CDL Vehicle Inspection

Pre-trip, en-route and post-trip inspections: what to check and what defects put a commercial vehicle out of service.

134 practice questions with answers. These rules are the same in every state.

CDL Vehicle Inspection quiz

Answer at your own pace. After each question you see the correct answer and why, and at the end a review of what you missed.

Quick quiz: 10 random questions on cdl vehicle inspection; pass with 8 correct.

CDL Vehicle Inspection questions with answers

Under federal safety rules, what must the driver of a commercial vehicle do before starting a trip?
1. Be satisfied that the vehicle is in safe operating condition
2. Have a supervisor record the odometer reading on the trip sheet
3. Let the engine idle for at least thirty minutes
4. Obtain a certified mechanic signature on the load manifest before leaving
Show answer

Answer A: Be satisfied that the vehicle is in safe operating condition

The driver is responsible for inspecting the vehicle and must be satisfied it is in safe operating condition before the trip begins.
What is the first step of the standard seven-step vehicle inspection?
1. Checking that the turn signals, brake lights and marker lamps all work correctly
2. Starting the engine and testing the brake system
3. A general overview of the vehicle, including the last inspection report
4. Draining the water and oil that have collected in the air tanks
Show answer

Answer C: A general overview of the vehicle, including the last inspection report

The routine opens with a walk-up overview of the vehicle and a review of the previous inspection report so known defects are addressed first.
Before raising the hood to inspect the engine compartment, what should you do?
1. Disconnect both battery cables and tag the master switch before opening the hood
2. Shut off the engine, set the parking brake and chock the wheels if needed
3. Raise the trailer landing gear
4. Drain the fuel filter and top up the coolant reservoir
Show answer

Answer B: Shut off the engine, set the parking brake and chock the wheels if needed

The engine compartment is inspected with the engine off and the vehicle secured so nothing can move or turn while your hands are inside.
What is the minimum tread depth required in every major groove of a steering axle tire?
1. 1/32 inch
2. 2/32 inch
3. 3/32 inch
4. 4/32 inch
Show answer

Answer D: 4/32 inch

Federal rules set a higher tread minimum for front steering tires than for other positions because a steering tire failure is far harder to control.

Source: ecfr.gov
What is the minimum tread depth for tires in positions other than the steering axle?
1. 2/32 inch
2. 4/32 inch
3. 5/32 inch
4. 6/32 inch
Show answer

Answer A: 2/32 inch

Drive and trailer tires must keep at least 2/32 inch of tread in a major groove, measured away from tie bars and fillets.

Source: ecfr.gov
Where are regrooved, recapped or retreaded tires not allowed on a truck or truck tractor?
1. On any axle of a full trailer or a converter dolly
2. On the rear drive axle of a loaded truck tractor
3. On the front steering wheels
4. On the spare tire only
Show answer

Answer C: On the front steering wheels

Regrooved and retreaded tires are prohibited on the front wheels of a truck or truck tractor because a steering tire blowout is extremely difficult to manage.

Source: ecfr.gov
How much free play in the steering wheel is enough to make a vehicle hard to steer and should be reported?
1. Any play at all is an automatic defect
2. More than 10 degrees, roughly 2 inches of movement at the rim of a 20 inch wheel
3. More than 2 degrees of movement
4. More than 45 degrees of movement
Show answer

Answer B: More than 10 degrees, roughly 2 inches of movement at the rim of a 20 inch wheel

Excess play means steering input is lost before the wheels respond, and more than about 10 degrees is treated as a defect.

Source: oregon.gov
Which set of emergency equipment must be carried on a commercial motor vehicle?
1. A tow chain, an approved first aid kit, a mounted spare tire and a hydraulic jack rated for the loaded axle weight
2. Wheel chocks, a shovel, a reflective vest and a set of tire chains
3. A fire extinguisher, a flashlight and jumper cables
4. A fire extinguisher, spare electrical fuses unless the vehicle has circuit breakers, and warning devices
Show answer

Answer D: A fire extinguisher, spare electrical fuses unless the vehicle has circuit breakers, and warning devices

The required kit is a properly charged and rated fire extinguisher, spare fuses when the vehicle uses them, and warning devices for a stopped vehicle.
Which combination of warning devices meets the requirement for a stopped commercial vehicle?
1. Three reflective triangles, or six fusees, or three liquid burning flares
2. Two reflective triangles or four fusees
3. One reflective triangle and one flare
4. Four reflective triangles or two liquid burning flares
Show answer

Answer A: Three reflective triangles, or six fusees, or three liquid burning flares

A vehicle may carry three bidirectional reflective triangles, six fusees or three liquid burning flares as its warning devices.
On a two lane road carrying traffic in both directions, where do the three warning devices go?
1. All three within 10 feet of the vehicle
2. About 100, 200 and 300 feet behind the vehicle
3. About 10 feet from the vehicle on the traffic side, 100 feet behind and 100 feet ahead
4. About 10, 50 and 100 feet behind the vehicle only
Show answer

Answer C: About 10 feet from the vehicle on the traffic side, 100 feet behind and 100 feet ahead

Traffic can approach from either direction, so one device goes close to the vehicle and one is placed about 100 feet away in each direction.

Source: ecfr.gov
On a one way street or a divided highway, where are the warning devices placed?
1. About 50, 150 and 250 feet behind the vehicle
2. About 10 feet, 100 feet and 200 feet back toward the approaching traffic
3. About 10 feet and 100 feet in each direction
4. A single device about 200 feet behind the vehicle
Show answer

Answer B: About 10 feet, 100 feet and 200 feet back toward the approaching traffic

When traffic can only come from one side, all three devices are spread out behind the vehicle to give approaching drivers a longer warning.

Source: ecfr.gov
How soon must warning devices be placed after a commercial vehicle stops on the traveled part or the shoulder of a highway?
1. Within one hour
2. Only if the stop will last more than two hours
3. Within thirty minutes
4. As soon as possible and in any case within 10 minutes
Show answer

Answer D: As soon as possible and in any case within 10 minutes

The hazard warning flashers go on immediately and the warning devices must be in place as soon as possible, never later than 10 minutes after stopping.

Source: ecfr.gov
Your vehicle is stopped just past a hill or curve that hides it from approaching traffic. How should the warning devices be adjusted?
1. Move the rearmost device farther back, up to 500 feet, so drivers are warned before the obstruction
2. Place all three devices right next to the vehicle
3. Leave the warning devices stowed in the vehicle and rely on the hazard flashers and the clearance lamps
4. Set all three devices on the opposite shoulder of the road facing the traffic
Show answer

Answer A: Move the rearmost device farther back, up to 500 feet, so drivers are warned before the obstruction

When a hill or curve blocks the view, the farthest device is moved back beyond the obstruction so approaching drivers see the warning in time.
What must a written driver vehicle inspection report cover at the end of the day?
1. The route taken, the fuel purchased and the miles driven in each state crossed during the day
2. The weather conditions during the trip and any delay they caused
3. Any defect or deficiency that would affect safety or could cause a mechanical breakdown
4. The names of everyone who rode in the vehicle
Show answer

Answer C: Any defect or deficiency that would affect safety or could cause a mechanical breakdown

The report identifies the vehicle and lists defects that affect safe operation or could lead to a breakdown, so they are repaired before the next trip.

Source: ecfr.gov
What should you do with the previous driver vehicle inspection report before starting your trip?
1. File it with the shipper before the trailer is loaded
2. Review it and confirm that listed defects were certified as repaired or as not needing repair
3. Transcribe the contents of the previous report into your log for the day and sign both documents
4. Discard it once the vehicle has been loaded
Show answer

Answer B: Review it and confirm that listed defects were certified as repaired or as not needing repair

Reviewing the last report and the carrier certification tells you whether reported defects have been corrected before you take the vehicle out.

