DOT Out-of-Service Criteria Explained for Truck Drivers

What “out of service” actually means

In a roadside inspection, the officer checks the vehicle against the North American Standard Out-of-Service Criteria, published by the Commercial Vehicle Safety Alliance (CVSA). If the vehicle or driver violates those criteria, it’s placed out of service and can’t operate until the problem is corrected.

Not every violation is an out-of-service violation. An inspector can write up a defect as a regular violation — which still counts against the carrier’s safety record — without parking the truck. The out-of-service criteria mark where a defect is serious enough that the truck shouldn’t move.

CVSA revises the criteria regularly, with new editions typically taking effect April 1. This guide gives common examples in plain language; inspectors use the current official criteria.

Brakes

Brakes are consistently one of the top reasons trucks go out of service. Brake conditions that can trigger an out-of-service order include:

Too many defective brakes. When 20 percent or more of the service brakes on a vehicle or combination are defective — including brakes out of adjustment — the vehicle is out of service.
Steer axle brakes that are inoperative or have certain defects.
Air leaks, such as an audible leak at a brake chamber, or air loss beyond allowed limits.
Damaged parts — broken or missing components, cracked drums, and linings soaked in oil or grease or worn past limits.
Air supply problems that affect the system’s ability to build and hold pressure.
Tractor protection and breakaway systems that don’t work as required.

Pushrod stroke past the adjustment limit for the chamber size is a very common finding. Depending on how far past the limit it is, an out-of-adjustment brake counts as a full or partial defective brake toward the 20 percent rule. Trucks that run the East Tennessee grades wear brakes faster, so check adjustment often.

Tires and wheels

Steer tires with less than 2/32 inch of tread in any two adjacent major grooves.
Other tires with less than 1/32 inch of tread in two adjacent major grooves at multiple locations.
Flat tires, or tires with an audible leak.
Exposed belt or ply material through the tread or sidewall.
Tires touching another tire or part of the vehicle.
Wheels and rims with cracks, or loose, missing, or broken lug nuts and studs beyond allowed limits.

The federal maintenance rules set higher tread minimums — 4/32 inch on steer tires and 2/32 inch on other tires — so a tire can earn a violation well before it hits the out-of-service level.

Lights and reflectors

Lighting problems are among the most common vehicle violations overall. For out-of-service purposes, the criteria focus on the lights that matter most for being seen and signaling — for example, required stop lamps or rear turn signals that don’t work on the last vehicle in the combination, or required lamps out at night or in poor visibility.

Winter road brine is a big cause of lighting failures around here. It corrodes seven-way plugs, pigtails, and sockets. Walk around the truck with the lights and flashers on during every pre-trip.

Suspension, frame, and coupling

Leaf springs with a quarter or more of the leaves in any spring assembly broken, or a broken main leaf.
Air suspension that’s deflated or has damaged air springs.
Torque rods, U-bolts, and spring hangers that are broken, missing, or loose enough to let the axle shift.
Frame cracks and broken frame members beyond allowed limits.
Fifth wheel and coupling defects, including locking jaws that don’t close properly and mounting problems.

Other common categories

Cargo securement that doesn’t meet requirements or lets cargo shift.
Fuel leaks — dripping fuel from tanks, lines, or fittings.
Exhaust leaks that can put fumes into the cab, or exhaust parts where they could burn wiring, fuel lines, or cargo.
Steering — too much steering wheel lash, and loose or damaged steering parts.
Driver issues, separate from vehicle defects — hours of service, license, and medical certificate problems.

How to stay in service

Do a real pre-trip. Walk around with the lights and flashers on, check tires and wheels, listen for air leaks, and look at brake chambers and slack adjusters.
Fix defects when you find them, not the next time the truck happens to be at a shop.
Keep annual inspections current and use them to catch wear early. See mobile DOT inspections.
Stay on top of preventive maintenance. See fleet PM service.

Trucks running I-40 and I-75 through Knoxville pass the Knox County scale house near mile marker 372. If a truck is placed out of service there or anywhere else, a mobile mechanic can often correct the defects on the spot. Keep the inspection report — it lists exactly what has to be fixed.

General information only. This guide is written for drivers and dispatchers working around Knoxville and East Tennessee. Rules change and every truck is different — follow your carrier's procedures, current FMCSA regulations, and the directions of the Tennessee Highway Patrol or other officers on scene.

Out-of-Service Criteria: What Gets a Truck Parked