Idaho ITD CDL General Knowledge Practice Test 3
Test 3 of 5. Pick an answer for each question to see if it is right and why; your score appears at the end. You need 40 correct answers to pass, the same ratio as the real Idaho test.
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
-
1. Why does extra weight make a long downgrade more dangerous even when the brakes are in good order?
Show answer
Answer B: Gravity adds to the momentum and the brakes heat up faster
The heavier the vehicle, the more energy the brakes must turn into heat, and heat is exactly what makes brakes fade on a long descent.
-
2. A fire has started in the vehicle. How should the extinguisher be used?
Show answer
Answer B: Stay as far back as the reach of the extinguisher allows, stand upwind, and aim at the base of the fire
Aiming at the base attacks what is actually burning, and staying upwind and well back protects the driver from heat, smoke and the flames themselves.
-
3. What is the minimum tread depth required in every major groove of a steering axle tire?
Show answer
Answer D: 4/32 inch
Federal rules set a higher tread minimum for front steering tires than for other positions because a steering tire failure is far harder to control.
-
4. Federal rules say a commercial vehicle may not be driven unless what is true of its cargo?
Show answer
Answer B: It is properly distributed and adequately secured
The basic federal requirement is that the load be distributed properly and secured well enough that it cannot move, whatever the paperwork says.
-
5. Below 40 mph, what following distance does the standard commercial rule of thumb call for?
Show answer
Answer C: One second for every 10 feet of vehicle length
The base rule allows one second of space for each 10 feet of vehicle length while speed stays under 40 mph.
-
6. Under the federal air brake standard, the low air pressure warning must come on before reservoir pressure drops below what level?
Show answer
Answer A: Before pressure falls below 60 psi
Federal Motor Vehicle Safety Standard 121 requires the warning to operate while service reservoir pressure is still above 60 psi, which leaves enough air to bring the vehicle to a normal stop.
-
7. How many questions does the Idaho CDL General Knowledge test contain, and how many must be answered correctly?
Show answer
Answer A: 50 questions, with 40 correct required
The Idaho CDL manual lists the General Knowledge test as 50 questions with a minimum of 40 correct answers to pass.
-
8. Why does a load need to be balanced from side to side?
Show answer
Answer B: Because a heavy side raises the rollover risk and can overload the tires and springs on that side
An uneven load tips the balance of the vehicle in curves and pushes the tires and suspension on the loaded side past their rating.
-
9. You have just passed another vehicle on a two lane road. What tells you it is safe to return to your lane?
Show answer
Answer B: You can see the whole front of that vehicle in your right mirror
Seeing the entire front of the vehicle you passed in your mirror proves you are far enough ahead to move back over without cutting the driver off.
-
10. Which lamp must make the rear registration plate legible after dark?
Show answer
Answer C: A white lamp that lights the plate
A white license plate lamp is required so the plate can be read at night, and a burned out one is a defect like any other lamp.
-
11. In the seven-step method, what comes immediately after starting the engine and inspecting inside the cab?
Show answer
Answer D: Turn off the engine and check the lights
Step four shuts the engine down and switches on the lamps needed for driving so the driver can leave the cab and confirm they actually work.
-
12. You are taking a tightly curved highway exit ramp in a long combination. Where should the tractor be placed within the lane?
Show answer
Answer D: Toward the outside of the curve, leaving room for the trailer to track inside
Because the trailer wheels cut to the inside of the curve, the tractor has to be kept out toward the outer edge so the trailer does not drop a wheel off the inside edge.
-
13. What is the purpose of an escape ramp on a mountain grade?
Show answer
Answer C: To stop a runaway vehicle without injuring the driver
Escape ramps use soft material or a steep upgrade to bring a vehicle with failed brakes to a controlled stop.
-
14. You are not certain that your loaded vehicle will clear a low overpass. What should you do?
Show answer
Answer A: Take another route rather than risk it
There is no safe way to guess at a clearance, and striking a bridge endangers everyone on and under it, so the only correct choice is a different route.
-
15. Why is braking while in a curve dangerous in a heavy vehicle?
Show answer
Answer A: The wheels lock more easily and the vehicle can skid
Tires already using their grip to turn have little left for braking, so hard braking in a curve locks the wheels; slow down before the curve instead.
-
16. Which restriction does ITD place on every Idaho CDL holder aged 18, 19 or 20?
Show answer
Answer A: The K restriction, limiting the driver to intrastate operation
ITD places the K restriction, meaning intrastate operation only, on the record of every CDL holder who is 18, 19 or 20 years old.
