Vermont · Combination Vehicles CDL Practice Test

The same federal Combination Vehicles question pool used by the Vermont Department of Motor Vehicles, with 50 practice questions and detailed explanations.

About the Combination Vehicles exam in Vermont

To add the Combination Vehicles endorsement to a CDL issued by Vermont, drivers complete the same federal knowledge exam covered on this site, then pay Vermont's endorsement add-on fee of approximately $13 per endorsement. The state schedules the written test at most full-service driver license offices and accepts walk-ins at many locations, though appointments are encouraged in metropolitan areas.

The Combination Vehicles (CV) test in Vermont draws from the same federal question pool used nationwide. Practice with the questions on this page reflects the topics, format, and difficulty you will encounter at the counter. Some states also require an additional state-specific supplement for certain endorsements; check Vermont's CDL manual cover page for any state-specific addenda before your test date.

Once the Combination Vehicles endorsement is added, it appears as the letter CV on the back of your physical license and in the state CDLIS record visible to employers and motor carrier safety auditors. The endorsement remains valid as long as the underlying CDL stays current and any federal prerequisites — such as the TSA security threat assessment for Hazmat — remain in good standing.

For drivers preparing for the Combination Vehicles endorsement test in Vermont, additional context — including federal manual excerpts, employer hiring practices, and DOT medical guidance — is widely available from industry resources. Continue reading on a recommended industry resource for further detail. Always cross-check anything you read with the current edition of your state CDL manual, since enforcement guidance is updated periodically.

How to schedule the written test in Vermont

Most the Vermont Department of Motor Vehicles offices accept walk-in CDL written-test applicants during posted hours, though appointments are strongly recommended in larger metro areas to avoid long waits. Bring your current driver's license, a current DOT medical examiner's certificate, and any documents required to satisfy the federal REAL ID identity-and-residency check if you have not already done so.

If you fail the Combination Vehicles exam in Vermont, you can retake it after a state-determined waiting period (commonly one business day, but in some counties, longer). Most jurisdictions cap the number of retakes within a single application cycle; check with your local the Vermont Department of Motor Vehicles office to confirm.

Combination Vehicles · Practice Quiz

Same federal question pool. Read the question, choose the best answer, then expand the explanation.

Question 1

Before backing under a trailer, the trailer brakes should be:
- A Released
- B Disconnected
- C Set (locked) Correct answer
- D Bled down
Show explanation

Trailer brakes must be set so the trailer does not roll backward as the tractor backs under it.
Question 2

After backing under the trailer, you should test the connection by:
- A Driving forward at speed
- B Releasing the trailer brakes
- C Pulling forward gently against the locked trailer brakes (tug test) Correct answer
- D Disconnecting all lines
Show explanation

The tug test confirms the fifth-wheel jaws are locked around the kingpin. If the trailer moves with the tractor, the lock is good.
Question 3

After the tug test, you should visually inspect the fifth-wheel connection by:
- A Using the dashboard cam only
- B Just walking past
- C Looking for any gap between the trailer apron and the fifth-wheel surface, and checking that the locking jaws are closed around the kingpin Correct answer
- D Honking the horn
Show explanation

A gap between the trailer apron and fifth-wheel indicates the kingpin is not seated. Visually verify and feel the locking lever is fully engaged.
Question 4

The trailer landing gear should be:
- A Removed
- B Halfway down
- C Lowered
- D Fully raised before pulling away Correct answer
Show explanation

Driving with landing gear partially extended risks catching it on bumps, dock plates, or railroad crossings. Fully raise and stow the crank handle.
Question 5

Off-tracking is when:
- A The tractor lifts off the road
- B The trailer slides sideways
- C The rear wheels of a turning trailer follow a tighter path than the front wheels of the tractor Correct answer
- D The wheels lose air
Show explanation

Off-tracking causes the trailer to "cut in" on turns. Compensate by swinging wider, especially on tight right turns where curbs and pedestrians are at risk.
Question 6

On a right turn at an intersection, you should:
- A Use the left turn lane
- B Swing wide enough that the trailer wheels clear the curb on the inside Correct answer
- C Stay tight to the curb
- D Cut across the corner
Show explanation

