52 topics · Updated 2026-09-17
To test the park control valve, push the park control valve (yellow button) and pump the foot valve. Confirm the park control valve (yellow button) pops out at 20-45 PSI (138-311 kPa). After the test, reconnect both air lines to the trailer.
An air brake system uses air pressure from an engine-driven compressor sent through hoses, reservoirs and control valves to all foundation brakes. Different systems require different endorsements: full air brakes and air-over-hydraulic require a 'Q' endorsement or Class 1; air-actuated hydraulic (air assisted, all hydraulic foundation brakes) does NOT require a 'Q' endorsement.
You are not required to hold an air brake endorsement to operate a single motor vehicle registered as a farm vehicle. However, an air brake endorsement is required for a farm vehicle combination requiring a Class 1 licence. Proof of air brake qualification is needed when applying for Class 1 even for farm vehicles.
A 'Q' endorsement is placed on a licence when a driver completes an approved Alberta air brake course through an authorized organization. An 'S' endorsement allows Class 1, 2 or 4 holders to drive school buses transporting students after completing the School Bus Driver Improvement Program.
A bus is a commercial vehicle designed for carrying 11 or more persons including the driver. A semi-trailer has axles only near its rear, is supported at the front by the tractor, and connects via kingpin and fifth wheel. A truck tractor is a truck coupled to a semi-trailer by a fifth wheel.
Apply brakes with even pressure and ease off as the vehicle slows, releasing just before the stop to avoid jerk, then reapply to hold the vehicle stopped.
Avoid overusing brakes on downgrades; use engine compression and downshift before the hill. Test brakes before descending and respond to low air pressure warnings.
When approaching a crossing: slow down, shift to a lower gear (manual transmission) and test brakes; check traffic behind and stop gradually; stop no closer than five metres and no further than 15 metres from the nearest rail; roll down the window to hear a train; look carefully in each direction around obstructions; and set park brakes while waiting.
Before crossing, ensure there is enough room on the other side for the whole unit including overhang (a train is a metre wider than the rails on both sides). Use a gear that lets you cross without shifting, check signals again, and if lights begin to flash after starting, keep going rather than backing up. With multiple tracks there may be more than one train.
If your vehicle stalls or gets stuck on a crossing, get out immediately. If a train is coming, move away from the track toward the oncoming train to reduce chances of being struck by flying debris. Contact the railway company at its posted emergency number or call 911.
Do not cross unless you can see far enough in both directions to be sure no train is approaching. Be especially careful at crossings without gates, lights or bells. Even with active warning signals not indicating a train, still look and listen. Be cautious at uncontrolled rural crossings at night where a train may appear as a dark object against a dark road.
Know your vehicle length, overhang and available space on the other side. When a STOP sign faces you across the tracks, check the room between the tracks and the sign to ensure you can fully clear. If space is insufficient and your vehicle would overhang the tracks, visually and audibly confirm no oncoming train before proceeding. Do not block a crossing for more than 20 seconds.
When approaching a crossing, slow down, shift to a lower gear (manual), and test brakes. Check traffic behind you and stop gradually. Stop between five and fifteen metres from the nearest rail. Roll down the window and reduce noise to better hear a train, look carefully in each direction around obstructions, and set park brakes while waiting.
Before crossing, ensure there is enough room on the other side for the whole unit including overhang (a train is a metre wider than the rails on both sides). Use a gear that lets you cross without shifting, check signals once more, and if lights begin flashing after starting, keep going rather than backing up. Remember multiple tracks may carry multiple trains.
Crossing railway tracks is especially hazardous for large vehicles because longer vehicles need more time to clear a crossing, heavier vehicles need more time and room to stop, and larger vehicles are more likely to derail a train in a collision.
Pay extra attention at rural railway crossings because approach grades may be steeper, snow banks higher, brush and trees more common, there tend to be fewer automated warning systems, and the grade crossing may be rough or uneven.
Crossing railway tracks is especially hazardous for large vehicles because longer vehicles need more time to clear a crossing, heavier vehicles need more room to stop, and larger vehicles are more likely to derail a train in a collision.
Do not attempt to cross unless you can see far enough in both directions to be sure no train is approaching. Be especially careful at crossings without gates, lights or bells. Even with active signals showing no train, look and listen. Be cautious at uncontrolled rural crossings at night, where a train may appear as a dark object against a dark background.
Pay extra attention at rural railway crossings because approach grades may be steeper, snow banks higher, brush and trees more common, there tend to be fewer automated warning systems, and the grade crossing may be rough or uneven.