Source: ecfr.gov
Study tip. Rule out the options you know are wrong first. Two plausible answers are easier to choose between than four.
Which items belong to the in-cab part of the inspection?
1. Brake drum thickness, lining condition and slack adjuster travel at each wheel
2. Tire pressure, wheel lug nut torque and rim condition at every position
3. Cargo securement on the trailer deck
4. Gauges, controls, mirrors, windshield, wipers, horn, heater and defroster
Show answer

Answer D: Gauges, controls, mirrors, windshield, wipers, horn, heater and defroster

The in-cab step checks the instruments and controls the driver depends on, along with mirrors, glass, wipers, horn and the heater and defroster.
How are the headlights, marker lights and turn signals checked during the seven-step inspection?
1. The engine is shut off, the parking brake is set, the lights are switched on and then checked from outside the vehicle
2. They are checked only before a trip that runs after dark
3. A helper watches them from the shoulder while the vehicle rolls slowly forward
4. They are checked from the driver seat using the dash indicators alone, since every exterior lamp reports back to the panel
Show answer

Answer A: The engine is shut off, the parking brake is set, the lights are switched on and then checked from outside the vehicle

The lights are switched on with the vehicle secured, then the driver walks around and confirms each lamp actually works and is clean.
Which wheel or rim condition must be treated as a defect during the walkaround?
1. Light surface rust on the rim face where the paint has worn away
2. Brake dust collected on the wheel after a long descent
3. Cracks, illegal welded repairs, or missing and loose lug nuts
4. A wheel that has recently been repainted
Show answer

Answer C: Cracks, illegal welded repairs, or missing and loose lug nuts

Cracked or welded rims and missing or loose fasteners can let a wheel separate from the vehicle and must be corrected before driving.
What are you looking for when you check the hubs and wheel seals during the walkaround?
1. The date the wheels were last balanced and the mileage run since then
2. Leaking oil or grease, which can also contaminate the brake linings
3. Matching tire brands and tread patterns on the same axle
4. The amount of tread left on the spare tire
Show answer

Answer B: Leaking oil or grease, which can also contaminate the brake linings

A leaking hub seal starves the bearing of lubricant and the escaping oil or grease can soak the brake linings and cut braking power.
Which of these is a suspension defect you must look for during the walkaround?
1. A film of road dust settled on the shock absorber bodies and the spring hangers behind them
2. Dried mud collected on the frame rails above the rear suspension
3. A trailer parked on a slight slope
4. Cracked or broken spring leaves, loose or broken U-bolts, or leaking air suspension bags
Show answer

Answer D: Cracked or broken spring leaves, loose or broken U-bolts, or leaking air suspension bags

Broken springs, failed U-bolts and leaking air bags let the axle shift or the body drop, which can make the vehicle impossible to control.
Which step of the seven-step inspection method comes immediately after checking the engine compartment?
1. Turn off the engine and check the lights all around the vehicle
2. Do the walkaround inspection of the outside of the vehicle
3. Check the signal lights
4. Start the engine and inspect the inside of the cab
Show answer

Answer D: Start the engine and inspect the inside of the cab

Once the hood is closed the driver moves to the driver seat, starts the engine and checks gauges, controls and warning devices before going any further.

Source: oregon.gov
What does the driver check in the final step of the seven-step inspection?
1. Hydraulic brake leaks where those brakes are fitted, then the parking brake and the service brakes
2. The tread depth in every major groove of every tire on the vehicle, and the condition of the mounted spare
3. The shipping papers and the bill of lading
4. The previous driver vehicle inspection report and the repair certification on it
Show answer

Answer A: Hydraulic brake leaks where those brakes are fitted, then the parking brake and the service brakes

The last step is done with the engine started: test for hydraulic leaks on vehicles with hydraulic brakes, then prove that the parking brake holds and that the service brakes stop the vehicle.

Source: oregon.gov
During the vehicle overview, what should the driver look for on the ground under the vehicle?
1. Chalk marks left by the loading crew
2. Fresh puddles of oil, coolant, grease or fuel
3. The manufacturer plate showing the weight rating
4. The tire brands stamped on the sidewalls
Show answer

Answer B: Fresh puddles of oil, coolant, grease or fuel

New stains on the ground are the earliest sign of a leak, so the overview includes a look underneath before anything is opened or started.
What are you looking for when you check the drive belts in the engine compartment?
1. That every belt is lightly coated with grease so it runs quietly
2. That the belts match the color of the hoses
3. That each belt is snug and free of cracks, frays or heavy wear
4. That the belts are loose enough to slip a little under a heavy load
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Answer C: That each belt is snug and free of cracks, frays or heavy wear

A loose or cracked belt can break and stop the fan, the water pump or the alternator, which leads quickly to overheating or a dead electrical system.
Under the federal air brake standard, the low air pressure warning must come on before reservoir pressure drops below what level?
1. Before pressure falls below 60 psi
2. Before pressure falls below 20 psi
3. Before pressure falls below 10 psi
4. Only after the spring brakes have applied
Show answer

Answer A: Before pressure falls below 60 psi

Federal Motor Vehicle Safety Standard 121 requires the warning to operate while service reservoir pressure is still above 60 psi, which leaves enough air to bring the vehicle to a normal stop.

Source: ecfr.gov
What is the driver looking for when the exhaust system is inspected?
1. An exhaust temperature gauge reading of zero once the engine has warmed up to operating temperature
2. Loose, broken or missing pipes, brackets or clamps, and signs that exhaust is leaking
3. A stack that has been polished
4. Insulation wrapped around the muffler and the exhaust stack
Show answer

Answer B: Loose, broken or missing pipes, brackets or clamps, and signs that exhaust is leaking

A loose or leaking exhaust system can send carbon monoxide into the cab and can put hot gas against parts that will burn.
Which steering system findings count as defects during the inspection?
1. Wear marks on the steering wheel cover and on the turn signal stalk
2. A horn button that needs a firm push
3. Bent, loose or broken column parts, arms, drag links or tie rods, and missing nuts, bolts or cotter keys
4. A steering wheel that feels heavier whenever the vehicle is carrying a full load on the front steering axle
Show answer

Answer C: Bent, loose or broken column parts, arms, drag links or tie rods, and missing nuts, bolts or cotter keys

Every joint and fastener between the steering wheel and the tires carries the driver commands, so looseness or a missing retainer can end in a complete loss of steering.
What makes a brake hose or air line a defect during the walkaround?
1. It is longer than the trailer
2. It is painted a different color from the others in the same bundle
3. It is routed inside the frame rail instead of along the outside
4. It is cracked, worn, kinked, or rubbing against another part
Show answer

Answer D: It is cracked, worn, kinked, or rubbing against another part

A chafed or cracked line can burst under pressure and take the braking on that circuit with it, so damage and rubbing points must be corrected.
Federal rules require a power unit that is not carrying placarded hazardous materials to have a fire extinguisher with which minimum rating?
1. One rated 5 B:C or more, or two rated 4 B:C or more each
2. One rated 1 A or more
3. One rated 10 B:C or more
4. Any size at all, as long as it is inside the cab
Show answer

Answer A: One rated 5 B:C or more, or two rated 4 B:C or more each

The minimum is a single unit rated 5 B:C or more, or two units of at least 4 B:C each, which is enough to attack a fuel or electrical fire.

Source: ecfr.gov
What extinguisher rating is required on a vehicle carrying hazardous materials in amounts that need placards?
1. 2 B:C or more
2. 10 B:C or more
3. 4 B:C or more
4. 5 B:C or more
Show answer

Answer B: 10 B:C or more

Placarded loads carry a much higher fire risk, so the required extinguisher rating rises to at least 10 B:C.

Source: ecfr.gov
Federal rules forbid operating a commercial vehicle in which condition?
1. Loaded to less than half of its rated capacity on any axle
2. With a trailer that was coupled by another driver earlier that day
3. In a condition likely to cause a crash or a breakdown
4. With more than one driver listed on the paperwork
Show answer

Answer C: In a condition likely to cause a crash or a breakdown

A defect that makes a crash or a breakdown likely has to be corrected before the vehicle is driven, not reported at the end of the trip.

Source: ecfr.gov
Where is the yellow antilock brake malfunction lamp on a trailer, and what does it mean if it stays lit?
1. On the rear doors beside the lamps, and it means the trailer service brakes have locked on that axle set
2. Inside the cab, and it means the parking brake is set
3. On the right rear corner of the trailer, and it means the load has shifted out of balance
4. On the left side, at the front or rear corner, and it means the antilock function may not be working
Show answer

Answer D: On the left side, at the front or rear corner, and it means the antilock function may not be working

Trailers carry the yellow lamp on the left side, and a lamp that stays on after the bulb check means the antilock function may be lost even though the normal brakes still work.

Source: dds.georgia.gov
You want to check whether a tire on your truck is properly inflated. What is the correct method?
1. Measure the pressure with a tire gauge
2. Strike the tread with a mallet and listen to the sound it makes
3. Press on the sidewall with your boot to feel how much it gives
4. Compare its height with the tire on the opposite side of the axle
Show answer

Answer A: Measure the pressure with a tire gauge

Only a tire gauge tells you the actual pressure; a tire can look and sound normal while being badly underinflated.

