Missouri DOR CDL General Knowledge Practice Test 8
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
-
1. You are on a freeway and see brake lights come on in several vehicles far ahead of you. What should you do?
Show answer
Answer A: Ease off the accelerator and get ready to slow down
Brake lights well ahead are an early warning that traffic is slowing, and acting on them gives a heavy vehicle the room it needs.
-
2. How often must every commercial motor vehicle receive a periodic inspection?
Show answer
Answer C: At least once every twelve months
Federal rules require each commercial motor vehicle to pass a periodic inspection at least once in every twelve month period.
-
3. Besides allowing the move at all, what does an oversize load permit usually set out?
Show answer
Answer C: The route to be followed, the hours of travel allowed and the warning equipment needed
Permits for oversize movements normally name the roads that may be used, restrict the times of travel, and list the flags, signs and escorts required.
-
4. How long must the record of a periodic inspection be kept?
Show answer
Answer A: Fourteen months
The periodic inspection report is retained for fourteen months from the date of the report, which covers the full twelve month cycle plus a margin.
-
5. The brake pedal goes to the floor in a vehicle with hydraulic brakes. What can you do to build some braking pressure?
Show answer
Answer B: Pump the brake pedal rapidly, which may bring back enough pressure to slow the vehicle
Pumping can restore some hydraulic pressure; along with downshifting and the parking brake it is one of the ways to stop when the pedal fails.
-
6. What should be checked about the power steering system in the engine compartment?
Show answer
Answer D: That the fluid level is correct and the hoses and pump are not leaking
Losing power steering fluid means losing steering assistance, which can happen suddenly and makes a heavy vehicle very hard to turn.
-
7. On the Interstate System, what are the federal maximums for a tandem axle group and for gross vehicle weight?
Show answer
Answer B: 34,000 pounds and 80,000 pounds
The federal Interstate limits allow 34,000 pounds on a tandem axle group and 80,000 pounds gross.
-
8. An overpass you have driven under before now has a fresh layer of pavement on the road below it. Why does that matter?
Show answer
Answer B: The new layer raises the road and reduces the clearance
Repaving lifts the road surface, so the real clearance under a structure can be less than the height posted on it.
-
9. When speed doubles, what happens to braking distance?
Show answer
Answer D: It becomes roughly four times as long
Braking distance rises with the square of speed, so twice the speed needs about four times the distance to stop.
-
10. Part of looking well ahead is planning an out. What does that mean?
Show answer
Answer B: Keeping an escape path in mind in case traffic stops suddenly
Because a heavy vehicle often cannot stop in time, good drivers continuously note where they could steer if the space ahead closes.
-
11. How much sleep does a typical adult driver need each day to stay properly alert?
Show answer
Answer D: Seven to eight hours
Most adults need seven to eight hours of sleep in every 24 hours, and a driver who regularly gets less builds up a debt that shows up behind the wheel.
-
12. Why should both outside mirrors be checked over and over while backing?
Show answer
Answer B: Each mirror covers only part of the path and neither covers the blind spots, so people and objects can appear without warning
Working both mirrors in turn is the only way to follow the whole path of a vehicle you cannot see behind.
-
13. What score must be reached on each Missouri commercial driver license written examination?
Show answer
Answer C: 80 percent
Missouri requires 80 percent on every CDL knowledge examination, including the general knowledge test and each endorsement test.
-
14. Why must exhaust components be checked for contact with other parts of the vehicle?
Show answer
Answer B: Hot exhaust parts touching fuel lines, tires or wiring can start a fire
Exhaust pipes run hot enough to ignite fuel and melt insulation, so they must be kept clear of the fuel system, the tires and the electrical harness.
-
15. Which vehicle is most likely to be pushed around by a strong crosswind?
Show answer
Answer B: An empty van trailer
A large flat side with very little weight behind it gives the wind the most surface and the least resistance, which is the empty van trailer.
-
16. You are drifting in the lane, yawning constantly and cannot remember the last few miles. What is the only reliable cure?
Show answer
Answer C: Stopping in a safe place and sleeping
Those are classic drowsiness warning signs, and nothing except sleep repays the sleep the body is missing.
-
17. A vehicle becomes unsafe while you are already on the road. What does the federal rule allow?
Show answer
Answer A: Continuing only to the nearest place where repairs can safely be made
If stopping where you are would be more dangerous than moving, the rule allows you to reach the nearest place where the vehicle can safely be repaired, and no further.
