Your score review found missed questions about spring brakes, parking brakes, emergency brakes, or how air pressure changes brake behavior.
Study the weak area
What to understand before you answer.
Spring and parking brake questions test cause and effect. When air pressure changes, the brake system does not behave like a normal hydraulic car brake system.
01
Know the difference between service brakes and spring or parking brakes.
02
Understand why spring brakes can apply when air pressure drops too low.
03
Do not use the parking brake as a normal way to slow a moving vehicle.
04
Connect pressure behavior to the safe driver response.
Before the questions
How to improve this score.
Review the air brakes study page.
Answer each question by asking which brake system is being described.
Review missed explanations for pressure behavior.
Repeat this drill before going back to mixed air brakes practice.
Common traps to watch for
Assuming parking brakes work independently of air pressure behavior.
When this pattern appears in a missed answer, review the explanation before trying another set.
Thinking air pressure applies spring brakes instead of holding them back.
When this pattern appears in a missed answer, review the explanation before trying another set.
Thinking the parking brake is for routine slowing.
When this pattern appears in a missed answer, review the explanation before trying another set.
Using parking or spring brakes as ordinary slowing tools.
When this pattern appears in a missed answer, review the explanation before trying another set.
Treating parking brake failure as less important than service brake failure.
When this pattern appears in a missed answer, review the explanation before trying another set.
Practice questions
CDL Spring and Parking Brakes Drill Quiz
Answered 0 / 20
Question 1
What are spring brakes?
Spring brakes are held back by air pressure. If air pressure is lost, the springs expand and apply the brakes automatically. They serve as both the emergency and parking brakes.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 2
If the spring brakes apply while you are driving, what should you do?
If air pressure falls below 20-45 psi, the spring brakes will engage automatically and bring the vehicle to a rapid stop. You must steer safely off the road before you lose complete mobility.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 3
What color is the tractor parking brake control valve in the cab?
The tractor parking brake control is a diamond-shaped, yellow, push-pull control knob.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 4
When should you NOT use the parking brake?
Do not use the parking brake if the brakes are extremely hot (they could warp) or if they are very wet in freezing temperatures (they could freeze locked). Use wheel chocks instead.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 5
How do you manually check the slack adjusters on S-cam brakes?
To check slack adjusters, you must release the parking brakes so there is no tension on the system. If a slack adjuster moves more than about one inch when pulled by hand, it probably needs adjustment.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 6
What is the purpose of the modulating control valve?
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.
Question 7
What provides the braking power for spring brakes?
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.
Question 8
If your vehicle has dual parking control valves, what can you use the separate air tank for?
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.
Question 9
How do you check that the spring brakes come on automatically?
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.
Question 10
When is it safe to leave your vehicle unattended without applying the parking brakes or chocking the wheels?
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.
Question 11
What do spring brakes normally do when air pressure drops too low?
Spring brakes are held back by air pressure. If pressure drops too low, the springs can apply the brakes.
Source focusCDL Manual - Air Brakes: spring brakes
Study focusUnderstand spring brake behavior when pressure drops.
Common trapThinking air pressure applies spring brakes instead of holding them back.
Question 12
What is the safest reason to test the parking brake before driving?
The parking brake must hold the vehicle when parked. It is not a normal service brake for highway stopping.
Source focusCDL Manual - Air Brakes: parking brake check
Study focusUnderstand why the parking brake is tested.
Common trapThinking the parking brake is for routine slowing.
Question 13
Why should you not use spring brakes for normal slowing?
Spring brakes are designed for parking and emergency application. Normal slowing should be done with the service brakes.
Source focusCDL Manual - Air Brakes: spring brakes
Study focusUse spring brakes for their intended parking and emergency role.
Common trapUsing parking or spring brakes as ordinary slowing tools.
Question 14
What should you do if the parking brake will not hold during a pre-trip test?
A parking brake that will not hold is a serious defect. It should be corrected before the vehicle is operated.
Source focusCDL Manual - Air Brakes: parking brake test
Study focusRespond safely to a failed parking brake test.
Common trapTreating parking brake failure as less important than service brake failure.
Question 15
Why should you not leave an air brake vehicle unattended without securing it correctly?
A parked commercial vehicle must be secured. Parking brakes and wheel chocks are used according to situation and rules to prevent movement.
Source focusCDL Manual - Air Brakes: parking
Study focusSecure an unattended air brake vehicle.
Common trapAssuming service brakes hold a parked vehicle after the driver leaves.
Question 16
If you cross the air lines when hooking up to an older trailer, what will happen?
If lines are crossed, air goes to the service brakes instead of releasing the spring brakes. You won't be able to move (if spring brakes are working) or you won't have service brakes (if spring brakes are broken/missing on older trailers).
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 17
When supplying air to a trailer, at what pressure should the trailer emergency brakes release?
The trailer spring brakes (emergency brakes) release when you push in the red trailer air supply valve and air pressure builds up in the trailer's emergency system.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 18
When inspecting the trailer before coupling, you should make sure the trailer wheels are:
Before backing under a trailer, ensure the trailer wheels are chocked (blocked) or the spring brakes are properly applied so the trailer doesn't roll away when you push against it with the fifth wheel.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 19
When uncoupling, why do you apply the parking brakes, lower the landing gear, and disconnect the air lines BEFORE pulling the fifth wheel release handle?
You secure the trailer (brakes and landing gear) and disconnect lines first so that when you finally release the kingpin and pull away, the trailer is fully supported and won't rip the air lines out.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.
Question 20
What is the purpose of the trailer air supply control valve (the red octagonal knob)?
The red trailer air supply valve is pushed in to supply air to the trailer (releasing the trailer emergency brakes) and pulled out to shut off the air and apply the trailer emergency brakes.
Study focusUnderstand how spring brakes and parking brakes behave when air pressure changes.
Common trapAssuming parking brakes work independently of air pressure behavior.