-
17. Why are the windshield wipers on the pre-trip list even before a trip in fine weather?
Show answer
Answer C: Because weather can change and a wiper failure leaves the driver without a clear view
Rain, spray or mud can arrive at any point in a long trip, and a wiper that fails then leaves the driver with no way to clear the windshield.
-
18. What does gross vehicle weight mean, as opposed to gross vehicle weight rating?
Show answer
Answer B: The actual weight of the single vehicle plus everything it is carrying
Gross vehicle weight is what the vehicle actually weighs at that moment; the rating is the maximum the manufacturer allows it to weigh.
-
19. On a set of dual tires, which condition must be reported as a defect?
Show answer
Answer D: The two tires are touching each other or rubbing on part of the vehicle
Duals that touch each other or the vehicle overheat and wear quickly, so they must be separated by proper spacing and inflation before driving.
-
20. What is the best practice when fog is thick enough to hide the road ahead?
Show answer
Answer B: Slow down before entering the fog, and if visibility is too poor, pull off into a rest area or truck stop until it improves
The safest choice in heavy fog is not to be driving in it, and if you are already in it your speed has to come down before your visibility does.
-
21. What is the correct way to make a right turn in a long vehicle?
Show answer
Answer D: Keep the rear of the vehicle close to the curb and swing wide only as you complete the turn
Swinging left before a right turn invites another driver to move into the gap on your right, so any extra width is taken as the turn is finished.
-
22. What can repeated violations of the federal phone and texting rules cost a commercial driver?
Show answer
Answer D: Disqualification of the commercial driver license
Multiple convictions for using a hand-held phone or texting while driving a commercial vehicle lead to disqualification, on top of fines for driver and carrier.
-
23. How do you confirm that the coupling is locked before pulling out of the yard?
Show answer
Answer D: By locking the trailer brakes and pulling gently forward against them
The tug test loads the coupling in the direction that would pull it apart, so if the jaws are not closed on the kingpin you find out at walking pace.
-
24. Cargo falls from your trailer and causes a crash behind you. Who is likely to answer for it?
Show answer
Answer C: The driver and the carrier, since securing the load on the road is their duty
Whoever loaded the vehicle, the driver and the carrier are responsible for the load being secure while it is on the road.
-
25. Why should a driver avoid traveling alongside another vehicle for any length of time?
Show answer
Answer D: You lose your escape route and you may be sitting in the other driver blind spot
Running beside someone leaves nowhere to move if you have to change lanes, and the other driver may not know you are there at all.
-
26. A car is following you far too closely. What is the safest response?
Show answer
Answer A: Open up more space ahead so you can slow gradually, avoid sudden changes, and do not speed up
Extra room in front lets you slow smoothly instead of braking hard, which is exactly what the driver behind cannot cope with.
-
27. A chain rated at 6,600 pounds is fitted with a hook rated at 4,700 pounds. What is the working load limit of that assembly?
Show answer
Answer A: 4,700 pounds, the rating of the weakest part
An assembly is only as strong as its weakest component, so hooks, binders and links all count and the lowest rating governs.
-
28. Why does the commercial driver manual tell you to look far down the road instead of only at the vehicle ahead?
Show answer
Answer D: So you can adjust smoothly instead of braking hard at the last moment
A heavy vehicle cannot react quickly, so early information lets you slow gradually rather than make a sudden stop or swerve.
-
29. Why is driving much slower than the rest of the traffic dangerous?
Show answer
Answer B: Other drivers must keep passing you, which creates conflicts
Traffic that has to work its way around you produces lane changes and closing speeds, which is why a large speed difference is itself a hazard.
-
30. When is tire pressure most accurately compared with the recommended figure?
Show answer
Answer B: When the tires are cold, before the vehicle has been driven
Recommended pressures are cold pressures, so a reading taken before the tires have heated up is the only one that can be compared directly.
-
31. You find a defect during the pre-trip inspection. What must happen before the vehicle is driven?
Show answer
Answer C: It must be repaired, or the vehicle must not be driven
Writing a defect down does not make the vehicle safe; a defect that affects safe operation has to be corrected before the trip starts.
-
32. A tire has a cut deep enough to expose the body ply or the belt material. What does that mean?
Show answer
Answer D: The vehicle must not be driven on that tire
Once the structural plies are exposed the casing has lost its strength, and federal rules treat that tire as unfit for the road.
-
33. You are loading a flatbed that has no sides or bulkheads. How must the cargo be held?
Show answer
Answer D: By tiedowns, blocking or bracing, since there are no walls to keep it from shifting or falling off
Open decks depend entirely on securement devices; every article must be tied down or otherwise immobilized so it cannot move, spill or fall.