-
18. Why does a cracked frame rail or cross member make a vehicle unsafe?
Show answer
Answer B: The frame carries the whole load, and a crack can spread until the structure fails
The frame is the backbone that supports the body, the load and the running gear, so a crack in it is a structural failure that grows with every mile.
-
19. Which wheel or rim condition must be treated as a defect during the walkaround?
Show answer
Answer C: Cracks, illegal welded repairs, or missing and loose lug nuts
Cracked or welded rims and missing or loose fasteners can let a wheel separate from the vehicle and must be corrected before driving.
-
20. A commercial driver is convicted of two serious traffic violations within three years. What is the result?
Show answer
Answer D: Disqualification for 60 days
Two serious traffic violations in a three year period bring a 60 day disqualification, and a third in the same period raises it to 120 days.
-
21. What is the driver looking for when the exhaust system is inspected?
Show answer
Answer B: Loose, broken or missing pipes, brackets or clamps, and signs that exhaust is leaking
A loose or leaking exhaust system can send carbon monoxide into the cab and can put hot gas against parts that will burn.
-
22. Rust streaks are running outward from the lug nuts on one wheel. What does this most likely indicate?
Show answer
Answer C: The lug nuts may be loose
Rust trails spreading from the nuts are a classic sign that the nuts have worked loose and the wheel has been moving on the studs.
-
23. For a modern truck with low-friction parts and a streamlined shape, which gear should be used going down a grade?
Show answer
Answer D: A gear lower than the one needed to climb the same grade
Newer trucks roll more freely than older ones, so the old rule of using the climbing gear no longer holds; a lower gear is needed for enough engine braking.
-
24. What blood alcohol concentration disqualifies the holder of a commercial driver license who is operating a commercial vehicle?
Show answer
Answer D: 0.04 or higher
Commercial drivers are held to 0.04, half the limit that applies to a driver of a passenger car in the same state.
-
25. At 55 mph, about how far does a vehicle travel during a typical 3/4 second perception time plus 3/4 second reaction time, before the brakes even begin to work?
Show answer
Answer C: About 120 feet
Each 3/4 second at 55 mph covers about 60 feet, so perception and reaction together use up roughly 120 feet before braking starts.
-
26. At a rest area you find that the load has shifted although the straps still feel tight. What should you do?
Show answer
Answer C: Correct the load before driving on, since a shifted load is no longer secure
Movement means the securement has already failed once, and a load that has shifted can shift again, so it is put right before the vehicle moves.
-
27. At the end of the day you find no defects on a property carrying vehicle. What does the federal rule require?
Show answer
Answer B: No written report is required, although the carrier may still ask for one
For property carrying vehicles the report is required only when a defect or deficiency is found or reported, although a carrier may impose a stricter policy.
-
28. A load overhangs the rear of the trailer. What must the driver check before leaving?
Show answer
Answer D: That the overhang is marked as required, with flags or lamps as conditions demand
A projecting load has to be made visible to other drivers, with flags in daylight and lamps when lights are required, so nobody runs into what they cannot see.
-
29. Your brakes have failed and you decide to use the parking brake to slow down. Why should you hold the release button or lever while doing so?
Show answer
Answer D: So you can release the brake at once if the wheels lock and the vehicle starts to skid
The parking brake can lock the wheels; keeping your hand on the release lets you let go the moment a skid starts and regain control.
-
30. Which winter preparation matters most for keeping the road in view?
Show answer
Answer D: Working wipers, washer fluid and a working defroster
Slush and road spray coat the windshield within minutes in winter, so wipers, washer fluid and the defroster are what keep any view at all.
-
31. Which description matches controlled braking during an emergency stop?
Show answer
Answer D: Apply the brakes as hard as you can without locking the wheels and keep steering movements small
Controlled braking keeps the wheels rolling just short of lockup, which gives the shortest stop while you keep the ability to steer.
-
32. A company mechanic serviced your truck this morning and signed the work order. Do you still have to inspect the vehicle?
Show answer
Answer B: Yes, the driver is still responsible for being satisfied the vehicle is safe
Shop work does not transfer the duty; the driver who takes the vehicle out remains responsible for being satisfied it is in safe operating condition.
