Vehicle Pre-Trip Inspection

A pre-trip inspection is the check a commercial driver makes before driving a truck or bus. It is a federal duty that belongs to the driver, and it is a graded part of the CDL skills test. It is not a shop inspection. A technician's multi-point check or a state safety inspection on a car is different work under different rules. This inspection is you, the driver, deciding whether this vehicle is safe to take on the road today.

The inspection catches problems while they are cheap: a loose lug nut in the yard instead of a lost wheel on the highway. It also protects you. When a defect is found at the roadside, your name is on the inspection report along with the carrier's.

What You Will Be Able to Do

• Explain what federal rules require of a driver before and after a trip.
• Follow the seven-step inspection in the same order every time.
• Judge tires, wheels, brakes, steering and emergency equipment against real limits.
• Decide when a defect means the vehicle stays parked.
• Complete a Driver Vehicle Inspection Report (DVIR) and review the last one.

What the Rules Require

The rule applies before you drive, so that means at the start of each day and each time you take over a vehicle. A swap at a terminal counts. Someone else's inspection does not replace yours.

There is no federal minimum time. A careful inspection of a tractor-trailer commonly takes 15 to 30 minutes. Log that time as on duty, not driving. It is paid work in the eyes of the rules, even if your employer pays by the mile.

A defect found at the roadside can bring a violation on the driver's and carrier's records. A serious defect can bring an out-of-service order, which means the vehicle cannot move until the problem is fixed. Driving in violation of an out-of-service order can disqualify a CDL holder for at least 180 days on a first offense.

Before You Start

Park on level ground if you can. Set the parking brake, and chock the wheels if you will be working around the engine or under the vehicle. Wear gloves and sturdy boots. Carry a flashlight, a tire gauge and a tread depth gauge. Use three points of contact every time you climb on or off the vehicle: two hands and a foot, or two feet and a hand.

Warning: Never open a radiator cap on a hot engine. The system is under pressure, and the coolant can spray out and cause serious burns. Check the level at the see-through reservoir.

The Seven-Step Inspection

State CDL manuals teach this order. Use it every time so that nothing is skipped.

Step 1: Vehicle Overview

Walk up to the vehicle and look at it as a whole before you touch it.

1. Is it leaning to one side? That can mean a flat tire, a broken spring or a shifted load.
2. Look underneath for fresh puddles of oil, coolant, fuel or grease.
3. Look around it for low wires, limbs, people or anything else you could hit.
4. Read the last DVIR. If it listed defects, confirm the carrier certified the repair or that repair was not needed.

Step 2: Engine Compartment

With the engine off and the parking brake set, tilt the cab or open the hood.

• Fluids: Check engine oil, coolant and power steering fluid levels, and washer fluid. Look for leaks.
• Belts: Look for cracks and fraying, and check they are tight on the pulleys.
• Hoses: Squeeze gently and look for soft spots, cracks, bulges and leaks.
• Wiring and battery: No loose, frayed or bare wires. Terminals clean and tight, battery secure.
• Steering gear and linkage: No leaks or missing fasteners. No bent, cracked or loose parts.
• Air compressor and water pump: Secure and not leaking.

Step 3: Start the Engine and Inspect the Cab

Get in, make sure the parking brake is on and the transmission is in neutral or park, and start the engine.

• Gauges: Oil pressure should rise within seconds. Air pressure should build. Coolant temperature should climb slowly. The charging gauge should show the alternator working. Check fuel and diesel exhaust fluid levels.
• Warning lights: They should come on at key-on and go out, including the ABS lamp.
• Controls: Test the horn, wipers, washers, heater, defroster and all light switches.
• Seat belt: Latches and holds.
• Mirrors and windshield: Clean, secure, not cracked in a way that blocks your view.
• Steering play: With the engine running on power steering, turn the wheel gently until the front wheels just begin to move. CDL manuals treat more than 10 degrees of play, about 2 inches at the rim of a 20-inch wheel, as a problem. Use that figure for your inspection and your test. The federal roadside limit in 49 CFR 393.209 is looser for that same wheel, at 2 1/2 inches for manual steering and 5 1/4 inches for power steering, but you should not wait for it.

Emergency equipment must be in the cab and ready to use:

• A charged fire extinguisher, rated 5 B:C or more, or 10 B:C or more on a vehicle hauling placarded hazardous materials.
• Three bidirectional reflective warning triangles. Six fusees are also allowed in many cases, but not on vehicles carrying explosives or flammable loads.

Federal rules stopped requiring spare fuses on April 20, 2026. State CDL manuals can lag behind, so if your manual still lists them, learn that answer for your test.

Paperwork to have with you includes your CDL, registration, proof of insurance, any permits, and the ELD or logs. Your employer may add to the list.

Step 4: Turn Off the Engine and Check Lights

Shut the engine off, take the key with you, and turn on the headlights and four-way flashers. Walk to the front. Check low beams, high beams and both front flashers.

Step 5: Walk-Around Inspection

Go around the vehicle in one direction. On each side, work from front to rear.

Tires:

Wheels and rims: All lug nuts present and tight. Rust streaks running outward from a lug nut mean the nut is loose, so do not drive until it has been properly tightened. Look for cracked or bent rims and welding repairs. Check hub seals for leaks and oil level through the hub window if there is one.

