The Alberta Air Brake Program
Drivers of Class 1, 2, 3, 4 or 5 vehicles need the Q endorsement before they drive a vehicle with air brakes. A Class 1 licence cannot be issued without it. Single-motor farm vehicles are exempt, but a farm combination that needs a Class 1 licence is not, and Class 1 applicants must show proof of air brake training. The program began in November 1990.
- Classroom training: at least 6.5 hours at a licensed driver training school. You receive the *Air Brake Manual: A Guide for Students*.
- Practical training: a 15-minute instructor demonstration, then you practise the air brake pre-trip inspection twice.
- Practical assessment: a one-on-one assessment on the Air Brake Practical Test form, with a 15-minute time limit. When you pass, you get a Notice of Air Brake Program Completion.
- Knowledge test: take your Notice to any Alberta registry agent and write the test.
The knowledge test
- 30 multiple-choice questions. You need 25 correct.
- The test ends automatically after 6 wrong answers.
- It is electronic and in English only. There is no time limit and no limit on attempts.
- You need a valid, unsuspended Alberta licence.
- If you fail, you retest on a different day.
If you fail the practical assessment, you get one reassessment on a different day before more training is needed. No road test is required, and the endorsement has no renewal requirement. When you pass, the Q endorsement appears on your licence card. Some qualified mechanics and inspection technicians may challenge the tests without the training; Examinations and Licensing confirms who is eligible.
How an air brake system works
The main parts of a basic air brake system.
- Air compressor, driven by the engine.
- Governor, which tells the compressor when to cut in and cut out.
- Air tanks, which store the compressed air.
- Drain valve on each tank, to remove water and oil.
- Foot valve (brake pedal), which sends air to the brakes.
- Brake chamber, where air pushes a diaphragm and push rod.
- Slack adjuster, which turns the brake camshaft.
- Brake drum, where the shoes press when the S-cam turns.
The compressor fills the tanks. When you press the pedal, the foot valve sends air to the brake chambers. Each chamber pushes a rod that turns a slack adjuster and camshaft. In an S-cam brake, the S-shaped cam forces the shoes against the drum. A safety valve lets out air if tank pressure gets too high.
Spring brakes are applied by strong springs and held off by air. If air pressure is lost, the springs apply the brakes. Use the spring brakes to park, because service brakes depend on air that can leak away. A dual system has two circuits, so if one fails the other can still stop the vehicle.
Moisture in the air can freeze in cold weather and block lines and valves. Drain the tanks to remove water and oil. The tractor protection valve keeps the tractor's air if the trailer lines break. The supply (emergency) line is usually red and the service line blue.
Air brake trip test figures
The Alberta Commercial Driver's Guide lists these key figures for the air brake trip test. Park on level ground and chock the wheels first.
| Check | What should happen |
|---|---|
| Low air warning | On by 60 psi as pressure drops |
| Park control valve | Pops out between 20 and 45 psi |
| Compressor build-up | From 50 to 90 psi within 3 minutes |
| Governor cut-out | Between 120 and 135 psi |
| Governor cut-in | About 20 to 25 psi below cut-out |
| Applied leakage (2 minutes, full application) | No more than 4 psi for a power unit, plus 2 psi for each trailer |
Brake adjustment is checked by measuring push rod stroke with the brakes applied. Too much stroke means the brake is out of adjustment.
Using air brakes safely
- Perception and reaction each take about 0.75 seconds. Air brake lag adds about 0.4 seconds, so leave more room ahead than a car would.
- Brake with steady pressure and ease off as you slow. Do not pump air brakes; it wastes air.
- Downshift before the top of a hill and test your brakes. Do not go down if air pressure drops abnormally.
- Do not rely on the trailer hand valve alone. Using only the trailer brakes can cause a jackknife.
- Doubling your speed makes your stopping distance about four times as long.
Brake fade is a loss of braking power when brakes get too hot. Use a low gear and engine braking on long grades to keep the brakes cool. If the low air warning comes on, stop safely and find out why. If your spring brakes come on suddenly while driving, you have most likely lost a lot of air pressure.
Doing the trip test step by step
Your course teaches the full air brake pre-trip inspection. In simple terms, the checks in the Commercial Driver's Guide work like this:
- Park on level ground and chock the wheels with chocks at least 15 cm by 15 cm.
- Start the engine and build the air. Pressure should rise from 50 to 90 psi within 3 minutes.
- Watch the gauge as the governor cuts out. It should be between 120 and 135 psi.
- With the engine running, fan the brake pedal to lower the pressure. The governor should cut in about 20 to 25 psi below the cut-out pressure.
- Keep lowering the pressure. The low air warning should be on by 60 psi.
- Keep going until the park control valve pops out, between 20 and 45 psi.
- Rebuild the pressure and do the applied leakage check: with a full brake application, a power unit should lose no more than 4 psi in 2 minutes, plus 2 psi for each trailer.
As you work, say what you are checking and what result you expect. That shows the assessor you understand the reason for each step, not just the order.
Key numbers at a glance
| What | Number |
|---|---|
| Classroom training | At least 6.5 hours |
| Instructor demonstration | 15 minutes |
| Practice pre-trips | Two |
| Practical assessment time limit | 15 minutes |
| Knowledge test | 30 questions, 25 to pass, ends after 6 wrong |
| Low air warning on by | 60 psi |
| Park control valve pops out | 20 to 45 psi |
| Build-up | 50 to 90 psi within 3 minutes |
| Governor cut-out | 120 to 135 psi |
| Brake lag | About 0.4 seconds |
Common mistakes to avoid
- Pumping the brakes. Each pump uses air. Use steady pressure instead.
- Parking with the trailer hand valve. Service air can leak away. Park with the spring brakes.
- Ignoring the low air warning. It means you are losing braking ability. Stop safely and find the cause.
- Not draining the tanks. Water in the system can freeze and block lines and valves.
- Riding the brakes downhill. Hot brakes fade. Use a lower gear chosen before the hill.
- Following too closely. Air brake lag adds to your stopping distance, so leave more room.
On test day
Take your Notice of Air Brake Program Completion and your valid Alberta licence to any registry agent. A government fee and service charge apply. The test is on a computer, in English only. Read each question slowly; there is no time limit. If you do not pass, you can try again on a different day, and there is no limit on attempts. When you pass, the Q endorsement is added to your licence card, and it never needs renewing.
How far you travel before the brakes work
Before your brakes start to slow you, three things happen. You see the danger (perception, about 3/4 of a second), you move your foot to the pedal (reaction, about 3/4 of a second), and the air travels through the lines to the brakes (lag, about 4/10 of a second). That adds up to about 1.9 seconds.
At 100 km/h, a vehicle covers about 28 metres every second. So in those 1.9 seconds it travels about 53 metres before the brakes even begin to work. Only then does the braking distance start. This is why heavy vehicles need a long following distance, and why speed matters so much: doubling your speed needs about four times the stopping power.
A simple study plan
- Read this guide once from start to finish, without trying to memorise everything.
- Read the matching chapters of the Air Brake Manual: A Guide for Students. Mark every number, limit and time you find.
- Take the first practice test. Write down each question you get wrong and look up the rule.
- Make a one-page list of key numbers, and test yourself on it every day.
- Take the other practice tests until you score at least 80% every time.
- Finish with the mock exam, timed if the real test is timed.
Short, regular study works better than one long session. Twenty or thirty minutes a day for two weeks will help you remember more than one long night before the test. Read each question to the end before you look at the answers, and watch for words like minimum, maximum, before and after.