Tight right turns risk the trailer riding the curb and possibly hitting pedestrians. Swing the tractor wide enough that the trailer's inside wheels clear the corner.
Question 7

A trailer skid can be caused by:
- A Underinflated steer tires
- B Trailer brakes locking up while the tractor is still rolling Correct answer
- C Excessive engine power
- D Tractor wheels spinning
Show explanation

Locked trailer brakes lose lateral grip; the trailer pivots around the fifth wheel, producing a jackknife. Release brakes to recover.
Question 8

If the trailer begins to skid, you should:
- A Push the throttle
- B Brake harder
- C Release the brakes to allow the trailer wheels to roll again Correct answer
- D Steer hard left
Show explanation

Releasing brakes restores rolling friction and steering. Once straight, reapply brakes more gently.
Question 9

A "jackknife" is when:
- A The truck rolls over
- B The fifth wheel breaks
- C The trailer disconnects
- D The tractor and trailer fold toward each other forming a sharp angle Correct answer
Show explanation

A jackknife is the sharp folded position between tractor and trailer caused by trailer skid. Recovery requires releasing the brakes immediately.
Question 10

A tractor jackknife is recovered by:
- A Releasing the brakes and steering in the direction the rear of the tractor needs to go Correct answer
- B Locking the brakes harder
- C Using the parking brake
- D Pulling the trailer hand valve
Show explanation

Tractor jackknife (drive-wheel skid) is recovered by releasing brakes/throttle and counter-steering. Lock-on braking makes it worse.
Question 11

In addition to a regular pre-trip, combination vehicles require:
- A Only fuel level checks
- B Only tire pressure
- C Inspection of the coupling system, fifth wheel, kingpin, air lines, and electrical lines Correct answer
- D No additional inspection
Show explanation

The coupling system is the highest-stakes failure point on a combination vehicle and must be inspected every trip.
Question 12

A "skid plate" on the trailer:
- A Holds the cargo
- B Houses the brakes
- C Is the surface that contacts the fifth wheel — must be flat and lubricated Correct answer
- D Is mounted on the tires
Show explanation

The trailer's upper coupler (skid plate) rides on the fifth wheel. It must be smooth, lubricated with fifth-wheel grease, and free of cracks.
Question 13

A pintle hook is used:
- A To inflate tires
- B To set the parking brake
- C To check fluid levels
- D To couple a converter dolly to a trailer Correct answer
Show explanation

Pintle hooks are eye-and-hook couplers used to attach converter dollies in double/triple combinations.
Question 14

If the trailer is skidding to the right, you should:
- A Use the trailer hand valve
- B Steer hard left
- C Brake harder
- D Release the brakes and let it straighten before reapplying gently Correct answer
Show explanation

Release brakes first. Steering input cannot fix a brake-induced skid until the wheels are rolling again.
Question 15

When parking a combination vehicle, you should:
- A Use only the trailer parking brake
- B Use only the trailer hand valve
- C Apply the tractor parking brake — and chock the wheels if grade conditions warrant Correct answer
- D Leave both released
Show explanation

Tractor parking brake (with both tractor and trailer brakes set, on most equipment) provides the most reliable parking lock.
Question 16

Combination vehicles need more space to:
- A Refuel
- B Park overnight
- C Stop, turn, and complete lane changes Correct answer
- D Pass at low speed
Show explanation

Length and weight increase stopping distance, off-tracking on turns, and gap-clearance requirements for lane changes.
Question 17

When meeting an oncoming vehicle on a narrow road:
- A Slow down to give the other vehicle more room Correct answer
- B Honk and accelerate
- C Move into the oncoming lane
- D Maintain speed
Show explanation

Slowing reduces closing speed and leaves more reaction time for both drivers in tight situations.
Question 18

When you are passing a slower vehicle on a highway, you should:
- A Honk continuously
- B Drive in the slower vehicle's blind spot
- C Complete the pass quickly and avoid prolonged side-by-side driving Correct answer
- D Stay alongside for visibility
Show explanation

Prolonged side-by-side driving creates blind-spot risk. Pass with deliberate speed and return to the right lane when safe.
Question 19