Brakes you can see:

• Brake chambers and hoses are not cracked, leaking or loose.
• Drums and rotors are not cracked, and linings are not thin or soaked in oil.
• Slack adjusters are not broken or missing. With the wheels chocked and the parking brake released, a manual slack adjuster should not move more than about 1 inch where the pushrod attaches when you pull it by hand.
• After a short drive, touch near each drum carefully. One drum much hotter than the others means that brake is dragging, and one much cooler may not be working.

Suspension and steering: Look for cracked or broken spring leaves, shifted or missing parts, leaking shocks, and damaged air bags. Check spring hangers, U-bolts and torque rods. Check that the drag link and tie rod are not bent or loose.

Frame and drivetrain: No cracks or bends in the frame or cross members. Driveshaft not bent, U-joints not worn. Fuel tanks secure, caps tight, no leaks.

Exhaust: Look for leaks, loose clamps, broken hangers, damaged heat shields, and any contact with fuel lines, wiring or air lines. Soot around a joint is a sign of a leak.

Coupling on a combination vehicle: Confirm the fifth wheel is mounted securely, the locking jaws are closed around the kingpin shank, the lever is locked with the safety latch in place, and there is no gap between the fifth wheel and the trailer apron. Air and electrical lines must be connected, undamaged and not dragging. The landing gear must be fully raised with the crank handle secured.

Rear of the vehicle and cargo: Check lights, reflectors, mud flaps, the rear impact guard and the plate. Doors must latch. Cargo must be secured, and any tarp must be tied down.

Step 6: Check Signal Lights

Get back in, turn off the flashers, and turn on the right turn signal. Get out and check it front and rear, then repeat for the left. Have someone press the brake pedal or use a reflection to confirm the brake lights.

Step 7: Start the Engine and Check the Brakes

On a hydraulic brake vehicle, pump the pedal three times, then hold it for five seconds. It should not sink. On a vehicle with air brakes, run the checks below. Finish every vehicle with a parking brake test and a service brake test: pull forward slowly, about 5 mph, press the brake firmly, and notice any pull to one side or a delay in stopping.

Air brake checks with the numbers used by state CDL manuals:

Your state's manual has the final say on the numbers it tests.

Reporting Defects

A DVIR is your written report on the condition of the vehicle. Federal rules require a report at the end of each day's work on each vehicle you drove, when you found a defect or someone reported one to you. If there were no defects, the federal rule does not require a report, but many carriers still have you complete one every day. Follow your carrier's policy.

The end-of-day check that feeds this report is called a post-trip inspection. It records what you noticed while driving, along with anything you find on a last walk-around.

The report must cover at least the service brakes and trailer brake connections, parking brake, steering, lights and reflectors, tires, horn, wipers, mirrors, coupling devices, wheels and rims, and emergency equipment.

1. Write down each defect in plain, specific words. "Left rear marker light out" tells a mechanic what to do, and "light bad" does not.
2. Sign the report.
3. The carrier must repair the defect or certify that repair is not needed before the vehicle runs again.
4. The next driver reviews the report and signs it, confirming the repair was certified.
5. The carrier keeps the report and certifications for three months.

Reports can be electronic. Many carriers use an app or the ELD, and federal rules say so directly.

When to Stay Parked

Some defects can wait for a shop visit. Others mean the vehicle does not move. Do not drive with any of these until a repair is made and recorded:

• Brakes that do not work or an air leak over the limit
• A low air warning that does not work
• Steering parts that are loose, broken or missing
• A flat tire, audible leak, or exposed ply or belts
• Loose or missing wheel fasteners, or a cracked rim
• A coupling that is not locked or has a gap
• Fuel or exhaust leaks into the cab or near hot parts
• Lights required for the conditions that do not work

Record the defect on the DVIR, tell the carrier, and wait for the repair. A federal rule, 49 CFR 390.6, bars a carrier or shipper from pressuring you to break safety rules, and federal law protects you from retaliation for refusing to drive an unsafe vehicle.

Common Mistakes

Check Your Understanding

You take over a tractor at a relay point. The last driver says it ran fine. Do you need to inspect it?

Yes. You must be satisfied the vehicle is safe before you drive it. Review the last DVIR if it listed defects, then do your own inspection.

During the walk-around you see a brown streak running out from one lug nut. What does it mean and what do you do?

It points to a loose nut. Do not move the vehicle. Report it and have the wheel properly tightened before you drive.

The last DVIR says "right mud flap torn", and there is no repair note. What do you do?

Do not sign off. The carrier must certify the repair, or that repair is not needed, before you take the vehicle. Ask the carrier to complete it.

You drove all day and noticed nothing wrong. Your carrier has no daily DVIR policy. Does federal law require a report?

No. A report is required when a defect is found or reported. If your carrier requires one every day, you must still complete it.

You fan the brakes during your air check and the warning buzzer does not sound until 40 psi. What now?

That fails the test. The warning should come on before about 60 psi. Keep the vehicle parked, record the defect, and report it.

Key Takeaways

• A pre-trip inspection is the driver's federal duty. It is not a shop inspection, and nobody else can do it for you.
• Use the same seven steps every time so that nothing gets skipped.
• Steer tires need at least 4/32 inch of tread, and other tires need at least 2/32 inch.
• Report defects on a DVIR. The carrier must certify the repair before the vehicle runs again, and it keeps the report for three months.
• If the brakes, steering, tires, wheels or coupling are unsafe, the vehicle stays parked.