-
34. What should you check about the fuel tank during the walkaround?
Show answer
Answer A: That it is securely mounted, the cap is on tight and there are no leaks
A loose tank or a missing cap can spill fuel, and any fuel leak is a fire hazard that makes the vehicle unsafe to drive.
-
35. How does bracing differ from blocking when securing cargo?
Show answer
Answer B: Bracing runs from the upper part of the cargo to the floor or walls to keep it from moving, while blocking fits snugly against the cargo
Blocking is shaped to fit against the front, back or sides of a piece of cargo; bracing supports it from above so it cannot tip or shift.
-
36. Why can an empty truck need a longer stopping distance than a loaded one?
Show answer
Answer C: An empty vehicle has less traction, so its wheels lock up more easily
Brakes and tires are designed for a loaded vehicle, and with little weight on the axles the tires grip less and lock sooner.
-
37. What is the minimum tread depth for tires in positions other than the steering axle?
Show answer
Answer A: 2/32 inch
Drive and trailer tires must keep at least 2/32 inch of tread in a major groove, measured away from tie bars and fillets.
-
38. After coupling, where should the fifth wheel release handle be?
Show answer
Answer A: In the locked position with the safety latch in place
The handle must be pushed in and latched, because a handle left out means the jaws can open and release the trailer while you are driving.
-
39. Why do worn tires lose grip so quickly on a wet road?
Show answer
Answer D: Shallow tread cannot move water out from under the tire
The grooves in a tire exist to channel water away so the rubber can touch the road, and a worn tire has lost that capacity.
-
40. Using the snub braking method on a downgrade, when does the driver release the brakes?
Show answer
Answer A: After speed has dropped about 5 mph below the safe speed
The driver brakes firmly to about 5 mph under the chosen safe speed, releases to let the brakes cool, then repeats when the safe speed returns.
-
41. Taking your eyes off the road for about five seconds at highway speed means traveling roughly how far unseen?
Show answer
Answer A: About the length of a football field
At highway speed a five second glance away covers roughly 100 yards, which is far more road than any driver can afford to travel blind.
-
42. How far ahead can a driver see with low beams and with high beams?
Show answer
Answer C: About 250 feet with low beams and about 350 to 500 feet with high beams
Low beams reach roughly 250 feet and high beams roughly 350 to 500 feet, and speed at night has to stay inside the distance the lights really show.
-
43. When a helper guides you while backing, what should be agreed on before you start?
Show answer
Answer D: A set of hand signals, especially the signal that means stop
The driver and helper must agree on signals in advance, above all the stop signal, because they usually cannot hear each other.
-
44. What should you check about the air hoses and the electrical cord running to the trailer?
Show answer
Answer D: That they are free of damage, properly connected and not dragging or rubbing
Lines that chafe on the frame or drag on the road wear through, and a broken line takes away trailer braking or trailer lighting without warning.
-
45. On packed snow, how much should a commercial driver reduce speed?
Show answer
Answer D: By about one half or more
Packed snow costs far more traction than rain, so speed should be cut by half or more.
-
46. The rear wheels of your vehicle lock during braking and the rear starts to slide sideways. What should you do first?
Show answer
Answer A: Stop braking so the rear wheels can roll again, then steer quickly in the direction you want to go
Locked wheels have no side grip; releasing the brakes restores traction and then countersteering brings the vehicle back into line.
-
47. An oncoming vehicle at night has bright headlights that are making it hard to see. What should you do?
Show answer
Answer B: Look toward the right edge of your lane and avoid looking directly at the lights
Looking at the right edge of the road keeps your eyes off the glare while you stay in your lane; glare can leave you nearly blind for several seconds.
-
48. Which shock absorber condition is a defect?
Show answer
Answer C: A shock that is leaking, broken or disconnected at either mounting
A shock that has lost its fluid or its mounting no longer damps the suspension, so the wheel bounces and loses contact with the road.
-
49. Who may remove an out-of-service sticker from a commercial vehicle?
Show answer
Answer B: Only an authorized person, and only after the defect that caused it has been repaired
The sticker stays on the vehicle until the repairs are made and an authorized person removes it, so nobody can simply peel it off and drive away.
-
50. Which vehicle condition makes hydroplaning more likely?
Show answer
Answer C: Tires that are worn or underinflated
Tread depth and correct pressure are what let a tire push water aside, so worn or soft tires lift onto the water film at lower speeds.