District of Columbia DC DMV CDL General Knowledge Practice Test 2
Test 2 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 District of Columbia test.
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
-
1. With water standing on the road, hydroplaning can begin at speeds as low as what?
Show answer
Answer D: 30 mph
When enough water covers the surface, the tires can ride up on it and lose contact at speeds as low as 30 mph.
-
2. 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.
-
3. 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.
-
4. Where are the OVERSIZE LOAD signs normally carried on a vehicle moving under such a permit?
Show answer
Answer A: On the front and the rear of the vehicle
The warning signs face the traffic that meets the load and the traffic that comes up behind it, so they go on the front and the rear.
-
5. 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.
-
6. What must the motor carrier do about a defect listed on a driver vehicle inspection report?
Show answer
Answer D: Repair it, or certify that repair is not needed, before the vehicle is dispatched again
A reported defect must be corrected, or certified as not needing correction, and that certification is what the next driver reads before taking the vehicle.
-
7. You are making a right turn and cannot complete it without swinging into the oncoming lane. An oncoming car is approaching. What should you do?
Show answer
Answer A: Wait and let the oncoming vehicle pass before completing the turn, and do not back up
The oncoming vehicle has the lane; backing up in traffic is dangerous, so hold your position and finish the turn once the way is clear.
-
8. When is a road surface usually most slippery during a rain shower?
Show answer
Answer A: Just after the rain starts, when water mixes with oil and dirt on the surface
The first rain lifts oil and dust into a slick film that has not yet been washed away, so the road is more slippery than it will be later.
-
9. 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.
-
10. You are backing with a helper guiding you and the helper drops out of sight in your mirror. What should you do?
Show answer
Answer B: Stop until you can see the helper again
If you cannot see the helper you cannot receive a signal to stop, so the only safe action is to halt until visual contact is restored.
-
11. Which steering system findings count as defects during the inspection?
Show answer
Answer C: Bent, loose or broken column parts, arms, drag links or tie rods, and missing nuts, bolts or cotter keys
Every joint and fastener between the steering wheel and the tires carries the driver commands, so looseness or a missing retainer can end in a complete loss of steering.
-
12. How long is a DC commercial driver license valid?
Show answer
Answer C: Eight years
DC DMV issues the commercial driver license for a term of eight years, after which it can be renewed.
-
13. 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.
-
14. What actually lowers the amount of alcohol in the bloodstream?
Show answer
Answer B: Time
The liver removes alcohol at a fixed rate, so nothing but the passage of time reduces blood alcohol concentration.
-
15. How should a driver use brakes fitted with an antilock system during an emergency stop?
Show answer
Answer C: Brake as usual and keep enough pressure to stay in control while steering around the hazard
The system only works when the brakes are applied hard enough for it to act, so the driver keeps pressure on and steers while the system prevents lockup.
-
16. 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.
-
17. After starting the engine, how quickly should the oil pressure gauge come up to its normal range?
Show answer
Answer B: Within a few seconds
Oil pressure should build within seconds of starting; if it stays low, the engine is not being lubricated and should be shut down.
-
18. An unblocked article is 8 feet long and weighs 900 pounds. How many tiedowns does the federal rule require?
Show answer
Answer B: Two
Only an article that is 5 feet or shorter and 1,100 pounds or lighter can be held with a single tiedown; anything longer than 5 feet needs at least two whatever it weighs.
-
19. What does DC law allow a school bus driver carrying passengers to do with a mobile telephone?
Show answer
Answer C: Nothing; even hands-free use is prohibited while the bus is moving
DC prohibits school bus drivers carrying passengers from using a mobile telephone or other electronic device, including devices with hands-free accessories, while the vehicle is moving.
-
20. 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.
-
21. May a commercial driver use a hand-held phone while stopped at a red light?
Show answer
Answer B: No, a stop in traffic still counts as driving
Hand-held use is allowed only when the vehicle has been moved to the side of or off the highway and halted where it can safely remain stopped.
-
22. 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.
-
23. 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.
-
24. You are stopped in traffic on a steep upgrade behind another truck. How much space should you leave in front?
Show answer
Answer A: Enough that you can pull away without rolling back into the vehicle behind you
Room ahead lets you get moving smoothly on a grade instead of having to hold the vehicle perfectly still or roll back toward the traffic behind.
-
25. Which of these is a suspension defect you must look for during the walkaround?
Show answer
Answer D: Cracked or broken spring leaves, loose or broken U-bolts, or leaking air suspension bags
Broken springs, failed U-bolts and leaking air bags let the axle shift or the body drop, which can make the vehicle impossible to control.
