B.C. Air Brake Practice Test 2026: Practice test 2

Practice test 2 of 2 for the B.C. Air Brake Practice Test: 35 more questions with answers and explanations.

Commercial vehicle
British Columbia
60 questions
Checked October 10, 2026

Question 1 of 35
What does the brake pedal (foot valve) do in an air brake system?
- It pumps air into the tanks
- It releases air from the tires
- It switches the compressor on
- It sends air from the tanks to the brake chambers
Show answer
Answer: D. It sends air from the tanks to the brake chambers
Pressing the pedal opens the foot valve, which sends air to the brake chambers.
Question 2 of 35
When air enters a brake chamber, what moves?
- A diaphragm pushes the push rod out
- The brake drum starts to spin faster
- The governor cuts out the compressor
- The tank drain valve opens
Show answer
Answer: A. A diaphragm pushes the push rod out
Air pressure pushes the diaphragm, which pushes the rod that turns the slack adjuster.
Question 3 of 35
What connects the push rod to the brake camshaft?
- The gladhand
- The foot valve
- The slack adjuster
- The governor
Show answer
Answer: C. The slack adjuster
The slack adjuster links the push rod to the camshaft and adds leverage.
Question 4 of 35
Why must water be drained from air tanks?
- Water can freeze and block valves and lines
- Water makes the brakes stronger
- Water cools the engine
- Water is needed for the brakes to work
Show answer
Answer: A. Water can freeze and block valves and lines
Water and oil collect in the tanks. In cold weather, water can freeze and stop the system working.
Question 5 of 35
What protects the air tanks from too much pressure?
- The safety valve
- The slack adjuster
- The low air warning
- The brake drum
Show answer
Answer: A. The safety valve
If pressure gets too high, the safety valve lets air out.
Question 6 of 35
What must a low air pressure warning do?
- Warn you with a light, buzzer or both when pressure is low
- Stop the engine so the vehicle cannot move
- Fill the air tanks from a reserve supply
- Turn on the hazard lights for other drivers
Show answer
Answer: A. Warn you with a light, buzzer or both when pressure is low
The warning tells you pressure is getting low so you can stop safely before the spring brakes apply.
Question 7 of 35
While driving, your low air pressure light and buzzer come on. What is the right action?
- Pull over and stop safely as soon as possible
- Speed up to reach the next town sooner
- Pump the brake pedal to build up air
- Keep driving to the end of your shift
Show answer
Answer: A. Pull over and stop safely as soon as possible
Low air means you are losing braking ability. Stop safely and find the cause.
Question 8 of 35
How are spring brakes applied?
- By powerful springs when air pressure is released
- By the driver pulling a cable by hand
- By hydraulic fluid from a master cylinder
- By air pressure pushing on a diaphragm
Show answer
Answer: A. By powerful springs when air pressure is released
Spring brakes are held off by air. When air is released, or lost, the springs apply the brakes.
Question 9 of 35
Why are spring brakes used for parking?
- They are the only brakes fitted to the trailer
- They hold mechanically, without needing air in the system
- They are stronger only while the engine runs
- They use less fuel than the service brakes
Show answer
Answer: B. They hold mechanically, without needing air in the system
Service brakes rely on air pressure, which can leak away. Spring brakes hold with spring force.
Question 10 of 35
What happens to the spring brakes if the air system loses all its pressure?
- They apply
- They stay exactly as they were
- They switch to hydraulic power
- They release
Show answer
Answer: A. They apply
Loss of air pressure lets the springs apply the brakes. This is a safety feature.
Question 11 of 35
Why is a spring brake chamber dangerous to open?
- It contains hot oil under pressure
- Opening it cancels your licence
- It has no parts that can be serviced
- The spring is under great force and could injure you
Show answer
Answer: D. The spring is under great force and could injure you
The spring in the chamber is under great force. Only trained people with the right tools should service it.
Question 12 of 35
What is the main advantage of a dual air brake system?
- It works even with no air at all
- It does not need an air compressor
- If one circuit loses air, the other can still apply brakes
- Its brakes never need to be adjusted
Show answer
Answer: C. If one circuit loses air, the other can still apply brakes
Two separate circuits mean a failure in one still leaves braking from the other.
