a 35% vehicle OOS rate doesn't have a few bad trucks — they have a systemic maintenance problem. Brake defects, tire failures, and lighting violations at that rate suggest that the shop isn't catching problems before trucks hit the road.

They're hard to game. You can't talk your way out of a brake measurement that doesn't meet spec. You can't argue that a bald tire is actually fine. OOS determinations are based on physical measurements and observable conditions, making them harder to dispute than some other violation categories.

What the Numbers Look Like in Practice

Here's a rough guide to interpreting vehicle OOS rates:

Under 15%: Below national average. Indicates above-average maintenance practices.
15-21%: Around national average. Typical for the industry.
21-30%: Above average. Worth investigating further.
30-40%: Significantly above average. Indicates structural maintenance problems.
Above 40%: Severe. Almost half the fleet fails when inspected. Major red flag.

For driver OOS rates, the scale is tighter because the national average is lower:

Under 4%: Good.
4-6%: Average.
6-10%: Above average. Check driver fitness and HOS scores too.
Above 10%: Concerning. Suggests driver qualification or compliance issues.

How Shippers Should Use This

When evaluating a carrier, pull their OOS rates and compare them against national averages. If their vehicle OOS rate is double the national average, that tells you something meaningful about how their fleet is maintained — regardless of what their CSA percentiles show.

Combine OOS rates with the Vehicle Maintenance BASIC score and crash history for the most complete picture of fleet condition. A carrier can have a reasonable-looking CSA percentile due to limited inspection data while still running equipment that fails at a high rate when inspected.

The data is public. It's on every carrier profile in the FMCSA SAFER System, and it's displayed on every carrier profile on CarrierWatch. It takes 30 seconds to check. There's no reason not to.