-
26. A dock crew loads and straps the freight. Who is responsible for the load being legal and secure on the road?
Show answer
Answer D: The driver
Even when someone else loads and secures the freight, the driver must inspect it and remains responsible for it while driving.
-
27. Why is backing toward the driver side preferred?
Show answer
Answer C: You can watch the rear of the vehicle directly through the side window
Backing to the left lets the driver look out the window and see the rear of the vehicle directly instead of relying on a mirror alone.
-
28. 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.
-
29. You are about to back across a quiet street into a driveway. Which of these is good practice before you start to move?
Show answer
Answer B: Turn on the four-way flashers and sound the horn to alert anyone nearby
Warning other road users and pedestrians before a reverse maneuver gives them the chance to stop or move clear before the vehicle starts back.
-
30. 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.
-
31. At what time of day do drowsy driving crashes occur most often?
Show answer
Answer A: Between midnight and 6 a.m.
The body clock makes people sleepiest in the early morning hours, which is when most fatigue-related crashes happen.
-
32. When should a driver select the gear for a long, steep downgrade?
Show answer
Answer B: Before starting down the grade
The low gear has to be chosen before the descent, because a heavy vehicle gaining speed may refuse to shift down at all.
-
33. How much free play in the steering wheel is enough to make a vehicle hard to steer and should be reported?
Show answer
Answer B: More than 10 degrees, roughly 2 inches of movement at the rim of a 20 inch wheel
Excess play means steering input is lost before the wheels respond, and more than about 10 degrees is treated as a defect.
-
34. Under federal rules, what happens to a commercial driver found with any detectable amount of alcohol while operating a commercial vehicle?
Show answer
Answer D: The driver is placed out of service for 24 hours
Any measurable alcohol takes a commercial driver off the road for 24 hours, and a concentration of 0.04 percent or more brings a disqualification.
-
35. 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.
-
36. Why should the radiator cap never be removed while the engine is hot?
Show answer
Answer A: The cooling system is under pressure and scalding coolant can be sprayed out
A hot cooling system holds pressurized coolant above its normal boiling point, so releasing the cap can throw boiling liquid and steam at whoever is holding it.
-
37. How long must a DC applicant wait after failing the CDL road skills test for the second time?
Show answer
Answer B: At least 90 calendar days
A first failure of the DC CDL road skills test carries a three-day wait; a second failure requires at least 90 calendar days.
-
38. Who must sign a driver vehicle inspection report?
Show answer
Answer D: The driver who prepared it
The report is the driver statement about the condition of the vehicle at the end of the day, so the driver signs it.
-
39. What does the commercial driver manual tell you to do with the parking brake when you leave your vehicle?
Show answer
Answer B: Apply the parking brake every time you leave the vehicle
The manual is explicit that the parking brake goes on whenever the driver leaves the vehicle, because once nobody is at the controls it is the only thing holding it.
-
40. 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.
-
41. 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.
-
42. 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.
-
43. A driver snores heavily, stops breathing briefly during the night and is tired all day despite long hours in bed. What should be suspected?
Show answer
Answer B: Sleep apnea
Sleep apnea repeatedly interrupts breathing during sleep, so the driver never gets true rest and stays dangerously drowsy during the day.
-
44. 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.
-
45. Why should a large vehicle be accelerated smoothly and gradually?
Show answer
Answer A: Rough acceleration can damage the drivetrain and, on a combination, the coupling
Jerky throttle inputs put shock loads through the driveline and the coupling, which causes mechanical damage over time.
-
46. During the walkaround you notice one tire on an axle is a radial and the tire next to it is bias-ply. What should you do?
Show answer
Answer B: Treat it as a defect, because radial and bias-ply tires must not be mixed on the same axle
Radial and bias-ply tires flex and grip differently, so mixing them on one axle makes the vehicle handle unpredictably and is not allowed.
-
47. 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.
-
48. You must steer hard around an obstacle at highway speed. What is the correct technique?
Show answer
Answer B: Avoid braking while turning, turn only as far as needed, and countersteer as soon as the obstacle is passed
Braking during a hard steering input can lock the wheels and start a skid, and turning back at once keeps the vehicle from running off the far side of the road.
-
49. At highway speed, looking 12 to 15 seconds ahead means looking about how far down the road?
Show answer
Answer B: About a quarter of a mile
Twelve to fifteen seconds of travel is roughly a quarter of a mile at highway speed, while the same amount of time is about one block in slow city traffic.
-
50. 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.