Source: oregon.gov
During the walkaround you notice one tire on an axle is a radial and the tire next to it is bias-ply. What should you do?
1. Continue, because mixing tire types on one axle is acceptable as long as both are inflated to the same pressure
2. Treat it as a defect, because radial and bias-ply tires must not be mixed on the same axle
3. Continue, because the rule against mixing tire types applies only to the steering axle of a bus
4. Swap the two tires to the rear axle, where mixed construction is permitted on dual wheels
Show answer

Answer B: Treat it as a defect, because radial and bias-ply tires must not be mixed on the same axle

Radial and bias-ply tires flex and grip differently, so mixing them on one axle makes the vehicle handle unpredictably and is not allowed.

Source: oregon.gov
On a set of dual tires, which condition must be reported as a defect?
1. The two tires have valve stems that point in different directions
2. The inner tire carries a different brand name than the outer tire
3. The two tires show slightly different amounts of road dust and dirt
4. The two tires are touching each other or rubbing on part of the vehicle
Show answer

Answer D: The two tires are touching each other or rubbing on part of the vehicle

Duals that touch each other or the vehicle overheat and wear quickly, so they must be separated by proper spacing and inflation before driving.

Source: oregon.gov
Rust streaks are running outward from the lug nuts on one wheel. What does this most likely indicate?
1. The wheel has been recently balanced by a tire shop
2. The brake drum behind the wheel is overheating badly
3. The lug nuts may be loose
4. The tire was mounted with too much lubricant on the bead
Show answer

Answer C: The lug nuts may be loose

Rust trails spreading from the nuts are a classic sign that the nuts have worked loose and the wheel has been moving on the studs.

Source: oregon.gov
After starting the engine, how quickly should the oil pressure gauge come up to its normal range?
1. Only after the engine has warmed up for ten minutes or more
2. Within a few seconds
3. Only once the vehicle has been driven about a mile at low speed
4. Within one minute at high idle with the parking brake released
Show answer

Answer B: Within a few seconds

Oil pressure should build within seconds of starting; if it stays low, the engine is not being lubricated and should be shut down.

Source: oregon.gov
While checking the in-cab gauges after start-up, what should the coolant temperature gauge do?
1. Jump immediately to the top of the scale and then settle back down
2. Stay at the bottom of the scale for the whole trip unless the engine is under load
3. Rise gradually to the normal operating range
4. Move up and down steadily while the engine idles, showing the thermostat is cycling
Show answer

Answer C: Rise gradually to the normal operating range

A healthy cooling system warms the engine slowly; a gauge that shoots up or stays cold points to a problem with the thermostat, coolant or sensor.

Source: oregon.gov
What should the ammeter or voltmeter show once the engine is running?
1. A steady discharge reading, which shows the alternator is being spared
2. A zero reading, which proves that the electrical system is isolated
3. A reading at the maximum end of the scale until the batteries are full
4. A reading in the normal charging range
Show answer

Answer D: A reading in the normal charging range

With the engine running, the alternator should be charging; a discharge reading or an abnormal charge level means an electrical fault.

Source: oregon.gov
How do you test for leaks in a hydraulic brake system during the pre-trip inspection?
1. Pump the pedal three times, then hold firm pressure for five seconds and make sure the pedal does not move
2. Release the parking brake, roll forward at about 15 mph and stop as hard as you can while watching the gauges
3. Press the pedal once lightly and watch whether the brake warning light on the dashboard comes on
4. Start the engine, let it idle for one minute and listen for any hissing sound under the dashboard
Show answer

Answer A: Pump the pedal three times, then hold firm pressure for five seconds and make sure the pedal does not move

If the pedal sinks while you hold pressure, fluid is escaping or air is in the lines, and the vehicle must not be driven until the problem is repaired.

Source: oregon.gov
What is the correct way to test the parking brake before a trip?
1. Release the parking brake on a slight downgrade and time how long the vehicle takes to roll
2. Set the parking brake, shift to neutral and rev the engine to about 2,000 rpm for a minute
3. With the parking brake set, put the vehicle in a low gear and gently try to move forward
4. Apply the service brake and the parking brake together and check the pressure gauge for a drop
Show answer

Answer C: With the parking brake set, put the vehicle in a low gear and gently try to move forward

A parking brake that holds against a gentle pull in low gear is working; if the vehicle moves, the brake needs adjustment or repair.

Source: oregon.gov
You are inspecting the vehicle alone and need to confirm that the stop lights work. Which method is correct?
1. Have a helper press the brake pedal, or apply the brake in a way that keeps it on while you check from outside
2. Look at the reflection in the mirrors while you tap the brake pedal from the driver seat with the doors closed
3. Skip the check, since stop lights are examined only during the annual inspection by a mechanic
4. Turn on the four-way flashers and assume the stop lights share the same bulbs and wiring
Show answer

Answer A: Have a helper press the brake pedal, or apply the brake in a way that keeps it on while you check from outside

Stop lights are checked from outside the vehicle while the brakes are applied, so a helper or a brake held on is needed.

Source: oregon.gov
While you are driving, what should you do to catch a developing problem with the vehicle?
1. Check the gauges regularly and pay attention to unusual sounds, smells or vibrations
2. Stop every 30 minutes to repeat the whole seven-step inspection from the beginning
3. Rely only on the dashboard warning lights, since they cover every part of the vehicle
4. Watch the mirrors constantly and ignore the gauges until the next fuel stop
Show answer

Answer A: Check the gauges regularly and pay attention to unusual sounds, smells or vibrations

Inspection continues during the trip: gauges, mirrors and your senses can reveal a problem long before a warning light does.

Source: oregon.gov
During a trip you stop for a break. Which items should you check before driving on?
1. Only the fuel level and the engine oil, since everything else was covered before the trip started
2. Tires, wheels and rims, brakes, lights, reflectors, electrical connections and cargo securement
3. The windshield washer fluid, the radio, the seat adjustment and the cleanliness of the cab
4. Only the cargo, because the running gear cannot change its condition during a trip
Show answer

Answer B: Tires, wheels and rims, brakes, lights, reflectors, electrical connections and cargo securement

Critical items can change during a trip, so each stop is used to recheck the tires, wheels, brakes, lights, connections and cargo.

Source: oregon.gov
At a stop on a hot day you find a tire that is too hot to touch. What should you do?
1. Let some air out to lower the pressure and continue driving at once
2. Pour cold water on the tire and drive on as soon as it stops steaming
3. Wait until the tire cools before driving on, and do not let air out of it
4. Drive on slowly, because a hot tire with normal pressure cannot fail
Show answer

Answer C: Wait until the tire cools before driving on, and do not let air out of it

A tire that is too hot to touch may be about to fail or catch fire; releasing air only leaves it underinflated once it cools, which makes things worse.

Source: oregon.gov
Study tip. When two answers both seem legal, pick the one that is safer for everyone on the road. That is how most tests are written.
Which windshield condition should be reported during the inspection?
1. A small inspection sticker placed in the lower corner on the passenger side
2. Cracks or dirt that get in the way of your view of the road
3. A slight tint along the top edge that was installed by the manufacturer
4. Water spots left on the glass after the vehicle was washed
Show answer

Answer B: Cracks or dirt that get in the way of your view of the road

The windshield must give a clear view; damage or grime in the driver line of sight is a safety defect.

Source: oregon.gov
What are you checking when you look at the batteries during the engine compartment inspection?
1. That the fluid is filled to the very top of each cell and the case is warm to the touch after starting
2. That the positive cable has been disconnected to prevent the batteries draining while parked
3. That the battery box has been left open so that any gases can escape freely while driving
4. That they are securely mounted, the connections are tight and free of corrosion, and the caps are in place
Show answer

Answer D: That they are securely mounted, the connections are tight and free of corrosion, and the caps are in place

Loose or corroded batteries can fail or short out, so the mount, cables, terminals and vent caps are all part of the check.

Source: oregon.gov
What frame defects are you looking for during the walkaround?
1. Cracks, bends or broken cross members
2. Fresh paint, which can hide areas where the frame was reinforced
3. Small dents in the mud flaps and scratches on the rear bumper
4. A frame that is longer than the body, which shows it was extended
Show answer

Answer A: Cracks, bends or broken cross members

The frame carries the whole load, so cracked or bent rails and broken cross members are serious structural defects.

