Missouri DOR CDL General Knowledge Practice Test 4
Test 4 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 Missouri test.
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
-
1. What are the minimum ages for a Missouri commercial driver license used within the state and across state lines?
Show answer
Answer C: 18 within Missouri and 21 for interstate driving
Missouri issues a CDL at 18 for intrastate driving, but a driver must be 21 to operate a commercial vehicle in interstate commerce.
-
2. Why should the mirrors be checked repeatedly while you make a tight turn?
Show answer
Answer C: To watch the rear of the vehicle clear other vehicles and objects
In a long vehicle the rear wheels cut inside the path of the front wheels, so only the mirrors show whether the rear is clearing curbs, poles and other vehicles.
-
3. Two tires in a dual set have noticeably different diameters. Why is that a problem?
Show answer
Answer C: The larger tire carries more than its share of the load and can be overloaded
The taller tire touches the road first and takes most of the weight, so it runs overloaded and hot while the smaller one does little work.
-
4. 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.
-
5. You can see a crack in a brake drum that runs across more than half the width of the friction surface. What does this mean?
Show answer
Answer C: The drum is defective and must be repaired before the vehicle is driven
Cracks longer than half the width of the friction area mean the drum can break apart under braking heat and must be replaced.
-
6. You are given a ratchet strap with a deep cut along one edge. What should you do?
Show answer
Answer C: Do not use it; a damaged tiedown cannot be relied on to hold its rated load
Cuts, burns, knots and broken stitching weaken a strap far below its marked working load limit, so it must be taken out of service.
-
7. You are hauling a load of steel plate that is well within every weight limit but is stacked five feet high on a flatbed. What is the main concern?
Show answer
Answer A: The center of gravity is high, so the rig will roll more easily in a curve
Legal weight does not make a load safe; height raises the center of gravity and it is height, not weight alone, that decides how readily the vehicle rolls over.
-
8. What blood alcohol content makes driving illegal in Missouri for an adult in a car and for a commercial driver?
Show answer
Answer A: .08 percent in a car and .04 percent in a commercial vehicle
Missouri sets .08 percent for drivers aged 21 and over, .04 percent for commercial vehicle drivers, and .02 percent for drivers under 21.
-
9. What is checked about the clutch and the gearshift during the in-cab inspection?
Show answer
Answer D: That the clutch free play is within the range the manufacturer specifies
Too little or too much clutch free play causes slipping or dragging, either of which can leave the driver unable to select the gear a hill demands.
-
10. What is the risk when too little weight rests on the drive axles?
Show answer
Answer A: Poor traction, so the drive wheels spin easily on wet or slippery surfaces
Traction depends on weight pressing the driving tires onto the road, so a light drive axle spins on wet, snowy or loose surfaces.
-
11. 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.
-
12. During the engine compartment check, which leaks are you looking for?
Show answer
Answer D: Fuel, coolant, engine oil, power steering fluid and battery fluid
Every fluid in the compartment matters, because a fuel leak is a fire risk and a loss of coolant, oil, steering fluid or electrolyte can disable the vehicle.
-
13. 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.
-
14. 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.
-
15. 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.
-
16. 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.
-
17. Where should a trailer be dropped, and what else does the driver do before pulling out from under it?
Show answer
Answer C: On solid level ground, with the trailer wheels chocked if it may roll
A dropped trailer must sit on ground that will carry the landing gear without sinking, and chocks stop it rolling once the tractor and its air supply are gone.
-
18. Which exhaust system condition must be reported as a defect?
Show answer
Answer B: A section repaired by wrapping tape or patching material around the pipe
Exhaust parts may not be patched with wrap or tape, because the repair does not contain the gas or the heat and it fails quickly in service.
-
19. How should speed and gears be handled when approaching a curve?
Show answer
Answer A: Slow to a safe speed and downshift before entering the curve
Braking and shifting are completed before the curve so the vehicle is settled and can pull gently through it without upsetting the load.
-
20. You pick up a trailer that another driver dropped in the yard. What must you do before pulling it?
Show answer
Answer B: Inspect it yourself, because you are responsible for the whole vehicle you drive
Responsibility follows the driver who moves the vehicle, and a trailer that has stood in a yard may have lost air, developed a flat tire or been damaged.
-
21. How can a driver restart the 60 or 70 hour on-duty limit?
Show answer
Answer B: Take 34 or more consecutive hours off duty
A period of 34 or more consecutive hours off duty resets the 60 or 70 hour calculation so the driver can begin a new period.
-
22. A brake light lens is cracked and the lamp still lights. How should that be treated?
Show answer
Answer B: As a defect, because water can enter and the lamp can dim or fail
A cracked lens lets in water and dirt, which corrodes the socket and dulls the lamp, so it is reported before it becomes a dead brake light.
-
23. Which of these is a major cause of skids in heavy vehicles?
Show answer
Answer C: Over-braking, over-steering, over-acceleration or driving too fast for conditions
Skids happen when the tires are asked for more grip than the road can give, which happens through braking, steering or accelerating too hard or simply too much speed.
-
24. 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.
-
25. How many questions are on the Missouri CDL general knowledge written examination?
Show answer
Answer D: 50 questions
Section 14 of the Missouri Commercial Driver License Manual lists 50 questions for the general knowledge examination, and the applicant must score 80 percent on each exam.
-
26. 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.
-
27. A carrier operates commercial vehicles every day of the week. What weekly on-duty limit applies to its drivers?
Show answer
Answer A: 70 hours in 8 consecutive days
The limit is 60 hours in 7 consecutive days for a carrier that does not run every day, and 70 hours in 8 consecutive days for one that does.
