Use this set after Test 1 when air brake warnings, leakage checks, or pressure behavior still need review.
This set gives a fresh air brakes score check with more emphasis on applying system knowledge to safe driver actions.
Separate part-function questions from warning, leakage, and spring-brake behavior.
Notice whether the question describes a single vehicle or a combination vehicle.
Choose the action that keeps the vehicle safe before it moves or continues.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
When this pattern appears in a missed answer, review the explanation before trying another set.
If air pressure does not build up fast enough, the pressure may drop too low during driving, requiring an emergency stop. Don't drive until it is fixed.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
A dual air brake system has two separate air brake systems (primary and secondary), each with its own air tanks and lines, but both are operated by the same brake pedal.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
If one air system fails, the other will still work. However, the brakes will not work as well, and it will take longer to stop. You should stop safely and park the vehicle until fixed.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
Air tanks should be drained at the end of each day of driving. Moisture and oil collect in the tanks from the air compressor, and if not drained, they can freeze in cold weather and cause brake failure.
Study focusUnderstand compressor, governor, reservoir, and air supply behavior.
Common trapConfusing compressor cut-in/cut-out behavior with brake application.
For a single vehicle (like a straight truck or bus), the static air leakage rate must be less than 2 psi in one minute.
Study focusApply the correct static and applied air leakage test limits.
Common trapMixing up single-vehicle and combination-vehicle leakage limits.
Some vehicles have a control handle on the dashboard that allows you to apply the spring brakes gradually. This modulating valve gives you more control when using spring brakes for an emergency stop.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
You must downshift before starting down a grade. If you try to downshift after your speed has built up, you will not be able to shift into a lower gear and may lose engine braking entirely.
Study focusUse inspection habits to catch unsafe defects before driving.
Common trapChecking only obvious items and missing brake, tire, coupling, or defect-report steps.
In an emergency, you want to stop as quickly as possible without locking the wheels (controlled braking) or locking and releasing (stab braking) so you maintain steering control.
Study focusUse pre-trip inspection habits to identify unsafe vehicle-system defects before driving.
Common trapMemorizing a walk-around order without understanding which defects make the vehicle unsafe.
Stab braking is an emergency braking technique used on vehicles without ABS. You lock the wheels, release the brakes when they lock, and reapply as soon as they start rolling again.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Brakes are designed to work best when the vehicle has a moderate load. A very heavy load increases stopping distance due to momentum, but an empty vehicle also takes longer to stop because it lacks traction and the tires can lock up easily.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
Air brakes have an added delay. Total stopping distance is Perception Distance + Reaction Distance + Brake Lag Distance + effective Braking Distance.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
Brake lag is about half a second. At 55 mph, a vehicle travels about 32 feet in that half-second before the brakes actually begin to engage.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
The S-cam drum brake is the most common type of foundation brake found on commercial vehicles.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
When you apply the brakes, air pressure pushes the pushrod, turning the S-cam, which forces the brake shoes away from one another and presses them against the inside of the brake drum.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
Spring brakes rely on the mechanical force of powerful springs. Air pressure is actually used to hold the springs back; when air pressure is released, the springs expand and apply the brakes.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Some vehicles have a separate air tank with its own control valve to release the spring brakes temporarily. This provides enough air to move the vehicle to a safe location if the primary air is lost.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
To test the automatic application of the spring brakes, fan off the air pressure by pumping the brake pedal. The parking brake valve should pop out automatically between 20 and 45 psi.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
The supply pressure gauge (or gauges, in a dual system) tells you how much air pressure is available in the storage tanks.
Study focusUnderstand compressor, governor, reservoir, and air supply behavior.
Common trapConfusing compressor cut-in/cut-out behavior with brake application.
The application pressure gauge shows how much air pressure you are applying to the foundation brakes when you press the brake pedal.
Study focusIdentify key air brake parts and explain how the system produces braking force.
Common trapMemorizing part names without understanding what each part does.
Never leave your vehicle unattended without applying the parking brakes or chocking the wheels. A heavy vehicle can easily roll and cause catastrophic damage.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.