Source: oregon.gov
In very hot weather, how often should you check the tires during a trip?
1. Only at the start and end of the day, since heat builds slowly
2. Every 30 minutes or every 25 miles, whichever comes first
3. Every eight hours or every 500 miles, whichever comes first
4. About every two hours or every 100 miles
Show answer

Answer D: About every two hours or every 100 miles

Heat raises tire pressure and can lead to blowouts, so tires are checked about every two hours or 100 miles when it is very hot.

Source: oregon.gov
What should you check about the fuel tank during the walkaround?
1. That it is securely mounted, the cap is on tight and there are no leaks
2. That it is completely full, because a partly empty tank can collapse
3. That the cap has been left loose so that pressure cannot build up inside
4. That the tank has been moved forward to balance the steering axle load
Show answer

Answer A: That it is securely mounted, the cap is on tight and there are no leaks

A loose tank or a missing cap can spill fuel, and any fuel leak is a fire hazard that makes the vehicle unsafe to drive.

Source: oregon.gov
You can see a crack in a brake drum that runs across more than half the width of the friction surface. What does this mean?
1. The drum is acceptable as long as the crack does not reach the outer edge of the drum
2. The drum is acceptable on a rear axle but must be replaced if it is on a steering axle
3. The drum is defective and must be repaired before the vehicle is driven
4. The drum only needs to be watched and rechecked at the next fuel stop of the trip
Show answer

Answer C: The drum is defective and must be repaired before the vehicle is driven

Cracks longer than half the width of the friction area mean the drum can break apart under braking heat and must be replaced.

Source: oregon.gov
When should mirror adjustment be checked, and what should each mirror show?
1. Once a week, with each mirror aimed so that no part of the vehicle appears in it
2. Before every trip, with each mirror adjusted to show some part of the vehicle
3. Only after a mirror is hit, with each one aimed straight down at the road surface
4. Only at night, with each mirror turned to reduce headlight glare from behind
Show answer

Answer B: Before every trip, with each mirror adjusted to show some part of the vehicle

Checking the mirrors before each trip and keeping a small part of the vehicle in view gives a reference point for judging distance behind and beside you.

Source: oregon.gov
Which of these is NOT on the federal list of parts and accessories the driver must be satisfied are in good working order before driving?
1. The windshield wipers
2. The rear-vision mirrors
3. The coupling devices
4. The seat cushion upholstery
Show answer

Answer D: The seat cushion upholstery

The federal pre-trip rule names brakes, steering, lights and reflectors, tires, horn, wipers, mirrors, coupling devices, wheels and rims, and emergency equipment; seat upholstery is not on that list.

Source: ecfr.gov
Apart from the legal duty, what is the main practical reason for a thorough pre-trip inspection?
1. It finds problems that could cause a breakdown or a crash before the vehicle is on the road
2. It allows the driver to extend the daily driving window by the length of time the inspection takes
3. It transfers responsibility for the condition of the vehicle to the shop that serviced it last
4. It replaces the need for the annual periodic inspection of the vehicle
Show answer

Answer A: It finds problems that could cause a breakdown or a crash before the vehicle is on the road

A defect found in the yard is an inconvenience, while the same defect found at highway speed can be a crash, so the inspection is where problems are cheapest to fix.
A company mechanic serviced your truck this morning and signed the work order. Do you still have to inspect the vehicle?
1. No, the mechanic signature on the work order replaces the driver inspection for the rest of that day
2. Yes, the driver is still responsible for being satisfied the vehicle is safe
3. Only the tires and the lights need to be checked after shop work
4. Only if the vehicle will cross a state line during the trip
Show answer

Answer B: Yes, the driver is still responsible for being satisfied the vehicle is safe

Shop work does not transfer the duty; the driver who takes the vehicle out remains responsible for being satisfied it is in safe operating condition.
An enforcement officer inspects your vehicle at the roadside and attaches an out-of-service sticker. What may you do?
1. Drive at a reduced speed to the terminal of your choice, provided the hazard lights are used
2. Continue the trip if the shipper confirms that the load is urgent and time sensitive
3. Nothing until the defect is repaired; the vehicle may not be driven
4. Remove the sticker once the defect has been noted on the daily inspection report
Show answer

Answer C: Nothing until the defect is repaired; the vehicle may not be driven

An out-of-service order means the vehicle is unsafe, and no schedule, load or destination allows it to be driven before the defect is corrected.

Source: ecfr.gov
Who may remove an out-of-service sticker from a commercial vehicle?
1. The driver, once the vehicle has been moved off the highway into a safe parking area to await repair
2. Only an authorized person, and only after the defect that caused it has been repaired
3. Any dispatcher who records the defect in the carrier maintenance file
4. The next driver assigned to the vehicle at the start of the following day
Show answer

Answer B: Only an authorized person, and only after the defect that caused it has been repaired

The sticker stays on the vehicle until the repairs are made and an authorized person removes it, so nobody can simply peel it off and drive away.

Source: ecfr.gov
How often must every commercial motor vehicle receive a periodic inspection?
1. At least once every six months
2. At least once every twenty four months
3. At least once every twelve months
4. Only when the vehicle changes ownership
Show answer

Answer C: At least once every twelve months

Federal rules require each commercial motor vehicle to pass a periodic inspection at least once in every twelve month period.

Source: ecfr.gov
What information does an inspection decal on a commercial vehicle carry?
1. The gross vehicle weight rating and the maximum number of axles the vehicle is certified to operate
2. The date of the inspection, where the inspection report is kept, and information identifying the vehicle
3. The name of the driver who was operating the vehicle on the day it was inspected
4. The date the vehicle was first registered and the expiry date of the registration plate
Show answer

Answer B: The date of the inspection, where the inspection report is kept, and information identifying the vehicle

The decal shows when the inspection was done, the name and address of the entity that holds the inspection report, and which vehicle it belongs to, so an officer can confirm the inspection at a glance.

Source: ecfr.gov
How long must the record of a periodic inspection be kept?
1. Fourteen months
2. Six months
3. Three months
4. Five years
Show answer

Answer A: Fourteen months

The periodic inspection report is retained for fourteen months from the date of the report, which covers the full twelve month cycle plus a margin.

Source: ecfr.gov
How long must a motor carrier keep a driver vehicle inspection report and the certification of repairs?
1. One month
2. Three months
3. One year
4. Three years
Show answer

Answer B: Three months

The original report and the certifications attached to it are kept on file for three months from the date the report was prepared.

Source: ecfr.gov
When must a post-trip inspection be made?
1. Only when the vehicle is returned to its home terminal
2. Only at the end of a trip that crosses a state line
3. Once a week, on the last day the vehicle is used
4. At the end of each day the driver operates the vehicle
Show answer

Answer D: At the end of each day the driver operates the vehicle

The post-trip inspection closes out each driving day so that anything found is recorded before the vehicle is handed to the next driver.

Source: ecfr.gov
You find a defect during the pre-trip inspection. What must happen before the vehicle is driven?
1. It must be noted in the log book and then monitored again at each stop along the route
2. It may be deferred to the next scheduled maintenance interval if it is not a brake defect
3. It must be repaired, or the vehicle must not be driven
4. It must be photographed and reported to the shipper before the load is accepted
Show answer

Answer C: It must be repaired, or the vehicle must not be driven

Writing a defect down does not make the vehicle safe; a defect that affects safe operation has to be corrected before the trip starts.
In the seven-step method, what comes immediately after starting the engine and inspecting inside the cab?
1. Test the service brakes while moving slowly forward
2. Begin the walkaround at the left front wheel
3. Check the signal lights from outside the cab
4. Turn off the engine and check the lights
Show answer

Answer D: Turn off the engine and check the lights

Step four shuts the engine down and switches on the lamps needed for driving so the driver can leave the cab and confirm they actually work.
What is checked in step six of the seven-step method?
1. The engine oil level and the coolant level with the engine warm
2. The steering linkage and the front suspension components on both sides
3. The cargo securement devices holding the load on the trailer deck
4. The turn signals and the stop lights, checked from outside the vehicle
Show answer

Answer D: The turn signals and the stop lights, checked from outside the vehicle

Step six returns to the cab to switch on the signal and stop lamps, then checks each one from outside, because those lamps are not lit during the earlier light check.
During the walkaround inspection, where does the driver normally start and how does the check proceed?
1. At the rear of the trailer, working forward along the right side and then back down the left
2. At whichever wheel looks most worn, then outward to the rest of the vehicle
3. At the left front of the vehicle, working around it in a set order that returns to the cab
4. At the engine compartment, which is inspected a second time during the walkaround
Show answer

Answer C: At the left front of the vehicle, working around it in a set order that returns to the cab