When approaching a long downgrade, the proper technique is to:
- A Slow before the descent and shift to a lower gear Correct answer
- B Keep the highest gear
- C Coast in neutral
- D Accelerate down the grade
Show explanation

Slowing and downshifting before the descent allows engine braking to do the work, sparing the service brakes.
Question 20

Engine brakes work best:
- A Only at idle
- B On dry, level roads
- C On long downhills, in conjunction with appropriate gear selection Correct answer
- D On packed snow
Show explanation

Engine brakes absorb downhill kinetic energy. Disengage on slick roads where they could cause drive-wheel skid.
Question 21

When connecting the air lines, the line with the red glad hand goes to:
- A The fuel line
- B The electrical pigtail
- C The trailer's service line
- D The trailer's emergency (supply) line Correct answer
Show explanation

Red supply (emergency) connects to red supply on the trailer. Yellow service connects to yellow service.
Question 22

After connecting the air lines, you should:
- A Connect the electrical line first
- B Drive away immediately
- C Charge the trailer brakes by pushing in the trailer air supply knob Correct answer
- D Disconnect them again
Show explanation

Push the trailer air supply (red eight-sided knob) in to send air to the trailer and release its spring brakes — but only after a successful coupling.
Question 23

The fifth wheel jaws should:
- A Close around the kingpin head only
- B Be removed
- C Stay open
- D Close completely around the kingpin shank Correct answer
Show explanation

The jaws close around the cylindrical shank of the kingpin, not the head. A high hitch (jaws closed around the head) can release in transit.
Question 24

Before driving, the locking lever on the fifth wheel should be:
- A Removed
- B Tied with rope
- C Disengaged
- D Engaged and the safety latch in place Correct answer
Show explanation

Visually verify lever engagement and safety latch. A disengaged lever means the kingpin is not actually locked.
Question 25

When uncoupling, you should lower the landing gear:
- A Halfway only
- B Until it is bearing all the trailer weight
- C Until it firmly contacts the ground but with weight still mostly on the fifth wheel Correct answer
- D After releasing the fifth wheel
Show explanation

Lower until firm contact, then continue cranking only after the fifth wheel is released so the gear takes the load gradually.
Question 26

The order of operations for uncoupling is:
- A Disconnect lines first, then drive away
- B Pull tractor first
- C Lower landing gear, disconnect lines, release fifth-wheel lock, slowly pull tractor out Correct answer
- D Release lock, drive away, then lower gear
Show explanation

Always: secure trailer (chock if needed), lower landing gear to support weight, disconnect lines, release fifth wheel, then ease the tractor out.
Question 27

Trailers built after March 1, 1998 have:
- A Antilock braking systems Correct answer
- B Mechanical braking only
- C Hydraulic brakes
- D No braking systems
Show explanation

Federal regulations required ABS on all new air-braked trailers built on or after March 1, 1998.
Question 28

A yellow ABS warning lamp on the trailer or dolly indicates:
- A Tire failure
- B Engine failure
- C Total brake failure
- D ABS malfunction — the brakes still work, but the system needs service Correct answer
Show explanation

Yellow lamp signals ABS fault. Standard service brakes still function; have the system serviced.
Question 29

When checking the rear of the trailer, you should verify:
- A The fuel cap
- B Only the lights
- C Only the load
- D Lights, reflectors, license plate, mud flaps, and load securement at the rear doors Correct answer
Show explanation

Rear inspection includes lights, reflectors, plate, mud flaps, and visible load securement at the doors.
Question 30

A "high hitch" is dangerous because:
- A The fifth wheel jaws have closed around the head of the kingpin instead of the shank, allowing the trailer to release in transit Correct answer
- B It blocks the mirrors
- C It disables the lights
- D It causes engine overheating
Show explanation

A high hitch occurs when the trailer apron is too high during coupling. The jaws "close" but only on the kingpin head, which can release. Always recheck after coupling.
Question 31

When coupling, you should approach the trailer:
- A In reverse only at idle
- B Slowly and in a straight line, lining up the kingpin with the fifth wheel Correct answer
- C At an angle for visibility
- D At full speed
Show explanation

Approach in a straight line, slowly. Misalignment scrubs tires and can damage the fifth-wheel ramp.
Question 32

