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Commercial Drivers Licence Online Practice Test - Exam 4
Date :
20 / 10 / 2026
Q
1
)
The air storage tanks are used to hold compressed air.
TRUE
FALSE
Dont Know
None of the above
Q
2
)
Modern air brake systems combines three different systems. The are the service brakes, the parking brakes and the:
S-cam brakes.
Drum brakes.
Foot brakes.
Emergency brakes.
Q
3
)
What can you check to see if the spring brakes come on automatically?
Step on and off the brake‚ with the engine off‚ the parking brake knob should pop out when air pressure falls between 20-40 psi.
Get under the vehicle and pull on the spring brakes.
Turn on the engine and pump the brake pedal down to the floor.
None of the above
Q
4
)
You should know that your brakes are fading when:
Pressure on the brake pedal is released and speed increases.
You have to push harder on the brake pedal to control your speed on a downgrade.
The brake feels spongy when pressure is applied.
Less pressure is needed on the brake pedal for each stop.
Q
5
)
The S-cam forces the brake shoes away from one another and presses them against the inside of the brake drum. It is called the S-cam because:
It is shaped like the letter Z.
It is shaped like the letter N.
It is shaped like the letter S.
None of the above
Q
6
)
To make an emergency stop with air brakes, using the stab braking method, you should:
Pump the brake pedal rapidly and lightly.
Brake hard until the wheels lock‚ and then get off the brakes for as much time as the wheels were locked.
Brake as hard as you can‚ get off the brakes when the wheels lock‚ get back on the brakes when the wheels start rolling again.
Press hard on the brake pedal and apply full hand valve until you stop.
Q
7
)
In air brake vehicles, the parking brakes should be used:
To hold your speed when going downhill.
Whenever the vehicle is parked.
As little as possible.
Only during pre and post trip inspections.
Q
8
)
The use of brakes on a long steep downgrade is only a supplement to the braking effect of the engine.
TRUE
FALSE
Dont Know
None of the above
Q
9
)
Of the choices below, the first thing to do when a low air pressure warning comes on is:
Open the air supply control valve.
Adjust the brake pedal for more travel.
Stop and safely park as soon as possible.
Up-shift.
Q
10
)
What is another name for controlled braking?
Steady braking
Squeeze braking
Hard braking
None of the above
Q
11
)
The brake system that applies and releases the brakes when the driver uses the brake pedal is the:
Service brake system.
Emergency brake system.
Parking brake system.
None of the above.
Q
12
)
If you must make an emergency stop, you should brake so that you:
Use the full power of the brakes and lock them.
Can steer hard while braking hard.
Stay in a straight line and can steer.
Use the hand brake first.
Q
13
)
The application pressure gauge shows the driver how much pressure:
Has been used on the trip.
Is in the air tanks.
None of these.
Is being applied to the brakes.
Q
14
)
What factors can cause brakes to fade or fail?
Not pressing the brake pedal hard enough.
Over heating‚ low air pressure‚ and not relying on the engine braking effect.
Not taking your foot off the accelerator pedal.
None of the above
Q
15
)
If your vehicle has an alcohol evaporator, every day during cold weather you should:
Clean the air filter with alcohol.
Check and fill the alcohol level.
Change the alcohol from a new bottle.
Check the oil for alcohol content.
Q
16
)
The service brake applies and releases:
The parking brake when you use the parking brake control.
The brake when you use the brake pedal during normal driving.
In the event of an emergency.
None of the above
Q
17
)
The brake pedal in an air brake system:
Is to be used as a footrest during normal driving.
Controls the speed of the air compressor.
Controls the air pressure applied to put on the brakes.
Is connected to slack adjusters by a series of rods and linkages.
Q
18
)
Why drain water from the compressed air tanks?
To keep from fouling the air compressor oil.
Water can freeze in cold weather and cause brake failure.
The low boiling point of water reduces braking power.
Water over cools the compressor.
Q
19
)
What can legally hold a parking or emergency brake in position for a truck, truck tractor or bus?
Fluid pressure
Air pressure
Spring pressure
Any of the above
Q
20
)
What are the maximum leakage rates?
Less than four psi in one minute for single vehicles and less than eight psi in one minute for combination vehicles.
Less than two psi in one minute for single vehicles and less than three psi in one minute for combination vehicles.
Less than six psi for all vehicles.
None of the above
Minumum pass for the test is 75%
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Commercial Drivers Licence
Commercial Driver Licence Test 1
Commercial Driver Licence Test 2
Commercial Driver Licence Test 3
Commercial Driver Licence Test 4
Commercial Driver Licence Test 5
Commercial Driver Licence Test 6
Commercial Driver Licence Test 7
Commercial Driver Licence Test 8
