Alberta Air Brakes Exam Prep
Practice Test

A. To connect the electrical system between tractor and trailer

B. To couple the air supply and service lines between tractor and trailer ✓

C. To lock the fifth wheel in place

D. To equalize air pressure across all axles

Correct — B. Glad hands are the quick-connect coupling devices that join the tractor's air lines to the trailer's air lines. They consist of two half-circles that lock together when twisted, creating an airtight seal for both the supply (emergency) line and the service (control) line. Without properly connected glad hands, the trailer brakes cannot receive air pressure.

A. 80 psi

B. 90 psi ✓

C. 100 psi

D. 110 psi

Correct — B. The governor cuts in (activates the compressor) when system pressure drops to approximately 90 psi. The compressor then pumps air until pressure reaches the cut-out level of about 135 psi. This on/off cycling maintains air pressure within the safe operating range for braking.

A. Red

B. Blue ✓

C. Yellow

D. Green

Correct — B. The service (control) line glad hand is color-coded blue, while the supply (emergency) line glad hand is coded red. This standardized color coding prevents cross-connection, which could cause trailer brake failure or unintended spring brake application.

A. 1 psi per minute

B. 2 psi per minute ✓

C. 3 psi per minute

D. 5 psi per minute

Correct — B. For a single vehicle with brakes released, acceptable air pressure loss must not exceed 2 psi per minute. With brakes applied, the acceptable loss increases to 3 psi per minute. Losses exceeding these limits indicate leaks in the system that must be repaired before the vehicle is driven.

A. They release automatically

B. They apply automatically ✓

C. They cycle on and off

D. They lock in the current position

Correct — B. When system air pressure falls to approximately 45 psi, the spring park brakes apply automatically. The coil springs inside the spring brake chamber are held compressed by air pressure; when that pressure drops sufficiently, the springs expand and apply the brakes regardless of driver input — a critical fail-safe design.

A. The relay valve

B. The slack adjuster

C. The brake chamber ✓

D. The air dryer

Correct — C. The brake chamber converts air pressure into mechanical force. When compressed air enters the chamber, it pushes against a diaphragm, which moves the push rod outward. The push rod then activates the slack adjuster and S-cam mechanism to press the brake shoes against the drum.

A. Type 20 standard chamber

B. Piggyback or combination chamber ✓

C. Type 30 service chamber

D. Diaphragm relay chamber

Correct — B. A piggyback (combination or spring-brake) chamber combines two separate chambers in one unit. The front section is a standard service chamber that applies brakes using air pressure; the rear section houses the coil spring that applies the parking/emergency brake when air pressure is released. This design is common on drive and trailer axles.

A. It doubles the braking force in emergency situations

B. It allows the higher of two air pressure sources to pass through to activate a function ✓

C. It prevents air from returning to the compressor

D. It balances pressure between the front and rear brake circuits

Correct — B. A double check valve allows the higher pressure from either of two air sources to pass through to supply a common function. It is commonly used in the spring brake release circuit — whichever source (primary or secondary) has higher pressure is automatically selected, ensuring parking brakes can be released if either circuit has adequate pressure.