The walkaround follows the same route every time, starting at the left front and circling the vehicle, so that nothing is skipped when the driver is tired or rushed.
What are you checking when you pull the engine oil dipstick during the pre-trip?
1. That the oil level is within the safe operating range marked on the stick
2. That the oil has been changed within the last thousand miles of operation
3. That the oil is the same brand as the oil listed on the last work order
4. That the dipstick tube is free of the rust that forms in cold weather
Show answer

Answer A: That the oil level is within the safe operating range marked on the stick

The dipstick shows whether there is enough oil to lubricate and cool the engine, and a level outside the safe range must be corrected before driving.
What is checked about the engine cooling system during the engine compartment inspection?
1. That the radiator hoses have been replaced within the last twelve months of service
2. That the coolant reservoir cap has been removed so pressure cannot build up
3. That the coolant level is adequate and the radiator and hoses are not leaking
4. That the fan belt has been loosened enough to let the fan turn freely by hand
Show answer

Answer C: That the coolant level is adequate and the radiator and hoses are not leaking

A low coolant level or a leaking hose leads to overheating, which can stop the vehicle in a place where stopping is dangerous.
Why should the radiator cap never be removed while the engine is hot?
1. The cooling system is under pressure and scalding coolant can be sprayed out
2. The engine will stall as soon as the pressure in the system is released
3. Removing it while hot voids the annual inspection certificate for the vehicle
4. The cap can only be reseated correctly once the engine has reached full temperature
Show answer

Answer A: The cooling system is under pressure and scalding coolant can be sprayed out

A hot cooling system holds pressurized coolant above its normal boiling point, so releasing the cap can throw boiling liquid and steam at whoever is holding it.
What should be checked about the power steering system in the engine compartment?
1. That the pump is disconnected from the belt drive while the vehicle is parked
2. That the reservoir is filled to the very top of the filler neck at every inspection
3. That the steering wheel is locked in the straight ahead position before the check
4. That the fluid level is correct and the hoses and pump are not leaking
Show answer

Answer D: That the fluid level is correct and the hoses and pump are not leaking

Losing power steering fluid means losing steering assistance, which can happen suddenly and makes a heavy vehicle very hard to turn.
Which components on a typical engine are driven by belts that must be checked for wear and tension?
1. The windshield wipers, the horn compressor and the headlamp leveling motor
2. The starter motor, the fuel injectors and the exhaust manifold assembly
3. The transmission, the differential and the drive shaft support bearing
4. The alternator, the water pump and, on many vehicles, the air compressor
Show answer

Answer D: The alternator, the water pump and, on many vehicles, the air compressor

Belts drive accessories such as the alternator, the water pump and the air compressor, so one failed belt can take out charging, cooling or air supply.
You press on a drive belt and it deflects far more than the others. What does that suggest?
1. The belt is correctly tensioned for a cold engine and will tighten as it warms
2. The belt has been recently replaced and needs no further attention
3. The belt is too loose and the part it drives may not work properly
4. The belt is over-tightened and is straining the bearings in its pulley
Show answer

Answer C: The belt is too loose and the part it drives may not work properly

A belt with excessive play slips on its pulleys, so the accessory it drives turns too slowly or not at all under load.
During the engine compartment check, which leaks are you looking for?
1. Only engine oil, since the other fluids evaporate before they reach the ground
2. Only fluids that leave a colored stain on the pavement under the vehicle
3. Only leaks that appear while the engine is running at operating temperature
4. Fuel, coolant, engine oil, power steering fluid and battery fluid
Show answer

Answer D: Fuel, coolant, engine oil, power steering fluid and battery fluid

Every fluid in the compartment matters, because a fuel leak is a fire risk and a loss of coolant, oil, steering fluid or electrolyte can disable the vehicle.
What should you look for on the electrical wiring in the engine compartment?
1. Worn, frayed or cracked insulation and loose or corroded connections
2. That the wiring loom has been coated with grease to keep moisture out of it
3. That every wire has been replaced with the same color used by the manufacturer
4. That all wires are bundled tightly against the exhaust manifold to keep them clear
Show answer

Answer A: Worn, frayed or cracked insulation and loose or corroded connections

Damaged insulation can short a circuit against the frame or engine, which can kill a lamp you depend on or start a fire.
How is the fluid level in an automatic transmission usually checked?
1. With the engine running, following the procedure in the operator manual
2. Only after the vehicle has stood overnight and is completely cold throughout
3. By weighing the transmission pan before and after the trip is completed
4. By counting the number of shifts the transmission makes in the first mile
Show answer

Answer A: With the engine running, following the procedure in the operator manual

Most automatic transmissions are designed to be checked with the engine running, and the operator manual gives the exact conditions for that vehicle.
Study tip. One test a day for a week beats seven tests in one evening: spaced practice is what makes rules stick.
Your windshield washer reservoir is empty and rain and road spray are expected. What should you do?
1. Note the empty reservoir on the end of day report and leave the refill to the shop
2. Fill it only if the trip is scheduled to run longer than one hundred miles
3. Drive on, since the wipers on their own will handle road spray in any weather
4. Fill it before the trip, because you need the washers to keep the windshield clear
Show answer

Answer D: Fill it before the trip, because you need the washers to keep the windshield clear

Wipers alone smear the film of oil and grit thrown up by traffic, so the washers are part of keeping a usable view of the road.
How is free play in the steering wheel measured during the inspection?
1. By counting the number of full turns of the wheel between the two steering stops
2. By turning the wheel until the front wheels just start to move and noting the movement
3. By pushing and pulling the wheel forward and back along the axis of the steering column
4. By comparing the wheel position with the front axle while driving at highway speed
Show answer

Answer B: By turning the wheel until the front wheels just start to move and noting the movement

Play is the movement at the rim that produces no movement at the road wheels, so it is measured by turning until the wheels first respond.
What is checked about the clutch and the gearshift during the in-cab inspection?
1. That the clutch disc thickness is measured through the inspection cover
2. That the clutch pedal can be held down for the whole of a long descent
3. That the gearshift moves into reverse only when the engine has been stopped
4. That the clutch free play is within the range the manufacturer specifies
Show answer

Answer D: That the clutch free play is within the range the manufacturer specifies

Too little or too much clutch free play causes slipping or dragging, either of which can leave the driver unable to select the gear a hill demands.
What must the driver check about the seat belt during the inspection?
1. That it is securely mounted, adjusts properly and is not ripped or frayed
2. That it has been replaced within twelve months of the date of manufacture
3. That it can be unbuckled with the vehicle in motion during an emergency stop
4. That the belt webbing has been treated with a waterproofing product
Show answer

Answer A: That it is securely mounted, adjusts properly and is not ripped or frayed

A belt only restrains the driver if its anchorage is sound and the webbing is intact, so mounting and condition are both checked.
What must the driver confirm about the required emergency equipment before a trip?
1. That it is in place, in working order and ready to be used
2. That the fire extinguisher was refilled within the last thirty days of use
3. That the warning devices are stored in the trailer where they will stay dry
4. That the spare fuses match the amperage listed on the vehicle registration
Show answer

Answer A: That it is in place, in working order and ready to be used

Federal rules require the driver to be satisfied that the emergency equipment is present and ready, because it is needed at the worst possible moment.

Source: ecfr.gov
What do you check about the fire extinguisher during the pre-trip?
1. That it is stored loose behind the seat where it can be reached quickly
2. That it has been discharged at least once so the mechanism is known to work
3. That it is securely mounted, charged and that you know how to operate it
4. That its pressure gauge reads zero, which shows the seal has never been broken
Show answer

Answer C: That it is securely mounted, charged and that you know how to operate it

An extinguisher must be held in its bracket, show a charged gauge and be understood by the driver, because a fire leaves no time to learn.
What color must the clearance and side marker lamps and reflectors at the front of a trailer be?
1. Amber
2. Red
3. Blue
4. White
Show answer

Answer A: Amber

Amber marks the front and the forward part of the sides of a vehicle, while red marks the rear, so another driver can tell which way the vehicle is facing.