-
33. You are dropping a loaded trailer in a yard. How far should the landing gear be lowered?
Show answer
Answer A: Until the pads make firm contact and the trailer weight is just off the fifth wheel
Cranking down until the gear is firmly on the ground and just lifting the load off the fifth wheel makes the trailer stable and lets the tractor pull out cleanly.
-
34. The engine has overheated and you need to check the coolant. What is the safe procedure with a pressurized radiator cap?
Show answer
Answer A: Shut the engine off, let the system cool, protect your hands, turn the cap slowly to its first stop so pressure escapes, step back, then remove it
A hot pressurized system throws steam and boiling coolant out of the opening, so the pressure is released slowly and only after the engine has cooled.
-
35. While checking the in-cab gauges after start-up, what should the coolant temperature gauge do?
Show answer
Answer C: Rise gradually to the normal operating range
A healthy cooling system warms the engine slowly; a gauge that shoots up or stays cold points to a problem with the thermostat, coolant or sensor.
-
36. What must be checked about the cargo doors and any tarpaulin before a trip?
Show answer
Answer B: That the doors are closed and latched and that any tarp is tied down securely
An unlatched door or a loose tarp can swing open or tear free at speed, spilling cargo or blocking the view of the traffic behind you.
-
37. How can a driver tell that a shipment includes hazardous materials?
Show answer
Answer B: The shipping paper describes them and the packages carry hazard warning labels
Hazardous materials are identified on the shipping paper with their shipping name and hazard class, and the packages themselves carry labels showing the hazard.
-
38. Your vehicle stalls on a railroad crossing and a train is coming. What should you do?
Show answer
Answer C: Get out at once and move toward the train, well off to one side
Leave the vehicle immediately and move at an angle toward the oncoming train, so that wreckage thrown forward by the impact travels away from you.
-
39. What should you do before backing into a space you have not used before?
Show answer
Answer A: Get out and walk around to check the path, the clearance and any obstacles
Walking the area first reveals low obstructions, soft ground and objects that never appear in the mirrors.
-
40. 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.
-
41. Why should water never be used on an electrical fire or a gasoline fire?
Show answer
Answer C: It spreads the fuel and conducts the current
Water carries current back to the person holding the hose and floats burning fuel outward, which is why a B:C rated extinguisher is carried instead.
-
42. An enforcement officer inspects your vehicle at the roadside and attaches an out-of-service sticker. What may you do?
Show answer
Answer C: Nothing until the defect is repaired; the vehicle may not be driven
An out-of-service order means the vehicle is unsafe, and no schedule, load or destination allows it to be driven before the defect is corrected.
-
43. In very hot weather, how often should you check the tires during a trip?
Show answer
Answer D: About every two hours or every 100 miles
Heat raises tire pressure and can lead to blowouts, so tires are checked about every two hours or 100 miles when it is very hot.
-
44. You need fuel and the canopy over the pumps is low. What is the safe way to handle the clearance?
Show answer
Answer B: Stop and check the height at the entrance and at the way out before committing
Clearance can differ at the entry, under the canopy and at the exit, and a sloping approach changes the effective height, so both ends have to be checked.
-
45. Why is a sudden, sharp lane change dangerous in a loaded heavy vehicle?
Show answer
Answer D: The vehicle can lean far enough to roll over, especially when the load sits high
A quick swerve throws the weight of a tall, heavy load sideways, and a rollover can begin before the tires ever slide.
-
46. During uncoupling, when may the fifth wheel locking lever be released?
Show answer
Answer D: Only after the landing gear is down and taking the weight of the trailer
The landing gear has to be supporting the trailer before the lock is released; otherwise the trailer nose can drop as soon as the tractor pulls out.
-
47. On a two lane road carrying traffic in both directions, where do the three warning devices go?
Show answer
Answer C: About 10 feet from the vehicle on the traffic side, 100 feet behind and 100 feet ahead
Traffic can approach from either direction, so one device goes close to the vehicle and one is placed about 100 feet away in each direction.
-
48. During the walkaround you notice a bulge in the sidewall of a trailer tire. What does it indicate?
Show answer
Answer B: Damage inside the tire, which can lead to a sudden failure
A bulge means the internal structure has broken and only the rubber is holding the air, so the tire can burst without warning.
-
49. 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.
-
50. 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.