Question 13 of 35
On a tractor-trailer, what colour is the gladhand for the service (control) line?
- Red
- Yellow
- Black
- Blue
Show answer
Answer: D. Blue
The service line is usually blue, and the supply (emergency) line is red.
Question 14 of 35
What does the tractor protection system do if the trailer breaks away?
- Keeps the tractor's air, while the trailer's spring brakes apply
- It speeds the tractor up to get clear of the trailer
- It turns on the trailer lights to warn others
- It releases all of the tractor's brakes
Show answer
Answer: A. Keeps the tractor's air, while the trailer's spring brakes apply
The tractor keeps its air supply, and the trailer brakes apply when its air is lost.
Question 15 of 35
How is brake adjustment checked on S-cam brakes?
- By listening to the brakes while driving slowly
- By checking the tire pressure on each axle
- By measuring push rod stroke with the brakes fully applied
- By feeling how hot each drum is after a trip
Show answer
Answer: C. By measuring push rod stroke with the brakes fully applied
Measure how far the push rod moves on a full application. Too much stroke means the brake is out of adjustment.
Question 16 of 35
What does too much push rod stroke mean?
- The brake is working perfectly
- The governor is set too low
- The brake is out of adjustment
- The tank is too full
Show answer
Answer: C. The brake is out of adjustment
Excess push rod travel means the brake is out of adjustment and will not give full braking force.
Question 17 of 35
In ICBC's guide, what does brake fade mean?
- The low air warning turning itself off
- Rust building up on the drums
- A loss of braking power when the brakes overheat
- The brake light bulb burning out
Show answer
Answer: C. A loss of braking power when the brakes overheat
Overheated brakes lose effectiveness. Keep speed down and use a lower gear and retarder on hills.
Question 18 of 35
How should you apply air brakes for a normal stop?
- Pump the pedal quickly to build air
- Use only the trailer hand valve
- Smoothly and steadily, easing off as you slow
- Press as hard as you can every time
Show answer
Answer: C. Smoothly and steadily, easing off as you slow
Smooth, steady pressure stops the vehicle without wasting air or locking wheels.
Question 19 of 35
Why should you avoid fanning (pumping) air brakes?
- It wastes air and lowers the pressure in the system
- It drains fuel from the tank
- It makes the brakes far too strong
- It overheats the engine and compressor
Show answer
Answer: A. It wastes air and lowers the pressure in the system
Each pump uses air. Fanning the brakes can drop pressure quickly.
Question 20 of 35
What should you check on the compressor during the air brake inspection?
- The colour and make of the compressor
- That a belt-driven compressor's belt is in good shape and tight
- The fuel level inside the compressor
- The compressor's radio and wiring connection
Show answer
Answer: B. That a belt-driven compressor's belt is in good shape and tight
A loose or worn belt can stop the compressor from building air.
Question 21 of 35
During an air brake check, what should happen when you reduce the air pressure by fanning the brakes?
- The engine should stop when pressure falls
- The spring brakes should apply before the warning comes on
- The low air warning should come on before the spring brakes apply
- Nothing should happen until the tanks are empty
Show answer
Answer: C. The low air warning should come on before the spring brakes apply
The warning must activate before pressure falls low enough for the spring brakes to apply.
Question 22 of 35
What should you watch on the gauge while the engine builds air?
- That pressure drops while the engine runs
- That the fuel gauge rises with the air pressure
- That the needle stays at zero until you drive
- Steady pressure build-up and cut-out at the right pressure
Show answer
Answer: D. Steady pressure build-up and cut-out at the right pressure
Pressure should build at a normal rate and the governor should stop the compressor at the cut-out pressure.
Question 23 of 35
Why do you check for air leaks with the brakes applied?
- Leaks drain air quickly just when you need the brakes
- To test that the horn works on air
- To warm up the engine before driving
- To check the tire pressure on each wheel
Show answer
Answer: A. Leaks drain air quickly just when you need the brakes
Leaks reduce the air available for braking, and they get worse when the system is under pressure.
Question 24 of 35
Before testing air brakes on the road, how should you test them at low speed?
