The tractor's rear wheels start to slide sideways (tractor jackknife). What should you do?

Release brakes and accelerate hard

Why should you not fan the brakes on dry pavement?

It wastes air and helps nothing

It is the best way to stop fast

Before operating the starter on a manual tractor, what should you do?

Set the parking brake, clutch in, neutral

Pump the brake pedal several times

Open the trailer supply valve fully

Release the parking brake, select first

Ontario Class A (AZ) overview

Ontario Class A (AZ): Controls, braking and jackknife control

Starting and moving off, transmissions and clutch brakes, the inter-axle differential lock, balanced braking with a trailer, the trailer hand valve, jackknife responses, downgrades and parking a combination.

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Controls, braking and jackknife control · Question 1Score 0/0

The low air-pressure warning comes on while driving. What should you do?

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Study reference: MTO Truck Handbook (online edition, 2026), Ch. 2 Driving — classes A and D — Use of brakes, transmissions, parking

All 22 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

The low air-pressure warning comes on while driving. What should you do?
1. Drive to the next truck stop
2. Pump the brakes to raise pressure
3. Stop at once in the safest place
4. Pull the trailer hand valve
What happens if you let the clutch slip too much?
1. It cools the transmission
2. It overheats and gets damaged
3. It saves fuel on hills
4. It charges the air tanks
The tractor's rear wheels start to slide sideways (tractor jackknife). What should you do?
1. Steer sharply to the right
2. Apply all brakes hard
3. Release brakes and accelerate hard
4. Apply the trailer brakes only
Why should you not fan the brakes on dry pavement?
1. It is the best way to stop fast
2. It locks the trailer wheels
3. It overheats the engine
4. It wastes air and helps nothing
Before operating the starter on a manual tractor, what should you do?
1. Pump the brake pedal several times
2. Set the parking brake, clutch in, neutral
3. Open the trailer supply valve fully
4. Release the parking brake, select first
In which position should the inter-axle differential lock normally be kept?
1. Unlocked
2. Half locked
3. Locked
4. Locked above 50 km/h
Which gear should you generally use to go down a long grade?
1. One gear higher than usual
2. The highest gear available
3. Neutral to save fuel
4. The gear you would climb it in
Your tractor has a clutch brake. When should you push the clutch pedal to the floor?
1. Never, under any circumstances at all
2. On every upshift while you are moving
3. Only at a stop, to engage low gear
4. On every downshift when climbing hills
At what pressure do spring brakes normally apply automatically?
1. About 90 psi
2. About 60 psi
3. About 20 psi
4. About 120 psi
How should you chock a parked tractor-trailer?
1. Only in front of a steer tire
2. Under the fifth wheel plate
3. Front and back of a rear wheel
4. Behind the landing gear pads
When should you NOT engage the inter-axle differential lock?
1. On a gravel road at low speed
2. When starting on a wet ramp
3. Before a slippery stretch
4. While the wheels are spinning
Where is over-braking a combination most likely to cause a skid or jackknife?
1. At low speed in a yard
2. When the trailer is fully loaded
3. On wet roads or in curves
4. On dry, straight highway
What should be your main way of controlling speed on a long downgrade?
1. Engine braking
2. Fanning the brakes
3. Steady light braking
4. Coasting in neutral
How soon after moving off should you check your brakes?
1. After 1 km
2. Within about 15 m
3. At the first stop sign
4. Only before a downgrade
Why avoid using the differential lock when it is not needed?
1. It wears tires and strains axles
2. It disables the ABS
3. It raises the trailer height
4. It drains the air tanks
The trailer's rear wheels slide sideways. What should you do?
1. Release brakes, ease on throttle
2. Shift into neutral and coast to a stop
3. Brake harder with the foot valve
4. Apply the trailer hand valve hard
Which of these must never be used to hold a parked unit?
1. The trailer hand valve
2. The parking brake control
3. Wheel chocks
4. The spring brakes
Testing power-assisted hydraulic brakes, the pedal drops slightly and stops when you start the engine. What does it mean?
1. The fluid is leaking out
2. The brakes are out of adjustment
3. The master cylinder has failed
4. The power assist is working
What is balanced braking in a tractor-semitrailer?
1. Foot valve applies both units equally
2. Only the drive axles brake
3. The hand valve and pedal cancel out
4. The trailer brakes before the tractor
Your service brakes fail on a level road. What should you do first?
1. Pull the trailer supply valve at speed
2. Steer into the ditch
3. Shut off the engine
4. Downshift and use engine braking
What does the trailer hand valve let you do?
1. Park the combination safely
2. Raise the fifth wheel
3. Apply only the trailer brakes
4. Release the tractor spring brakes
On an air-brake tractor, when may you start moving after starting the engine?
1. After exactly five minutes
2. As soon as the engine is running
3. When the oil light comes on
4. Once the low-air warning has stopped

Controls, braking and jackknife control: key rules to remember

Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗

Starting the engine

Apply the parking brake, press the clutch and put the transmission in neutral before operating the starter.
Check the oil pressure gauge once the engine is running.
On air-brake vehicles, the air gauge must show enough pressure and the low-air buzzer and/or light must have stopped before you move.

Putting vehicle in motion

Release the clutch gradually while releasing the hand control valve or parking brake.
Test the brakes right after the vehicle starts moving, within about 15 m (50 ft).

Transmissions

Start moving in the lowest appropriate gear and apply power gradually with heavy loads on hills.
Do not shock-load the driveline by dropping the clutch, and do not let the clutch slip too much (it overheats).
On vehicles with a clutch brake, do not push the clutch to the floor when shifting while moving; floor it only at a stop to engage low gear quietly.

Inter-axle differential lock

Used on tandem rear axles; it has only two positions, lock and unlock, and is normally kept unlocked.
Lock it only when approaching conditions where wheels may slip; it then drives both axles equally.
Never engage it while the wheels are actually spinning; unnecessary use wears tires and strains axles.

Stopping and grades

Press steadily at the start of a stop and ease off as you slow; just before stopping, release slightly to avoid a jerk, then re-apply to hold.
Do not fan the brakes on dry pavement: it wastes air and on a long downgrade can drop pressure below what the brakes need.
On long downgrades use engine braking as the main speed control, ideally in the same gear you would use to climb that hill, chosen before starting down.
If the low air-pressure warning comes on, stop at once in the safest available place and fix the air loss.
If brakes fail on a level road, downshift and use the engine; for a shorter stop use the tractor and trailer emergency brakes, and do not drive again until repaired.
Some municipalities restrict engine braking; obey their signs.

Combination braking

With the foot valve, tractor and trailer brakes apply together at equal pressure; this is called balanced braking.
The trailer hand valve applies the trailer brakes alone; pulling it harder during a foot application can raise the trailer brake pressure.
Over-braking a combination on a wet or slippery surface or in a curve can cause a skid or jackknife.
If the tractor's rear wheels slide sideways (tractor jackknife), apply only the trailer brakes.
If the trailer's rear wheels slide sideways, release all brakes and gradually apply the accelerator.
Spring brakes apply automatically when system pressure drops below a set level, normally 60 psi (414 kPa).

Parking

Set the parking brakes and chock the rear wheels (front and back of a wheel) on one or both sides of the unit or trailer.
Never hold a parked unit with the trailer hand valve or the tractor protection valve.

Hydraulic brakes

With power assist: engine off, pump the pedal several times, apply moderate pressure, then start the engine; the pedal should drop slightly and stop.
If the pedal keeps dropping or does not drop at all, stop the engine and take the vehicle out of service for professional repair.
Without power assist: apply and hold moderate pressure; a steady drop means the vehicle must be taken out of service.

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