Source: ecfr.gov
Which lamp must make the rear registration plate legible after dark?
1. A red lamp mounted beside the plate
2. An amber lamp mounted above the plate
3. A white lamp that lights the plate
4. The rear turn signal lamps working together
Show answer

Answer C: A white lamp that lights the plate

A white license plate lamp is required so the plate can be read at night, and a burned out one is a defect like any other lamp.
During the walkaround you find the reflective conspicuity tape along the trailer caked with road grime. What should you do?
1. Ignore it, because reflective tape is decorative and is not part of the required lighting system
2. Clean it, because dirty reflective material cannot make the trailer visible at night
3. Cover it with the mud flap so that it cannot get any dirtier during the trip
4. Replace it at the end of the trip and drive with the marker lamps switched on instead
Show answer

Answer B: Clean it, because dirty reflective material cannot make the trailer visible at night

Reflective sheeting only works if light can reach it and bounce back, so a dirty strip leaves the trailer effectively unmarked to approaching traffic.
A brake light lens is cracked and the lamp still lights. How should that be treated?
1. As acceptable, because the lamp still lights and lighting is judged by output alone
2. As a defect, because water can enter and the lamp can dim or fail
3. As acceptable provided the crack is smaller than the diameter of a coin
4. As a defect only if the vehicle is going to be driven after dark
Show answer

Answer B: As a defect, because water can enter and the lamp can dim or fail

A cracked lens lets in water and dirt, which corrodes the socket and dulls the lamp, so it is reported before it becomes a dead brake light.
How should the headlamps be checked during the pre-trip inspection?
1. By switching on both low beam and high beam and confirming each one works outside
2. Only before a trip that will continue after sunset or begin before sunrise
3. By confirming that the dash indicator for the high beam lights up when high beam is selected
4. By comparing the brightness of the two headlamps against a wall at ten paces
Show answer

Answer A: By switching on both low beam and high beam and confirming each one works outside

Both beams are separate circuits, so each is switched on in turn and confirmed from outside the vehicle where the lamps can actually be seen.
You find one lug nut missing from a wheel that has ten studs. What should you do?
1. Drive carefully to the next terminal and have it replaced when you arrive there
2. Nothing, because one missing nut out of ten is within normal tolerance
3. Treat it as a defect and have it repaired before the vehicle is driven
4. Retorque the remaining nuts and continue, checking them again at the next stop
Show answer

Answer C: Treat it as a defect and have it repaired before the vehicle is driven

Every missing fastener loads the others more heavily, and wheel separations usually begin with one nut that nobody replaced.
Why must a bent, cracked or badly seated lock ring be reported?
1. It prevents the antilock brake system from reading that wheel speed correctly
2. It makes the wheel much harder to balance at highway speed
3. It causes hub oil to leak past the axle seal and into the brake drum
4. It can come off under pressure and let the tire and rim separate violently
Show answer

Answer D: It can come off under pressure and let the tire and rim separate violently

The lock ring holds the assembly together against the full pressure of the tire, so a damaged ring can release with enough force to kill.
When is tire pressure most accurately compared with the recommended figure?
1. After a long descent, when the brakes have warmed the wheels and the tires
2. When the tires are cold, before the vehicle has been driven
3. Immediately after an hour of highway running at the legal speed
4. Only when the vehicle is loaded to its maximum gross weight
Show answer

Answer B: When the tires are cold, before the vehicle has been driven

Recommended pressures are cold pressures, so a reading taken before the tires have heated up is the only one that can be compared directly.
After two hours of driving you measure a tire and the pressure reads higher than the cold figure. What should you do?
1. Bleed air out until it matches the cold pressure written on the vehicle placard
2. Nothing, because pressure rises normally as a tire heats up in use
3. Add air, because a hot tire loses pressure steadily through the valve stem
4. Deflate the tire completely and reinflate it once it has cooled down
Show answer

Answer B: Nothing, because pressure rises normally as a tire heats up in use

Air expands as the tire heats, so a higher hot reading is expected, and letting air out leaves the tire underinflated once it cools.
A tire has a cut deep enough to expose the body ply or the belt material. What does that mean?
1. It matters only on a steering axle and not on a drive or trailer axle
2. The tire may be used until the end of the current trip
3. The cut may be filled with rubber sealant and the tire kept in service
4. The vehicle must not be driven on that tire
Show answer

Answer D: The vehicle must not be driven on that tire

Once the structural plies are exposed the casing has lost its strength, and federal rules treat that tire as unfit for the road.

Source: ecfr.gov
During the walkaround you notice a bulge in the sidewall of a trailer tire. What does it indicate?
1. Normal flexing of the sidewall in a tire that is carrying a heavy load
2. Damage inside the tire, which can lead to a sudden failure
3. The tire has been recently mounted and has not yet settled onto the rim
4. The tire pressure is slightly higher than the recommended cold figure
Show answer

Answer B: Damage inside the tire, which can lead to a sudden failure

A bulge means the internal structure has broken and only the rubber is holding the air, so the tire can burst without warning.
Two tires in a dual set have noticeably different diameters. Why is that a problem?
1. The smaller tire wears more slowly and lasts far longer than the larger one
2. The two tires cannot be inflated from the same air line on the vehicle
3. The larger tire carries more than its share of the load and can be overloaded
4. The difference makes the speedometer read considerably lower than the true road speed
Show answer

Answer C: The larger tire carries more than its share of the load and can be overloaded

The taller tire touches the road first and takes most of the weight, so it runs overloaded and hot while the smaller one does little work.
A tire may be regrooved only when what is true?
1. It has already been retreaded at least once by an approved tire shop
2. It carries a marking from the manufacturer showing that it is regroovable
3. It is fitted to a steering axle, where the extra tread depth is needed
4. It has less than half of its original tread depth remaining on the casing
Show answer

Answer B: It carries a marking from the manufacturer showing that it is regroovable

Only casings built with extra rubber under the tread and marked regroovable by the manufacturer may be cut, because others would be grooved into the belts.

Source: ecfr.gov
Federal rules keep recapped and retreaded tires off the front wheels of which vehicle?
1. Any truck tractor pulling a loaded semi-trailer
2. Any bus carrying passengers
3. Any straight truck over 26,000 pounds
4. Any trailer with more than two axles
Show answer

Answer B: Any bus carrying passengers

The federal rule names buses: a bus may not run with regrooved, recapped or retreaded tires on its front wheels, because a steer tire failure with passengers aboard takes away steering control.
What should you check about the tire valve stems during the walkaround?
1. That the caps have all been removed so pressure can be checked quickly
2. That each stem carries a colored band matching the axle it is fitted to
3. That the stems face outward so they can be photographed for the report
4. That the stems are not cut, cracked or leaking and the caps are in place
Show answer

Answer D: That the stems are not cut, cracked or leaking and the caps are in place

A split stem or a missing cap lets air escape or lets dirt into the valve, and either one can flatten a tire between stops.
You hear air escaping from a trailer tire during the pre-trip. What should you do?
1. Add air and start the trip, then check the tire again at the first stop
2. Move the tire to an inner dual position where it carries less of the load
3. Have it repaired or replaced before the vehicle is driven
4. Drive at a lower speed and watch the tire pressure monitor for any change
Show answer

Answer C: Have it repaired or replaced before the vehicle is driven

An audible leak means the tire is failing now, and federal rules do not allow a vehicle to be operated on a flat or leaking tire.

Source: ecfr.gov
Where on a tire is tread depth measured?
1. Across the top of the tread blocks, using the depth of the fine siping
2. At the outer shoulder of the tread, where wear is always greatest on a steer axle
3. In a major tread groove, away from any tie bar or wear indicator
4. On the sidewall, where the manufacturer moulds the original tread depth
Show answer

Answer C: In a major tread groove, away from any tie bar or wear indicator

Depth is taken in a major groove and away from the raised tie bars and wear indicators, which would give a shallower and misleading reading.