- Do not test them on the road at all
- Brake at low speed and check the vehicle stops straight
- Test only the parking brake while moving
- Test them only at highway speed
Show answer
Answer: B. Brake at low speed and check the vehicle stops straight
A low-speed test shows if the brakes work and if the vehicle pulls to one side.
Question 25 of 35
What is the purpose of an air dryer?
- To heat the brake drums in winter
- To dry the inside of the cab in wet weather
- To clean the windshield with warm air
- To remove moisture before the air reaches the tanks
Show answer
Answer: D. To remove moisture before the air reaches the tanks
An air dryer removes water from the compressed air, which helps prevent freezing and corrosion.
Question 26 of 35
Before you drive, the air gauge shows low pressure. What should you do?
- Drive off and let it build while moving
- Drain the tanks and start again
- Let the pressure build to normal before moving
- Release the spring brakes by hand
Show answer
Answer: C. Let the pressure build to normal before moving
Do not move until the air pressure has built up and the low air warning has gone off.
Question 27 of 35
Why must you not apply the service brakes hard while the spring brakes are on?
- Because it is the best way to park on a steep hill
- Because it cools the brakes far too quickly
- Because it uses no air at all from the tanks
- The combined forces can overload and damage brake parts
Show answer
Answer: D. The combined forces can overload and damage brake parts
Applying full service air on top of applied spring brakes can over-stress the brake parts.
Question 28 of 35
You park on a hill with an air-brake truck. What should you do?
- Leave the engine running so air keeps building
- Hold the service brake down with a stick
- Use only the trailer hand valve to hold it
- Set the spring brakes and use wheel chocks if needed
Show answer
Answer: D. Set the spring brakes and use wheel chocks if needed
Set the parking (spring) brakes and chock the wheels when needed. Never rely on air pressure to hold a parked vehicle.
Question 29 of 35
Where do you apply to take the air brake knowledge test in B.C.?
- At your trucking company
- At a police station
- At a driver licensing office
- At a weigh scale
Show answer
Answer: C. At a driver licensing office
Apply at a driver licensing office with your ID and pay the knowledge test fee.
Question 30 of 35
In an emergency, how quickly can a tractor-trailer stop from 100 km/h with good brakes?
- In as little as about 1 second
- In as little as about 7 seconds
- In no less than about 30 seconds
- In no less than about 2 minutes
Show answer
Answer: B. In as little as about 7 seconds
A tractor-trailer may stop from 100 km/h in as little as 7 seconds, which takes huge braking force from every brake.
Question 31 of 35
What does the parking brake control knob usually look like?
- A green toggle switch
- A blue, square lever
- A yellow, diamond-shaped push-pull knob
- A red, round push button
Show answer
Answer: C. A yellow, diamond-shaped push-pull knob
The parking (spring) brake control is a yellow, diamond-shaped push-pull knob.
Question 32 of 35
In the cab, how can you recognise the trailer supply control?
- A black dial
- A yellow, diamond-shaped knob
- A blue, square knob
- A red, eight-sided push-pull knob
Show answer
Answer: D. A red, eight-sided push-pull knob
The trailer supply (tractor protection) control is a red, eight-sided knob.
Question 33 of 35
How does a retarder help the air brakes?
- It adds extra air to the tanks while you drive
- It makes the service brakes apply faster
- It adjusts the slack adjusters automatically
- It slows you without the service brakes, so they stay cool
Show answer
Answer: D. It slows you without the service brakes, so they stay cool
Retarders such as engine and exhaust brakes reduce the work, heat and wear on the service brakes.
Question 34 of 35
Which low air warning device is a mechanical arm that drops into view?
- A wig wag
- A slack adjuster
- A governor
- A gladhand
Show answer
Answer: A. A wig wag
A wig wag is a mechanical warning arm that drops into view when pressure falls too low.
Question 35 of 35
Which retarder type uses the engine to slow the vehicle?
- An electric driveline retarder
- An engine retarder
- A spring brake
- A trailer hand valve
Show answer
Answer: B. An engine retarder
Engine retarders use the engine to slow the vehicle. Others work in the exhaust or the driveline.

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