Idaho CDL — General Knowledge: Safe Driving Practices Practice Test

Question 1

Baffles in a liquid tank help control forward-and-backward surge. Which surge can still happen, and why does it matter?

Accepted Answer

Side-to-side surge, which can cause a rollover — Baffles have holes that let liquid flow through, taming front-to-back movement. The liquid can still move from side to side, and that movement is capable of rolling the vehicle over.

Answer

Upward surge, which can lift the tank off its frame

Answer

Diagonal surge, which unlocks the valves

Answer

No surge at all remains

Question 2

How does steering differ when you back with a trailer instead of backing a straight truck?

Accepted Answer

You turn the wheel opposite to the way you want the trailer to go, then turn the other way to follow it — In a vehicle with no trailer you turn the top of the wheel toward where you want to go. With a trailer you first steer the opposite way, and after the trailer begins turning you reverse the wheel so the tractor follows it.

Answer

You keep the wheel locked straight

Answer

You turn the wheel the same way as in a car, only faster

Answer

You steer only with the trailer hand valve

Question 3

When you uncouple and disconnect the trailer's electrical cable, how should the cable be hung?

Accepted Answer

With the plug pointing down, so moisture can't get in — The uncoupling steps say to hang the cable so its plug faces downward, which keeps moisture from getting into it.

Answer

Coiled on the catwalk floor

Answer

With the plug pointing up

Answer

Draped over the fifth wheel

Question 4

You post a lookout before backing a school bus. What is the lookout's job?

Accepted Answer

To warn you about obstacles, approaching people and other vehicles, not to direct the backing — The lookout is there to give warnings about obstacles, people coming near and other vehicles. The manual says the lookout should not be telling the driver how to back the bus.

Answer

To give you step-by-step steering directions

Answer

To ride in the rear seat

Answer

To hold traffic with a stop sign

Question 5

The manual's chart gives triples a rearward amplification of 3.5. What does that figure mean?

Accepted Answer

The rear trailer of a set of triples rolls over 3.5 times more easily than a five-axle tractor — Rearward amplification is what produces the crack-the-whip effect. A value of 3.5 means the rearmost trailer of a set of triples can be tipped 3.5 times more easily than a five-axle tractor.

Answer

The rear trailer carries 3.5 times the weight

Answer

Triples need 3.5 times the stopping distance

Answer

Triples are 3.5 times as long as a tractor

Question 6

What does the combination vehicles section blame for the majority of truck drivers killed in crashes?

Accepted Answer

Truck rollovers — The section says over half of the truck drivers who die in crashes die in rollovers, which is why it stresses keeping cargo low and taking turns slowly.

Answer

Rear-end collisions

Answer

Brake failures

Answer

Jackknifes

Question 7

Bulkheads split a liquid tank into several smaller compartments. What should the driver watch when loading and unloading them?

Accepted Answer

Weight distribution, so the front or rear isn't overloaded — With a compartmented tank the driver has to mind how the weight is spread, taking care not to load the front or the rear of the vehicle too heavily.

Answer

Filling the rear compartment first every time

Answer

The color of each compartment

Answer

Keeping every compartment exactly half full

Question 8

When inspecting any tank vehicle, which problem matters most to look for?

Accepted Answer

Leaks — The manual singles out leaks as the top item on every tank vehicle. Hauling a liquid or gas load in a tank that leaks is a crime, and the driver can be cited, stopped from going on, and held liable for cleanup.

Answer

Worn seat covers

Answer

Loose mud flaps

Answer

Faded paint

Question 9

When you inspect a coupled fifth wheel, where should the locking jaws be?

Accepted Answer

Around the shank of the kingpin, not the head — The walk-around check calls for the jaws to be closed on the kingpin's shank. Jaws sitting on the kingpin's head mean the coupling is not secure.

Answer

Around the head of the kingpin

Answer

Open, with the kingpin resting on top

Answer

Clamped on the trailer apron

Question 10

Some tractors have 'dead end' or dummy couplers. What are they for?

Accepted Answer

Holding unused air hoses so water and dirt stay out of the couplers and lines — Air hoses that aren't connected to a trailer can be attached to dummy couplers, which keeps the air supply clean by blocking water and dirt.

Answer

Storing spare glad hand seals

Answer

Testing the trailer brakes

Answer

Bleeding moisture from the air tanks

Question 11

While you are backing, the trailer begins to drift off the intended path. How does the manual say to correct it?

Accepted Answer

Steer toward the drift right away, moving the top of the wheel in that direction — Drift should be fixed the moment you notice it, by moving the top of the wheel the same way the trailer is drifting. Pull-ups can be used to reposition when needed.

Answer

Apply the trailer hand valve

Answer

Wait until the trailer is well off course, then pull forward

Answer

Speed up so the trailer straightens

Question 12

During coupling, after you supply air to the trailer, how does the manual have you check for crossed air lines?

Accepted Answer

Shut the engine off, apply and release the trailer brakes, and listen for them working — With the engine off you can hear the trailer brakes. Working them on and off should produce the sound of the brakes moving and of air escaping on release; if not, the lines may be crossed.

Answer

Drive forward and see whether the trailer follows

Answer

Feel each hose for heat

Answer

Look for the gauge needles to cross

Idaho CDL — General Knowledge: Safe Driving Practices practice test

Study questions with answers

1. Baffles in a liquid tank help control forward-and-backward surge. Which surge can still happen, and why does it matter?

2. How does steering differ when you back with a trailer instead of backing a straight truck?

3. When you uncouple and disconnect the trailer's electrical cable, how should the cable be hung?

4. You post a lookout before backing a school bus. What is the lookout's job?

5. The manual's chart gives triples a rearward amplification of 3.5. What does that figure mean?

6. What does the combination vehicles section blame for the majority of truck drivers killed in crashes?

7. Bulkheads split a liquid tank into several smaller compartments. What should the driver watch when loading and unloading them?

8. When inspecting any tank vehicle, which problem matters most to look for?

9. When you inspect a coupled fifth wheel, where should the locking jaws be?

10. Some tractors have 'dead end' or dummy couplers. What are they for?

11. While you are backing, the trailer begins to drift off the intended path. How does the manual say to correct it?

12. During coupling, after you supply air to the trailer, how does the manual have you check for crossed air lines?

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