Air brakes consists of three separate braking systems: the service brake system, the parking brake system, and the emergency brake system.

If the low pressure warning signal activates while you are driving, it is important that you safely exit the roadway as soon as possible and park your vehicle. If the air pressure gets too low, the brakes will no longer work well enough for you to stop safely.

A dolly equipped with an Anti-Lock Braking System (ABS) is required to have a yellow malfunction lamp located on its left side.

If a tractor is equipped with an Anti-Lock Braking System (ABS) but the trailer is not, the risk of jackknifing will be reduced and the driver should still be able to maintain steering control. If only the trailer is equipped with ABS, it is less likely that the trailer will swing out to one side.

Vehicles with Anti-Lock Braking Systems (ABS) have yellow malfunction lamps.

When performing a static leakage test on a double combination vehicle with air brakes, the leakage rate should be no more than 3 psi in one minute. If air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

In a vehicle with air brakes, the brake lights are activated when the brake pedal is pushed and air pressure moves an electric switch. With the application of air pressure, the switch will then turn on the brake lights.

In an air brake system, the air compressor governor controls when the air compressor pumps air into the air storage tanks.

If you use the parking brakes when the weather is very wet and the temperature is below freezing, the brakes may become frozen, preventing the vehicle from moving.

Never apply the brake pedal if your spring breaks are activated. Brakes can be damaged if they are subject to both springs and air pressure.

The air that enters air storage tanks in an air brake system usually contains a certain amount of water and compressor oil. Because accumulations of these materials can damage the braking system, tanks are equipped with drains to allow their removal.

Water and compressor oil are removed from air storage tanks through a drain valve. The water and oil can damage the brakes if left to accumulate in the system. Manually operated tanks must be drained every day to remove this build-up.

While driving, spring brakes are generally held in place by air pressure. If the air pressure gets low enough, the springs will activate the brakes.

The stab braking method for emergency stops involves fully applying the brakes until they lock up. The brakes are then released until the wheels start rolling, then the process is repeated.

Before driving a vehicle with a dual air system, allow time for the air compressor to build up a minimum pressure of 100 psi in both the primary and secondary systems.

A one-way check valve is required to be between an air compressor and the first main reservoir. This valve prevents air from escaping the system if the air compressor develops a leak.

To prevent the build up of oil and water in a vehicle's air tanks, manually operated air tank drains should be used at the end of each day of driving.

Truck tractors with air brakes built on or after March 1, 1997 must be equipped with Anti-Lock Braking Systems (ABS).

Truck tractors with air brakes that were manufactured on or after March 1, 1997 are required to be equipped with Anti-Lock Braking Systems (ABS). ABS is required in any other type of vehicle with air brakes that was manufactured on or after March 1, 1998.

Check each slack adjuster after parking on level ground, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure they do not move more than about one inch from where the push rod is attached. If they move more than one inch, they may be out of adjustment and will need to be fixed.

In an air brake system, the air compressor pumps air into the air storage tanks. The air compressor is controlled by the air compressor governor.

Air storage tanks are used to hold compressed air. The number and size of air tanks in an air brake system varies among vehicles.

The controlled braking method for emergency stops involves applying the brakes as hard as you can without locking the wheels. Keep steering wheel movements small when braking in this way.

It is essential that your low pressure warning light function properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.

Before starting down a hill, be sure to switch into a low gear. Gravity will increase your vehicle's speed as you travel downhill.