Wisconsin CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

When the low air pressure warning first activates, what is the correct action?

Accepted Answer

Get the vehicle safely stopped immediately, while the service brakes still respond — Do not wait for the spring brakes to set on their own; stop safely at once, while you still have control of the service brakes.

Answer

Keep driving until the spring brakes set themselves

Answer

Pump the pedal to rebuild pressure fast

Answer

Release the parking brake control to reset the system

Question 2

Which sequence describes the stab braking method?

Accepted Answer

Apply fully, release when the wheels lock, then reapply fully once they roll again — Stab braking means fully applying the brakes, letting off when the wheels lock, and reapplying fully once they start rolling again.

Answer

Press lightly and hold steady until the vehicle stops

Answer

Pump the pedal quickly the whole way down the road

Answer

Apply partway, then ease off little by little

Question 3

Your dual air system takes far too long to build pressure during the pre-trip check. What is the danger if you drive it anyway?

Accepted Answer

Tank pressure can fall too low while you are driving and force an emergency stop — A system that recharges too slowly may not keep up with the air you use, so tank pressure can sink dangerously low out on the road; the manual says to have it repaired before the vehicle moves.

Answer

The governor will begin cutting in far below its normal setting

Answer

The alcohol evaporator will flood the tanks with fluid

Answer

The ABS lamp will stay lit until the tanks are drained

Question 4

Someone pulls out ahead of you and you have room to stop. Besides slowing the vehicle, what should your hard braking accomplish?

Accepted Answer

It should keep the vehicle tracking straight and leave you able to turn if you must — The manual asks you to brake so the vehicle holds its line and steering stays available, which is exactly why controlled braking and stab braking are taught instead of simply locking the wheels.

Answer

It should lock every wheel quickly so the tires scrub off speed

Answer

It should throw the braking load onto the trailer alone

Answer

It should let the spring brakes finish the stop for you

Question 5

Only the tractor of your combination has ABS, and the trailer starts to swing out while you are braking hard. What should you do?

Accepted Answer

Ease up on the pedal when it is safe to, until the trailer falls back into line — ABS on the tractor alone cannot keep the trailer in line, so watch it and ease off the pedal whenever you can safely do that until the rig tracks straight again.

Answer

Push the pedal down harder so the trailer brakes drag it back

Answer

Apply the trailer hand valve fully and steer toward the shoulder

Answer

Pull the parking brake knob out to straighten the rig

Question 6

You brake hard on a slick road in a truck built without ABS. What is the result if the wheels on the steering axle lock up?

Accepted Answer

You can no longer steer the vehicle — Front wheels that have stopped turning will not answer the steering wheel, so the truck keeps going wherever its momentum takes it until those wheels roll again.

Answer

The trailer brakes release by themselves

Answer

The spring brakes apply automatically

Answer

The air compressor stops pumping

Question 7

In stab braking, why must you wait for the wheels to start rolling before reapplying the brakes?

Accepted Answer

Reapplying before the wheels roll keeps the vehicle from straightening out — It can take up to a second for the wheels to roll again, and reapplying too soon keeps the vehicle from straightening out.

Answer

So the tanks have time to refill

Answer

So the ABS can reset itself

Answer

So the drums have time to cool

Question 8

When may you fully apply the brakes during an emergency stop?

Accepted Answer

When you always drive a vehicle with working ABS on all axles — The single exception applies only if every vehicle you drive is a straight truck or combination whose ABS works on all axles; in that case an emergency stop may use the brakes fully.

Answer

Whenever the road is wet

Answer

Only when the trailer is empty

Answer

Only at speeds below 20 mph

Question 9

Why is it risky to let the spring brakes set themselves instead of stopping under control first?

Accepted Answer

A light load or slick road can skid, and a heavy load stops slowly since the springs miss some axles — A light load or a slick road can skid out of control when the springs grab, and a heavy load stops slowly because the spring brakes do not act on every axle.

Answer

The spring brakes only work above 60 psi

Answer

They apply the front brakes twice as hard

Answer

They always overheat the drums instantly

Question 10

During the inspection you find that the low air pressure warning signal never comes on. Why does the manual treat that as a serious hazard?

Accepted Answer

Air could drain away unnoticed, so a single-circuit vehicle may brake suddenly and a dual system will take much longer to stop — Without the warning you would never know pressure was bleeding away; a single-circuit vehicle can brake abruptly on its own, and a dual system simply needs more room to stop, with little braking left before the springs set.

Answer

The parking brakes could release on their own while you drive

Answer

The compressor would keep running and overheat

Answer

The ABS would shut itself down above highway speed

Question 11

How do you use the controlled braking method in an emergency?

Accepted Answer

Brake as hard as possible short of locking the wheels, with only small steering movements — Press the brakes about as firmly as possible while stopping just short of a wheel lockup, keeping steering inputs tiny; release and reapply if a wheel locks or you need to steer more.

Answer

Lock every wheel and steer hard toward the shoulder

Answer

Pump the pedal in a steady rhythm

Answer

Apply only the trailer brakes with the hand valve

Question 12

If you keep driving after the low air warning comes on, what limits your braking?

Accepted Answer

Controlled braking works only while air remains, and the spring brakes set at 20 to 45 psi — You can only brake in a controlled way while air remains in the tanks, and the spring brakes will set once pressure drops to the 20-to-45 psi range.

Answer

The parking brake locks the steering wheel

Answer

The compressor overheats and quits

Answer

The stop lamps stop working first

Wisconsin CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. When the low air pressure warning first activates, what is the correct action?

2. Which sequence describes the stab braking method?

3. Your dual air system takes far too long to build pressure during the pre-trip check. What is the danger if you drive it anyway?

4. Someone pulls out ahead of you and you have room to stop. Besides slowing the vehicle, what should your hard braking accomplish?

5. Only the tractor of your combination has ABS, and the trailer starts to swing out while you are braking hard. What should you do?

6. You brake hard on a slick road in a truck built without ABS. What is the result if the wheels on the steering axle lock up?

7. In stab braking, why must you wait for the wheels to start rolling before reapplying the brakes?

8. When may you fully apply the brakes during an emergency stop?

9. Why is it risky to let the spring brakes set themselves instead of stopping under control first?

10. During the inspection you find that the low air pressure warning signal never comes on. Why does the manual treat that as a serious hazard?

11. How do you use the controlled braking method in an emergency?

12. If you keep driving after the low air warning comes on, what limits your braking?

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