When uncoupling air lines, hold a hand over the supply coupler to protect from air pressure release and potential debris. When coupling after the park control valve pops out, inspect the glad hand couplers before connecting, connect them properly, and confirm correct connection. Confirm air lines to the trailer are properly suspended and will not catch as the trailer turns.
After completing the pre-trip, restart the engine to maintain air pressure and activate the automatic slack adjuster by applying two full service brake applications. Applications must be done with air pressure in the normal operating range, allowing one second intervals to account for brake lag. Confirm proper brake adjustment by pulling the slack adjusters on both brakes of one axle, commonly the rear trailer axle.
Apply brakes with even pressure and ease off as the vehicle slows. Just before stopping, release the brakes to avoid a jerk or rebound, then reapply pressure to hold the vehicle when stopped. Never pump air brakes as this causes loss of air pressure.
Avoid using brakes too much going downhill. Downshift before going over the top of the hill and use engine compression to control speed on steep grades. Pumping brakes on a long downhill grade may leave insufficient air pressure.
If a low air pressure warning occurs, stop as soon as possible in a safe place and increase air pressure before continuing. Before descending a hill, test the brakes by checking the gauge and applying brakes; do not proceed if there is abnormal pressure loss.
Overuse of the trailer hand valve, especially on steep hills, may cause trailer brake failure and greater wear on trailer brakes than tractor brakes. Using only the hand valve is not recommended as it causes unbalanced braking that could cause a jackknife.
A driver must not pull any trailer weighing more than 2,300 kg that is not equipped with brakes controlled by the driver.
When approaching a crossing: slow down, downshift (manual transmission), and test brakes. Check for traffic behind and stop gradually. Stop no closer than five metres (16 feet) and no further than 15 metres (49 feet) from the nearest rail. Roll down the window and reduce noise to hear a train. Look carefully both directions around obstructions. Apply the park brakes while waiting.
Before resuming: ensure enough room on the other side for the whole unit to clear, including overhang (a train is a metre wider than the rails on both sides). Use a gear that lets you cross without shifting. Recheck crossing signals. If lights start flashing after you begin, keep going—it's safer than backing up. With multiple tracks, expect more than one train.
If your vehicle stalls or gets stuck on a crossing, get out immediately. If a train is coming, move away from the track toward the oncoming train to reduce chances of being struck by flying debris if the train hits your vehicle. Contact the railway company (posted emergency number) or call 911.
Know your vehicle length, overhang, and available space on the far side. When a STOP sign faces you on the opposite side, ensure enough room to fully clear the tracks. If space is insufficient and you'd overhang the tracks, visually and audibly confirm no oncoming train first. Do not block the railway crossing for more than 20 seconds.
A controlled crossing has a flag person, stop sign, crossing gate, or an electric/mechanical signalling device—all vehicles must stop if signalled. Some vehicles must stop at ALL uncontrolled crossings: school buses, vehicles carrying explosives, and vehicles designated for flammable liquids or gas (loaded or empty). Obey any police officer or railway flag person, and be aware of municipal bylaws.
Crossing railway tracks is especially hazardous for large vehicles because longer vehicles need more time and distance to clear a crossing, heavier vehicles need more room to stop, and larger vehicles are more likely to derail a train in a collision.
Do not cross unless you can see far enough both directions to confirm no train is approaching. Be extra careful at crossings without gates, lights, or bells. Even with active warning signals showing no train, look and listen. At night on uncontrolled rural crossings, a train may appear as a dark object against a dark road.
Pay extra attention at rural crossings because approach grades may be steeper, snow banks higher, brush and trees more common, there tend to be fewer automated warning systems, and the grade crossing may be rough or uneven.
Drivers are always responsible for the performance of their brake systems. It is the driver's responsibility to ensure brakes are working correctly. Drivers must understand how the system works, perform effective vehicle inspections, ensure brakes are correctly adjusted, use brakes properly, and know how the vehicle reacts during various circuit failures.
Compressed air is air pressed into a smaller space than it normally occupies; the greater the compression, the greater the resistance, which multiplies over surface area to create power to apply brakes. Pressure is measured in PSI (pounds per square inch) or kPa (kilopascals). Key conversion: 1 PSI = 6.895 kPa; 1 kPa = 0.145 PSI; 1 atmosphere = 14.5 PSI = 100 kPa = 1 bar.