A loaded combination vehicle takes longer to stop than a comparable straight truck because:
- A Greater mass and additional braking lag in the trailer brakes Correct answer
- B Better traction
- C Smaller tires
- D Less wind resistance
Show explanation

More weight requires more energy dissipation; trailer brake lag adds to total stopping distance.
Question 33

On a long downgrade, you should brake to a speed:
- A Use brakes lightly continuously
- B About 5 mph below your "safe speed," then release and let engine braking hold the speed Correct answer
- C Just above your safe speed
- D Brake only at the bottom
Show explanation

Apply briefly and firmly to drop 5 mph, then release. This snub-and-release method prevents brake fade.
Question 34

If your brakes fail on a downgrade and a runaway ramp is available:
- A Use it without hesitation Correct answer
- B Coast in neutral
- C Try to make it to the bottom first
- D Use the parking brake only
Show explanation

Runaway ramps stop you safely. Vehicle damage from the ramp is trivial compared to a runaway crash.
Question 35

When loading a combination vehicle, weight should be:
- A Loaded only at the front
- B Stacked as high as possible
- C Distributed to keep the center of gravity low and balanced Correct answer
- D Loaded only at the rear
Show explanation

Low, balanced loading keeps the center of gravity low and reduces rollover risk and tire wear.
Question 36

A high center of gravity:
- A Improves turning
- B Increases the risk of rollover, especially in turns Correct answer
- C Reduces tire wear
- D Has no effect on handling
Show explanation

High center of gravity makes the vehicle prone to rolling over in fast turns or off-ramp curves.
Question 37

The trailer hand valve (or trolley valve), if used to stop the truck, can cause:
- A Tire blowout
- B Engine failure
- C Mirror damage
- D Trailer skid (jackknife) Correct answer
Show explanation

Hand-valve-only stops apply only the trailer brakes, which can lock and skid. Use foot valve for primary braking.
Question 38

When pulling an empty trailer, stopping distance:
- A Is always shorter
- B Is unaffected
- C Can be longer than when loaded because empty trailers may bounce and lock up Correct answer
- D Is the same as loaded
Show explanation

Empty trailers have less weight on the brakes, less tire-to-road force, and may bounce — leading to wheel lockup and longer stops.
Question 39

A drive-wheel skid is caused by:
- A Cargo shifting
- B Bald steer tires only
- C Too much power, too much braking, or oversteering Correct answer
- D High beam use
Show explanation

Drive-wheel skids result from inputs that exceed available traction. Reduce input — release brake/throttle — and counter-steer.
Question 40

A front-wheel skid means:
- A The vehicle continues straight despite steering input — usually from too much braking or oversteering Correct answer
- B The trailer is jackknifing
- C The brakes have failed
- D The drive wheels are spinning
Show explanation

Front-wheel skids occur when steer-tire grip is exceeded. Release brake or throttle and let the front tires regain grip before steering.
Question 41

Before backing under the trailer, you should:
- A Make sure the trailer kingpin and apron are at the correct height — apron slightly above the fifth wheel Correct answer
- B Raise the apron high above
- C Remove the apron
- D Lower the apron well below
Show explanation

The apron should be slightly above the fifth wheel so the trailer rises up onto it as you back under. Too low and the kingpin slides over the fifth wheel; too high and you risk a high hitch.
Question 42

Wheel chocks should be used:
- A Only at fueling stations
- B Only when an inspector is present
- C Only on dirt roads
- D When parking on grades or dropping a trailer Correct answer
Show explanation

Chocks prevent rolling during uncoupling and on grades. They are inexpensive insurance against runaway trailers.
Question 43

During the in-route inspection, you should check the trailer for:
- A Only the load weight
- B Only fuel level
- C Only mirror cleanliness
- D Cargo shift, securement integrity, and obvious mechanical issues Correct answer
Show explanation

In-route checks focus on cargo shift, securement device tension, and any obvious mechanical issue (smoke, smells, sounds).
Question 44

A shifted cargo can:
- A Improve fuel economy
- B Reduce stopping distance
- C Have no effect
- D Make the vehicle hard to handle and increase rollover risk Correct answer
Show explanation

Cargo shift can move the center of gravity dangerously, change weight distribution across axles, and overload tires or brakes.
Question 45