-
28. You must leave the vehicle parked on a slight grade. What adds security beyond setting the parking brake?
Show answer
Answer D: Chocking the wheels so the vehicle cannot roll if the brake bleeds off
Chocks hold the vehicle mechanically and are the standard backup whenever a parked vehicle could roll.
-
29. What does a front-end header board on a van or flatbed protect against?
Show answer
Answer A: Cargo moving forward toward the cab in a crash or hard stop
The header board, often called a headache rack, blocks forward movement of the load toward the driver.
-
30. Where on a tire is tread depth measured?
Show answer
Answer C: In a major tread groove, away from any tie bar or wear indicator
Depth is taken in a major groove and away from the raised tie bars and wear indicators, which would give a shallower and misleading reading.
-
31. You miss a gear while double clutching and the transmission is stuck in neutral. What should you do?
Show answer
Answer B: Return to neutral, release the clutch, bring engine speed to match road speed and try again
Forcing the lever damages the gears; matching the engine speed to the road speed lets the gear engage cleanly on the next try.
-
32. Part of your load stands high enough to hide a rear lamp or a reflector. What must be done?
Show answer
Answer B: The load must be moved or extra lamps fitted so the required lights can be seen
Required lamps and reflectors must remain visible; if the cargo blocks them, the load is rearranged or additional lamps are fitted so the vehicle can still be seen.
-
33. 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.
-
34. Why should a long vehicle never swing out to the left before starting a right turn?
Show answer
Answer D: Another driver may read it as a left turn or pass on your right
Swinging left opens a gap on your right that a car will move into, and it also sends a false message about which way you are going.
-
35. A hazard suddenly appears ahead and you must act. Which is usually the faster way to avoid it in a heavy vehicle?
Show answer
Answer B: Steering around it, because you can usually turn faster than you can stop
Stopping distance at speed is very long, so a quick turn out of the way, when there is room, avoids the crash sooner than braking.
-
36. How are the extra gears of a multi-speed rear axle or auxiliary transmission usually controlled?
Show answer
Answer D: With a selector knob or switch on the gearshift lever of the main transmission
A range selector on the shift lever lets the driver choose the extra gear range while shifting the main transmission.
-
37. You are moving an oversized load under a permit that requires a pilot vehicle. What is the pilot vehicle there to do?
Show answer
Answer B: Warn other traffic and check the route ahead for clearances and hazards
Escort or pilot vehicles warn approaching traffic and scout the route for low bridges, narrow spots and other hazards that a wide or long load cannot pass.
-
38. 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.
-
39. What does the gross vehicle weight rating of a vehicle describe?
Show answer
Answer A: The maximum loaded weight of that single vehicle, as specified by the manufacturer
The rating is the manufacturer figure for the loaded weight of one vehicle, so it is a limit fixed in advance rather than a measurement of the load on board today.
-
40. 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.
-
41. Which items belong to the trailer part of the walkaround inspection?
Show answer
Answer D: Landing gear, doors, tires, wheels, lights, reflectors, frame and cargo securement
The trailer has its own running gear, lighting, structure and load, and all of it is the responsibility of the driver pulling it.
-
42. The combined working load limit of the tiedowns on a load must equal at least what share of the cargo weight?
Show answer
Answer C: One half of the cargo weight
Federal securement rules set the aggregate working load limit at no less than half the weight of the article or group of articles being held.
-
43. On a scale, your loaded truck is well under the gross weight limit, but one axle is above the limit for that axle. What does this mean?
Show answer
Answer D: The vehicle is overloaded and the load must be shifted or reduced before you drive on
Each axle and axle group has its own limit and each must be respected; being under the gross limit does not excuse an overloaded axle.
-
44. Where on the road are you most likely to find ice in cold weather?
Show answer
Answer B: On bridges, overpasses and shaded stretches, which freeze before the rest of the road
Bridges and overpasses lose heat from above and below, and shaded areas get no sun, so they ice over first and stay icy longest.
-
45. While double clutching, what goes wrong if you take too long between the two clutch movements?
Show answer
Answer A: Engine speed falls too far and the gear becomes hard or impossible to engage
Double clutching only works while engine speed and road speed still match; a slow shift lets rpm drop away and the gear will not go in.
-
46. How does the working load limit of a tiedown relate to the force that would break it?
Show answer
Answer B: The working load limit is a fraction of the breaking strength and is the figure you use
The working load limit is set well below the point at which the device would fail, and securement is always calculated from the working load limit, never from breaking strength.
-
47. What is a bulkhead in a cargo body used for?
Show answer
Answer D: To divide the space and stop cargo from moving into another part of the body
A bulkhead is a solid partition that separates one part of the load space from another and blocks the cargo from moving past it.
-
48. A 60 foot combination traveling above 40 mph should hold how many seconds of following distance?
Show answer
Answer D: Seven seconds
Six seconds cover the 60 feet of vehicle length, and one extra second is added because the speed is above 40 mph.
-
49. Which clues warn you that a parked car may pull out or open a door?
Show answer
Answer A: Exhaust smoke, turned front wheels, a person in the seat
Signs of life in a parked vehicle, such as a running engine, turned wheels or an occupant, mean it may move or open a door into your path.
-
50. You are unsure whether your vehicle will fit through a narrow gate. What should you do?
Show answer
Answer A: Stop, get out and look, and take another route if the space is not clearly enough
Clearance is never guessed at from the seat; you look at it on foot and go round rather than trying a gap that may be too tight.