Every jurisdiction in Canada except Nunavut requires drivers of air brake equipped vehicles to have an air brake endorsement. Air brakes differ from hydraulic in pedal feel, vehicle reaction, more gauges and controls, and require more driver involvement to ensure safe operation.
Other than a Class 1 licence, the air brake 'Q' endorsement is independent of the class of licence held (marked as code Q on Classes 2 through 7). The Class 1 licence includes the air brake endorsement but holders must still pass the Alberta Air Brake Program. Drivers of two-axle single motor vehicles registered as farm vehicles do not require an air brake Q endorsement.
Compressed air is air pressed into a smaller space than it normally occupies; the greater the compression the greater its resistance and power. Air pressure exhausts at points usually located under the vehicle. Injury is a concern only when doing maintenance under the vehicle. Use caution draining tanks or removing fittings, and drain the system before maintenance.
Drivers are always responsible for the performance of their brake systems. They must understand how the brake system works, perform effective vehicle inspections, ensure brakes are correctly adjusted, use brakes properly, and know how the vehicle reacts during various circuit failures.
Air brakes generate greater power than hydraulic brakes, are tolerant to small leaks (systems have compressors to pump more air, whereas hydraulic leaks can lead to brake failure), allow easier coupling of multiple combinations, and are proven capable, becoming more common in RVs and smaller trucks.
Air pressure is measured in pounds per square inch (PSI) traditionally, or kilopascals (kPa) increasingly used by OEMs. European vehicles use bars (equivalent to one atmosphere). Key conversion: 1 PSI = 6.895 kPa, 1 kPa = 0.145 PSI, 1 atmosphere = 14.5 PSI = 100 kPa = 1 bar.
Every jurisdiction in Canada, except Nunavut, requires drivers of air brake equipped vehicles to have an air brake endorsement. The 'Q' endorsement is marked as a code on Classes 2-7. The Class 1 licence includes the air brake endorsement, but the holder must still pass the Alberta Air Brake Program. Two-axle single motor vehicles registered as farm vehicles do not require the 'Q' endorsement.
The supply circuit is colour-coded blue. Service brake circuits are green (primary, drive axles) and red (secondary, steering axle). The park/emergency circuit is orange. Solid colours are filled from the compressor and stay filled; dashed colours are sections controlled by the driver. Trailer air lines are red and blue.
Compressed air can be hazardous. Control and quick release valves exhaust forcefully when service brakes are released or park brakes applied. Air dryers purge powerfully. When disconnecting charged air lines, turn your head away and cover the coupler with a free hand. Drain tanks before doing air system work and wear PPE.
The traditional standard is pounds per square inch (PSI); OEMs may use kilopascals (kPa), which is becoming more common. European vehicles use bars (equivalent to an atmosphere). Key conversions: 1 PSI = 6.895 kPa; 1 atmosphere = 14.5 PSI = 100 kPa = 1 bar. All vehicles with air brakes have air pressure gauges in the dash.
The supply circuit is blue. Red and green circuits operate the service brakes on the tractor. The park circuit is orange. Solid colours are filled from the compressor and stay filled; dashed colours are sections controlled by the driver during applications or release. Trailer air lines are red and blue to reflect the truck air lines. Drivers are always responsible for the performance of their brake systems.
Compressed air can be dangerous. Points where air pressure exhausts are usually located under the vehicle. Personal injury is not a concern unless air pressure exhausts while doing maintenance under the vehicle. Use caution when draining air pressure from tanks or removing fittings and hoses, and drain the system before doing any maintenance.
Drivers are always responsible for the performance of their brake systems. They must understand how the brake system works, perform effective vehicle inspections, ensure brakes are correctly adjusted, use the brakes properly, and know how the vehicle reacts during various circuit failures.
Most air brake equipped vehicles have readily accessible air tanks and chambers, though some vehicle bodies (fire trucks, motor homes) make them hard to see. All vehicles with air brakes have air pressure gauges in the dash.
Other than the Class 1 licence, the air brake Q endorsement is independent of the class of licence held and is marked as code Q on Classes 2 through 7. The Class 1 licence includes the air brake endorsement. Holders of a Class 1 licence must still pass the Alberta Air Brake Program. Drivers of two-axle single motor vehicles registered as farm vehicles do not require the Q endorsement.
The air brake schematic uses colour coding: the supply circuit is blue; service brake circuits use green (primary, drive axles) and red (secondary, steering axle); the park/emergency circuit is orange. Solid colours are filled from the compressor and stay filled; dashed colours are sections controlled by the driver during applications. Trailer air lines are red and blue to reflect truck air lines.
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