A 53-foot trailer requires roughly how many seconds of following distance at 55 mph?
- A 4 seconds
- B 2 seconds
- C About 7 seconds Correct answer
- D 12 seconds
Show explanation

Tractor 15ft + trailer 53ft = ~68ft total = ~7 seconds at the 1-second-per-10-feet rule plus the over-40 mph addition.
Question 46

When driving on a highway and traffic ahead slows, you should:
- A Honk continuously
- B Activate emergency flashers if you are forced well below traffic speed Correct answer
- C Stop on the road
- D Brake hard suddenly
Show explanation

Four-way flashers warn following traffic of unusual speeds. Use them when you are forced significantly below the flow.
Question 47

A sleeper berth in a CMV:
- A Can be any size
- B Must meet federal minimum size, ventilation, and exit standards Correct answer
- C Does not need an exit
- D Is for personal use only
Show explanation

49 CFR §393.76 specifies minimum sleeper berth dimensions, ventilation, exit, and integration with the cab.
Question 48

Reflective tape on the rear and sides of trailers built after 1993:
- A Is required by federal regulation for visibility at night Correct answer
- B Is decorative
- C Is forbidden
- D Is optional
Show explanation

Federal conspicuity rules require red-and-white reflective tape on most trailers to make the vehicle visible at night and in low light.
Question 49

Inspect the air lines for:
- A Length only
- B Brand
- C Color matching only
- D Damaged lines, leaks, and proper routing without crimping or rubbing Correct answer
Show explanation

Damaged lines fail under pressure. Lines should be properly routed without rubbing on the frame or being crimped at the catwalk.
Question 50

When following another vehicle, you should:
- A Pass on the right
- B Stay just behind it
- C Match its braking exactly
- D Maintain enough space to stop without hitting it if it brakes suddenly Correct answer
Show explanation

Adequate following distance is the single most effective rear-end-collision prevention measure.

Vermont · Combination Vehicles CDL Practice Test

About the Combination Vehicles exam in Vermont

How to schedule the written test in Vermont

Before backing under a trailer, the trailer brakes should be:

After backing under the trailer, you should test the connection by:

After the tug test, you should visually inspect the fifth-wheel connection by:

The trailer landing gear should be:

Off-tracking is when:

On a right turn at an intersection, you should:

A trailer skid can be caused by:

If the trailer begins to skid, you should:

A "jackknife" is when:

A tractor jackknife is recovered by:

In addition to a regular pre-trip, combination vehicles require:

A "skid plate" on the trailer:

A pintle hook is used:

If the trailer is skidding to the right, you should:

When parking a combination vehicle, you should:

Combination vehicles need more space to:

When meeting an oncoming vehicle on a narrow road:

When you are passing a slower vehicle on a highway, you should:

When approaching a long downgrade, the proper technique is to:

Engine brakes work best:

When connecting the air lines, the line with the red glad hand goes to:

After connecting the air lines, you should:

The fifth wheel jaws should:

Before driving, the locking lever on the fifth wheel should be:

When uncoupling, you should lower the landing gear:

The order of operations for uncoupling is:

Trailers built after March 1, 1998 have:

A yellow ABS warning lamp on the trailer or dolly indicates:

When checking the rear of the trailer, you should verify:

A "high hitch" is dangerous because:

When coupling, you should approach the trailer:

A loaded combination vehicle takes longer to stop than a comparable straight truck because:

On a long downgrade, you should brake to a speed:

If your brakes fail on a downgrade and a runaway ramp is available:

When loading a combination vehicle, weight should be:

A high center of gravity:

The trailer hand valve (or trolley valve), if used to stop the truck, can cause:

When pulling an empty trailer, stopping distance:

A drive-wheel skid is caused by:

A front-wheel skid means:

Before backing under the trailer, you should:

Wheel chocks should be used:

During the in-route inspection, you should check the trailer for:

A shifted cargo can:

A 53-foot trailer requires roughly how many seconds of following distance at 55 mph?

When driving on a highway and traffic ahead slows, you should:

A sleeper berth in a CMV:

Reflective tape on the rear and sides of trailers built after 1993:

Inspect the air lines for:

When following another vehicle, you should: