Arizona Combination Vehicles CDL Practice Test

This is a free 20-question practice test for the Combination Vehicles portion of the Arizona Commercial Driver's License knowledge exam. Questions are pulled from a pool of 55 drawn from the AAMVA CDL Manual, which is the source document the Arizona Motor Vehicle Division uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in Arizona.

Question 1 of 20

A combination vehicle on slippery roads should be driven:

Faster to maintain control
Slower with greater following distance
At normal speed
In a higher gear

Correct. Reduce speed by at least one third on wet roads and one half on snow; double following distance on slick surfaces.

Question 2 of 20

On a slippery surface, drive in:

Higher gears at higher RPM
A gear that minimizes torque to the drive wheels and brake earlier and gentler
The lowest gear
Whatever is fastest

Correct. Reduce engine power to drive wheels (higher gear, gentler accelerator) and brake earlier and gentler to avoid wheel spin or skid.

Question 3 of 20

When you cross railroad tracks in a tractor-trailer, you should:

Shift gears to maintain speed
Cross in a single gear without shifting, and never start across without room to clear the rails
Stop on the tracks if the light turns red
Honk repeatedly

Correct. Crossing in one gear (without shifting) prevents stalling on the tracks. Never enter a crossing unless you can clear it without stopping.

Question 4 of 20

After connecting the trailer, before pulling away, you should always:

Visually inspect the fifth-wheel/kingpin connection from outside the cab
Just trust the gauge
Honk the horn
Set the trailer brake

Correct. Always visually confirm: no gap between fifth wheel and trailer plate, jaws closed around the kingpin shank, locking lever fully in place.

Question 5 of 20

When inspecting the kingpin during pre-trip, look for:

Excessive wear, bending, cracks, or improper lock-jaw engagement
Only the color
Only the size
Only the grease

Correct. A worn, cracked, or bent kingpin can fail under load. The locking jaws must close completely around the shank, not just the head.

Question 6 of 20

The "rearward amplification" effect:

Is greatest in the lead trailer
Is greatest in the rear-most trailer of doubles or triples
Does not exist
Is the same in every trailer

Correct. Rearward amplification — the crack-the-whip effect — is most severe in the rear trailer of a multi-trailer combination.

Question 7 of 20

Trailer rollover is more likely when:

Cargo is loaded low and centered
Cargo is loaded high or to one side, raising the center of gravity
Cargo is light
Trailer is empty

Correct. High cargo and uneven side-loading raise the center of gravity, increasing rollover risk on curves and ramps.

Question 8 of 20

When you are backing a trailer to the right, you should turn the steering wheel:

Left to start the trailer right
Right to start the trailer right
In the same direction every time
Never use the steering wheel; just push

Correct. When backing, the trailer goes opposite to the way you initially turn the steering wheel. To make the trailer go right (passenger side), start by turning the wheel left.

Question 9 of 20

Length and weight increase what about a combination vehicle?

Stopping distance, off-tracking, blind spots, and time required for lane changes
Visibility
Speed
Acceleration

Correct. Longer, heavier rigs need more stopping distance, swing wider in turns, have larger blind spots, and require more time and space to change lanes.

Question 10 of 20

When you couple, the locking jaws of the fifth wheel must close around:

The kingpin shank, not just the head
Just the head
The trailer skirt
The wheel

Correct. The locking jaws must engage the kingpin shank below the head. If the jaws close above the head, the connection is unsafe.

Question 11 of 20

The air lines connecting the tractor and trailer are:

Red (emergency) and blue (service)
Red and yellow
Blue and yellow
Black and red

Correct. The red glad-hand carries emergency/supply air; the blue glad-hand carries service air. They cross to keep matched colors when coupling.

Question 12 of 20

A sliding fifth wheel allows you to:

Adjust the weight distribution between drive axles and trailer axles
Speed up
Slow down
Disable the trailer brakes

Correct. Sliding fifth wheels move forward to put more weight on drive axles or aft to reduce drive-axle weight, helping comply with axle-weight limits.

Question 13 of 20

A combination vehicle requires more time to stop than a single vehicle because:

It is much heavier and air must travel further to reach the trailer brakes
It accelerates faster
It is shorter
Drivers wait longer

Correct. Greater weight + brake-lag in long air lines = longer stopping distance. Plan ahead.

Question 14 of 20

Which is the proper following distance for a 60-foot rig at 50 mph?

3 seconds
6 seconds
7 seconds
12 seconds

Correct. 1 second per 10 feet at speeds below 40 mph, plus 1 extra second above 40. 60 feet = 6 seconds + 1 = 7 seconds at highway speed.

Question 15 of 20

When backing a tractor-trailer in a straight line, you should:

Let the trailer drift wherever it goes
Make small steering corrections to keep the trailer in line
Apply heavy brake pressure
Use the trailer hand valve

Correct. When backing straight, watch the trailer in your mirrors and make small steering corrections to keep it tracking straight. Big corrections lead to jackknifing.

Question 16 of 20

A sliding-tandem trailer allows you to:

Adjust the trailer-axle position to redistribute weight between trailer axles and tractor drive axles
Speed up
Cool the load
Steer the trailer

Correct. Sliding tandems shift trailer axles forward (more weight on tractor) or aft (more weight on trailer axles), helping meet axle-weight limits.

Question 17 of 20

When uncoupling, you should lower the landing gear:

After releasing the jaws
Before releasing the jaws so the trailer is supported when you pull away
Halfway
Not at all

Correct. Lower the landing gear and snug it against the ground before releasing the fifth-wheel jaws so the trailer doesn't drop when you pull away.

Question 18 of 20

When making a U-turn, a tractor-trailer needs:

Less space than a car
Substantially more space than a car — often more than a single intersection allows
The same space as a car
No turning space

Correct. Tractor-trailer turning radius is much larger than a car. A standard intersection rarely allows a U-turn — find a wider turning area.

Question 19 of 20

Your trailer ABS warning lamp is on. The trailer service brakes:

Will not work at all
Still work normally — only ABS function is unavailable
Lock up
Apply automatically

Correct. Trailer service brakes still work normally without ABS. Have the system repaired; ABS gives extra control during emergency braking.

Question 20 of 20

Combination vehicles are usually:

Easier to drive than single trucks
Harder to drive than single trucks because of length, weight, and the unique handling of articulated vehicles
The same as single trucks
Faster than single trucks

Correct. Combination vehicles (tractor-trailer rigs) are heavier, longer, and articulate at the fifth wheel — all making them more demanding than single-unit trucks.

About the Arizona Combination Vehicles exam

Most states administer 20 Combination Vehicles questions and require 80% to pass. The exam emphasizes the unique handling of articulated vehicles: how trailers track behind the tractor, how to prevent rollover, how to manage rearward amplification with multi-trailer combinations, and the correct sequence to couple and uncouple.

The Arizona Motor Vehicle Division follows the federal CDL standards established by FMCSA. To earn the Combination Vehicles credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full Combination Vehicles question bank or browse all Arizona CDL practice tests.