Source: ecfr.gov
Why do cracked spring hangers or badly worn shackles matter?
1. They allow the axle to shift out of its correct position under the vehicle
2. They cause the tires to wear evenly across the whole width of the tread
3. They make the trailer sit higher and change the height of the fifth wheel
4. They increase the load the shock absorbers carry on smooth road surfaces
Show answer

Answer A: They allow the axle to shift out of its correct position under the vehicle

Hangers and shackles hold the spring, and therefore the axle, in place, so when they fail the axle can move and the vehicle may become uncontrollable.
Which shock absorber condition is a defect?
1. A body that is warm to the touch after a long run on a rough road
2. A shock fitted with a dust cover over the upper part of its shaft
3. A shock that is leaking, broken or disconnected at either mounting
4. A shock whose paint has been chipped by stones thrown up by the tires
Show answer

Answer C: A shock that is leaking, broken or disconnected at either mounting

A shock that has lost its fluid or its mounting no longer damps the suspension, so the wheel bounces and loses contact with the road.
What tells you that an air suspension bag has a problem?
1. The bag inflates when the vehicle is loaded and deflates when it is empty
2. The bag is leaking or damaged, or the vehicle sits unevenly on that side
3. The bag is warm after the vehicle has been driven for several hours
4. The bag is made of rubber rather than the steel used in leaf springs
Show answer

Answer B: The bag is leaking or damaged, or the vehicle sits unevenly on that side

An air bag that leaks or is cut lets that corner of the vehicle settle, which throws the load onto the other suspension parts and changes the ride height.
What is the purpose of the torque rods or radius rods you check on the suspension?
1. They hold the axle in alignment with the frame under braking and acceleration
2. They carry the weight of the load directly onto the axle housing
3. They connect the steering linkage to the front axle knuckles on each side
4. They damp out the vertical movement of the leaf springs when the road is rough
Show answer

Answer A: They hold the axle in alignment with the frame under braking and acceleration

Torque rods resist the twisting and fore and aft forces on the axle, so a cracked or missing rod lets the axle move out of alignment.
What do the U-bolts on a leaf spring suspension do?
1. They clamp the spring assembly to the axle so it cannot move
2. They join the two halves of the frame together behind the cab
3. They hold the shock absorber to the lower spring seat only
4. They limit how far the axle can drop when the vehicle is unloaded
Show answer

Answer A: They clamp the spring assembly to the axle so it cannot move

U-bolts hold the spring pack tight against the axle, and a loose or broken U-bolt lets the axle slide out of place under load.
Why does a cracked frame rail or cross member make a vehicle unsafe?
1. It stops the vehicle from passing the annual emissions test at the next inspection
2. The frame carries the whole load, and a crack can spread until the structure fails
3. It makes the cab noisier and lets more vibration reach the driver seat
4. It increases the fuel used per mile because the body flexes more than it should
Show answer

Answer B: The frame carries the whole load, and a crack can spread until the structure fails

The frame is the backbone that supports the body, the load and the running gear, so a crack in it is a structural failure that grows with every mile.
Why is a leaking exhaust system on a commercial vehicle dangerous to the driver?
1. It reduces engine power and increases fuel consumption noticeably on long grades
2. It can let carbon monoxide reach the cab, where it can poison the occupants
3. It makes the exhaust brake work harder than the manufacturer intended it to
4. It causes the engine temperature gauge to read lower than the true value
Show answer

Answer B: It can let carbon monoxide reach the cab, where it can poison the occupants

Exhaust gas contains carbon monoxide, which has no smell and dulls the driver judgment long before it becomes obvious that anything is wrong.
Study tip. Before test day, check on the official agency website which documents and fees you need to bring.
Which exhaust system condition must be reported as a defect?
1. Soot marks on the outside of the stack after several thousand miles of running
2. A section repaired by wrapping tape or patching material around the pipe
3. A stack fitted with a rain cap that closes when the engine is not running
4. A muffler mounted with rubber isolators between it and the frame rail
Show answer

Answer B: A section repaired by wrapping tape or patching material around the pipe

Exhaust parts may not be patched with wrap or tape, because the repair does not contain the gas or the heat and it fails quickly in service.
Why must exhaust components be checked for contact with other parts of the vehicle?
1. Contact makes the exhaust note louder than the legal noise limit allows
2. Hot exhaust parts touching fuel lines, tires or wiring can start a fire
3. Contact reduces the back pressure the engine needs in order to run efficiently
4. Contact prevents the exhaust from being inspected without lifting the vehicle
Show answer

Answer B: Hot exhaust parts touching fuel lines, tires or wiring can start a fire

Exhaust pipes run hot enough to ignite fuel and melt insulation, so they must be kept clear of the fuel system, the tires and the electrical harness.
What are you looking for on the brake drums during the walkaround?
1. That the drums have been painted to protect them against surface corrosion
2. Cracks, dents and any oil or grease that has reached the friction surface
3. That the drum diameter matches the diameter of the wheel rim exactly
4. That the drums are cool to the touch before the vehicle has been driven
Show answer

Answer B: Cracks, dents and any oil or grease that has reached the friction surface

A cracked or badly scored drum can break apart under braking heat, and oil or grease on the friction surface destroys the braking effort at that wheel.
Which brake lining condition must be reported?
1. Linings that are made of a different material from the ones on the trailer
2. Linings that show a light dust on the surface after use on a long grade
3. Linings that are worn thin, loose, cracked or soaked with oil or grease
4. Linings that were replaced during the most recent annual inspection
Show answer

Answer C: Linings that are worn thin, loose, cracked or soaked with oil or grease

Linings must have enough material left and must be securely attached and clean, because a thin, loose or contaminated lining cannot deliver its share of braking.
What happens to braking performance if oil or grease reaches a brake lining?
1. Braking improves, because the lining then slides more smoothly on the drum
2. That brake loses much of its effect and the vehicle can pull to one side
3. The brake locks up permanently and the wheel can no longer turn at all
4. Nothing changes until the lining wears down to its minimum thickness
Show answer

Answer B: That brake loses much of its effect and the vehicle can pull to one side

A contaminated lining cannot grip the drum, so that wheel contributes little braking and the vehicle pulls toward the side that is still working.
What are you checking on the mud flaps during the walkaround?
1. That they are the same color as the trailer and carry the name of the carrier
2. That they can be folded up out of the way whenever the vehicle is loaded
3. That they are securely attached, not torn and not dragging on the ground
4. That they extend far enough forward to cover the front face of the tire
Show answer

Answer C: That they are securely attached, not torn and not dragging on the ground

A flap that is torn or hanging loose stops shielding following traffic from spray and stones, and a dragging flap can catch and tear away on the road.
What must be checked about the cargo doors and any tarpaulin before a trip?
1. That the doors have been sealed by the shipper and the seal number recorded
2. That the doors are closed and latched and that any tarp is tied down securely
3. That the tarp has been folded and stored inside the trailer for the journey
4. That the doors can be opened from the outside without the driver being present
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Answer B: That the doors are closed and latched and that any tarp is tied down securely

An unlatched door or a loose tarp can swing open or tear free at speed, spilling cargo or blocking the view of the traffic behind you.
Cargo carried inside the cab must never do which of these?
1. Be carried in a container that was not supplied by the shipper of the load
2. Weigh more than one quarter of the total weight being carried in the trailer behind it
3. Block the driver view, restrict arm or leg movement, or block an emergency exit
4. Be placed anywhere except directly behind the back of the driver seat
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Answer C: Block the driver view, restrict arm or leg movement, or block an emergency exit

Anything inside the cab must leave the driver a clear view, free movement of the arms and legs, and an unobstructed way out of the vehicle.

Source: ecfr.gov
A load overhangs the rear of the trailer. What must the driver check before leaving?
1. That the overhang has been reported to the shipper and entered on the bill of lading
2. That the overhang is supported by a wheel resting on the road surface
3. That the overhang is no longer than the distance between the trailer axles
4. That the overhang is marked as required, with flags or lamps as conditions demand
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Answer D: That the overhang is marked as required, with flags or lamps as conditions demand

A projecting load has to be made visible to other drivers, with flags in daylight and lamps when lights are required, so nobody runs into what they cannot see.
What is the purpose of the header board, or headache rack, that you inspect behind the cab?
1. It protects the driver from cargo that shifts forward during a hard stop
2. It carries the weight of the front of the load while the vehicle is turning
3. It provides the mounting point for the trailer air and electrical lines
4. It marks the legal front limit of the cargo carrying area of the vehicle
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Answer A: It protects the driver from cargo that shifts forward during a hard stop

In a hard stop the load keeps moving forward, and the header board is the barrier between that load and the back of the cab.
Before starting a trip, what must the driver confirm about the weight of the loaded vehicle?
1. That it is within the legal gross and axle limits for the route being driven
2. That it matches the weight shown on the last annual inspection report
3. That it is at least half of the rated capacity of the trailer being pulled
4. That it has been recorded on the driver daily log for the previous day
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Answer A: That it is within the legal gross and axle limits for the route being driven

Overweight vehicles brake poorly, damage tires and suspension components, and can be put out of service at a scale, so weight is checked before the wheels turn.
With the tractor coupled to the trailer, what should you see between the upper and lower fifth wheel plates?
1. No space at all between the two plates
2. A gap of about one inch, which allows the trailer to pivot during a turn
3. A gap wide enough to see the locking jaws from the driver side of the tractor
4. A gap filled with grease so that the two plates never make direct contact
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Answer A: No space at all between the two plates

Any daylight between the plates means the trailer is not properly seated on the fifth wheel and the coupling can come apart under load.
After coupling, where should the fifth wheel release handle be?
1. In the locked position with the safety latch in place
2. Pulled out, so that the jaws can be inspected from below the trailer
3. Removed and stowed inside the cab until the trailer is dropped again
4. Held out by the landing gear crank handle for the duration of the trip
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Answer A: In the locked position with the safety latch in place

The handle must be pushed in and latched, because a handle left out means the jaws can open and release the trailer while you are driving.
How do you confirm that the coupling is locked before pulling out of the yard?
1. By checking that the air lines to the trailer are pressurized to the correct level
2. By opening the trailer doors and looking down at the kingpin from inside the trailer
3. By raising the landing gear and watching for the trailer to settle onto the plate
4. By locking the trailer brakes and pulling gently forward against them
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Answer D: By locking the trailer brakes and pulling gently forward against them

The tug test loads the coupling in the direction that would pull it apart, so if the jaws are not closed on the kingpin you find out at walking pace.
What must be checked on a sliding fifth wheel during the inspection?
1. That it has been moved fully to the rear for every trip regardless of the load
2. That it is locked in position and not so far forward that the trailer can hit the cab
3. That the slide rails have been greased until the fifth wheel moves freely along them
4. That the locking pins have been removed so that the fifth wheel can adjust during turns
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Answer B: That it is locked in position and not so far forward that the trailer can hit the cab

A slider that is unlocked can move under braking, and one set too far forward lets the trailer strike the cab when the tractor turns sharply.
What should you check about the air hoses and the electrical cord running to the trailer?
1. That they are exactly the same length so that they cannot become tangled in a turn
2. That they are coiled tightly around the catwalk rail to keep them out of the way
3. That they are disconnected whenever the trailer is loaded above half its capacity
4. That they are free of damage, properly connected and not dragging or rubbing
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Answer D: That they are free of damage, properly connected and not dragging or rubbing

Lines that chafe on the frame or drag on the road wear through, and a broken line takes away trailer braking or trailer lighting without warning.
What must be true of the trailer landing gear before you move off?
1. Lowered until the pads are just touching the ground so the trailer stays steady
2. Fully raised, with the crank handle secured and no missing or damaged parts
3. Raised halfway, so that it can be dropped quickly if the coupling should fail
4. Left in whatever position the previous driver used when parking the trailer
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Answer B: Fully raised, with the crank handle secured and no missing or damaged parts

Landing gear left part way down can strike a railway crossing or a ramp, and a loose crank handle can swing out into a passing vehicle.
Which items belong to the trailer part of the walkaround inspection?
1. The clutch travel, the gear shift pattern and the engine idle speed under load
2. The windshield, the wiper blades, the mirrors and the output of the heater and defroster
3. The steering linkage, the power steering pump and the alternator drive belt
4. Landing gear, doors, tires, wheels, lights, reflectors, frame and cargo securement
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Answer D: Landing gear, doors, tires, wheels, lights, reflectors, frame and cargo securement

The trailer has its own running gear, lighting, structure and load, and all of it is the responsibility of the driver pulling it.
The engine oil pressure gauge falls toward zero while you are driving. What should you do?
1. Continue to the next fuel stop and add a quart of oil when you arrive
2. Increase engine speed in order to bring the oil pressure back up
3. Stop as soon as it is safe to do so and shut the engine down
4. Switch off the gauge circuit breaker and note the fault on the daily report
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Answer C: Stop as soon as it is safe to do so and shut the engine down

Loss of oil pressure destroys an engine in a very short time, so the correct response is to stop and shut down rather than to drive on.
The coolant temperature gauge climbs above its normal range on a long grade. What is the correct response?
1. Open the radiator cap at the top of the grade to release the pressure
2. Switch off the engine fan so that the engine warms evenly across the block
3. Stop when it is safe to do so and find the cause before going on
4. Keep going and let the descent on the other side cool the engine down
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Answer C: Stop when it is safe to do so and find the cause before going on

Rising coolant temperature signals a fault such as a lost belt, a leak or a blocked radiator, and continuing can turn a repair into a destroyed engine.
Which document must be available to show that the annual inspection was carried out?
1. The driver medical certificate issued at the most recent physical examination
2. The bill of lading for the load being carried at the time of the inspection
3. The inspection report or a copy of it, or a decal displayed on the vehicle
4. A letter from the shipper confirming the vehicle was fit to carry the load
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Answer C: The inspection report or a copy of it, or a decal displayed on the vehicle

Proof of the periodic inspection travels with the vehicle, either as the report itself or as the decal fixed where an inspector can see it.

Source: ecfr.gov
Who must sign a driver vehicle inspection report?
1. The mechanic who last serviced the vehicle
2. The dispatcher who was on duty at the time
3. The shipper of the load being carried
4. The driver who prepared it
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Answer D: The driver who prepared it

The report is the driver statement about the condition of the vehicle at the end of the day, so the driver signs it.

Source: ecfr.gov
At the end of the day you find no defects on a property carrying vehicle. What does the federal rule require?
1. A written report is still required for every vehicle operated during the day
2. No written report is required, although the carrier may still ask for one
3. A written report must be signed by two drivers in order to confirm the finding
4. A written report must be filed with the state agency within twenty four hours
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Answer B: No written report is required, although the carrier may still ask for one

For property carrying vehicles the report is required only when a defect or deficiency is found or reported, although a carrier may impose a stricter policy.

Source: ecfr.gov
What must the motor carrier do about a defect listed on a driver vehicle inspection report?
1. Keep the report on file until the vehicle reaches its next annual inspection date
2. File a copy of the report with the state agency that issued the vehicle registration plate
3. Deduct the cost of the repair from the pay of the driver who reported the defect
4. Repair it, or certify that repair is not needed, before the vehicle is dispatched again
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Answer D: Repair it, or certify that repair is not needed, before the vehicle is dispatched again

A reported defect must be corrected, or certified as not needing correction, and that certification is what the next driver reads before taking the vehicle.

Source: ecfr.gov
What must be true of the person who performs the annual periodic inspection?
1. They must hold a commercial driver license with an air brake endorsement
2. They must be a state enforcement officer working at a fixed weigh station
3. They must be employed directly by the motor carrier that owns the vehicle
4. They must meet the federal qualification requirements for an inspector
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Answer D: They must meet the federal qualification requirements for an inspector

The inspection has to be done by someone who meets the federal training and experience requirements for inspectors, whoever employs them.

Source: ecfr.gov
A vehicle becomes unsafe while you are already on the road. What does the federal rule allow?
1. Continuing only to the nearest place where repairs can safely be made
2. Continuing to the delivery point, provided that the hazard warning lights are used
3. Continuing at a reduced speed until the end of the driver duty period
4. Continuing as far as the home terminal of the carrier in every case
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Answer A: Continuing only to the nearest place where repairs can safely be made

If stopping where you are would be more dangerous than moving, the rule allows you to reach the nearest place where the vehicle can safely be repaired, and no further.

Source: ecfr.gov
Why are the windshield wipers on the pre-trip list even before a trip in fine weather?
1. Because the annual inspection decal is not valid unless the wiper blades are new
2. Because the wiper motor is used to drive the washer pump on most heavy vehicles
3. Because weather can change and a wiper failure leaves the driver without a clear view
4. Because the wipers have to be tested to keep the manufacturer warranty on the glass
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Answer C: Because weather can change and a wiper failure leaves the driver without a clear view

Rain, spray or mud can arrive at any point in a long trip, and a wiper that fails then leaves the driver with no way to clear the windshield.
Your speedometer stops working during the pre-trip check. How should it be treated?
1. As a defect only if the vehicle is fitted with an electronic logging device
2. As acceptable, because engine speed can be used to estimate the road speed
3. As acceptable on a route where the speed limit does not change at any point
4. As a defect, because the driver cannot judge and control speed without it
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Answer D: As a defect, because the driver cannot judge and control speed without it

A working speedometer is required equipment, because judging speed by feel in a heavy vehicle is unreliable and speed governs stopping distance.

Source: ecfr.gov
You pick up a trailer that another driver dropped in the yard. What must you do before pulling it?
1. Pull it to the nearest scale and have the axle weights recorded there first
2. Inspect it yourself, because you are responsible for the whole vehicle you drive
3. Assume the previous driver inspected it and rely on that earlier inspection
4. Ask the yard staff to confirm in writing that the trailer has already been checked over
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Answer B: Inspect it yourself, because you are responsible for the whole vehicle you drive

Responsibility follows the driver who moves the vehicle, and a trailer that has stood in a yard may have lost air, developed a flat tire or been damaged.