Delaware DMV CDL General Knowledge Practice Test 6
- Questions50
- Correct to pass40
- Passing score80%
- Minimum age18 years
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1. A driver snores heavily, stops breathing briefly during the night and is tired all day despite long hours in bed. What should be suspected?
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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.
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2. An oncoming vehicle at night has bright headlights that are making it hard to see. What should you do?
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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.
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3. Why should you never shift gears while crossing railroad tracks?
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Answer A: You could miss the gear or stall and be stuck on the tracks
A stalled or coasting vehicle on the tracks has no way to clear quickly, so choose the gear before the crossing and do not shift until you are across.
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4. What happens when too much of the load sits over the steering axle?
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Answer D: The vehicle becomes hard to steer and the axle and its tires can be damaged
Weight beyond the front axle rating makes the steering heavy and can overload the axle and the tires carrying it.
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5. How do you test for leaks in a hydraulic brake system during the pre-trip inspection?
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Answer A: Pump the pedal three times, then hold firm pressure for five seconds and make sure the pedal does not move
If the pedal sinks while you hold pressure, fluid is escaping or air is in the lines, and the vehicle must not be driven until the problem is repaired.
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6. An unblocked crate 4 feet long and weighing 1,500 pounds needs at least how many tiedowns?
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Answer A: Two
A short article that weighs more than 1,100 pounds requires at least two tiedowns even though it is under 5 feet long.
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7. Under federal rules, what is required of a commercial driver who wants to use a mobile phone while driving?
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Answer B: The phone must be hands-free and started with no more than a single button press, and it must not be held
Federal rules ban texting and hand-held phone use while driving a commercial vehicle; reaching for, holding or dialing a phone is a violation.
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8. Experienced commercial drivers scan the road ahead by roughly how much travel time?
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Answer B: About 12 to 15 seconds
Looking 12 to 15 seconds ahead gives a heavy vehicle enough room to slow or change lanes smoothly instead of reacting late.
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9. When speed doubles, what happens to braking distance?
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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.
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10. A 60 foot combination traveling above 40 mph should hold how many seconds of following distance?
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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.
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11. You have stopped and a pedestrian is waiting to cross in front of your truck. Why should you not wave the person across?
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Answer C: Another driver may not stop, and your wave sends the person into danger
You cannot control what drivers in the other lanes will do, so you should not invite a pedestrian into a lane you do not command.
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12. Where is a dunnage bag used and how does it work?
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Answer D: Between pieces of cargo inside a van, where it is inflated to take up the gap
A dunnage bag is placed in the void between loads and inflated so the cargo is wedged and cannot move as the vehicle rolls and brakes.
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13. Two vehicles of exactly the same length make a right turn, one gently and one very tightly. What is the effect on off-tracking?
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Answer A: Turning more sharply increases off-tracking, so the tight turn needs more room
Off-tracking depends on both the length of the vehicle and the sharpness of the turn; a tighter corner brings the rear wheels further inside the path of the front wheels.
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14. How should the headlamps be checked during the pre-trip inspection?
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Answer A: By switching on both low beam and high beam and confirming each one works outside
Both beams are separate circuits, so each is switched on in turn and confirmed from outside the vehicle where the lamps can actually be seen.
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15. Why is a quick lane change particularly risky with a load of hanging meat or of livestock?
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Answer A: The load swings or leans and can keep pushing the trailer after you straighten out
A swinging or leaning load keeps moving after the vehicle has finished the maneuver, so its momentum acts on the trailer at the worst moment.
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16. Which document must be available to show that the annual inspection was carried out?
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Answer C: The inspection report or a copy of it, or a decal displayed on the vehicle
Proof of the periodic inspection travels with the vehicle, either as the report itself or as the decal fixed where an inspector can see it.
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17. When is tire pressure most accurately compared with the recommended figure?
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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.
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18. An oncoming vehicle drifts across the center line into your lane. What is usually the safest move?
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Answer C: Steer to the right, toward the shoulder if necessary
Moving right keeps you away from the drifting vehicle and off the oncoming side; the other driver may swerve back and hit you if you go left.
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19. You are taking a tightly curved highway exit ramp in a long combination. Where should the tractor be placed within the lane?
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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.
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20. What does the working load limit stamped on a chain or strap describe?
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Answer B: The maximum load the device is rated to hold in normal use
The working load limit is the rated safe capacity for everyday use, deliberately set well below the force that would break the device.
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21. Your axle weights are legal, but the tires on that axle are rated below the weight it is carrying. What controls?
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Answer B: The lower figure, so the tires may not be loaded beyond their marked rating
You may never exceed the rating marked on a tire, even when the axle limit would allow more, because an overloaded tire builds heat and can fail.
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22. You pick up a sealed trailer at a shipper. What should you check before leaving the dock?
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Answer B: That the seal number matches the paperwork and that the doors are properly closed
You cannot look at a sealed load, but you can confirm that the seal is intact, that its number matches the documents and that the doors are secure.
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23. Under federal safety rules, what must the driver of a commercial vehicle do before starting a trip?
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Answer A: Be satisfied that the vehicle is in safe operating condition
The driver is responsible for inspecting the vehicle and must be satisfied it is in safe operating condition before the trip begins.
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24. A fire starts in the cargo area of a van trailer. Why should you keep the doors closed until firefighters arrive?
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Answer D: Opening the doors lets in air that feeds the fire
A fire in a closed van is starved of oxygen; opening the doors gives it the air it needs to flare up.
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25. You are loading lengths of large diameter pipe on a flatbed. What is needed besides the tiedowns?
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Answer D: Chocks, wedges or cradles that keep the pipe from rolling
Anything that can roll must be prevented from rolling by chocks, wedges, cradles or a similar device that is itself secured so it cannot come out.
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26. You are driving past a park where children are playing close to the curb. What is the correct assumption?
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Answer A: A child may run into the street without looking
Children act on impulse and do not judge traffic well, so a driver has to expect one to enter the road and slow down in advance.
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27. What color must the clearance and side marker lamps and reflectors at the front of a trailer be?
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Answer A: Amber
Amber marks the front and the forward part of the sides of a vehicle, while red marks the rear, so another driver can tell which way the vehicle is facing.
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28. How do objects appear in a convex mirror compared with a flat mirror?
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Answer B: Smaller and farther away than they really are, while a wider area is shown
A convex mirror shows a wider field but shrinks everything in it, so the driver must remember that vehicles are closer than they look.
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29. Why must you never coast down a hill in neutral or with the clutch pushed in?
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Answer C: You lose the braking effect of the engine and your brakes may overheat and fail
Engine braking is what keeps a heavy vehicle in check on a grade; coasting throws it away and leaves the service brakes to do all the work until they overheat.
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30. You are pulling away from a curb in a 65 foot combination. Besides traffic, what must you watch?
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Answer B: The trailer wheels, which stay close to the curb and can strike it or an object on it
Because of off-tracking, the rear wheels follow a tighter path than the front, so they stay near the curb while the cab is already out in the lane.
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31. What does the gross vehicle weight rating of a vehicle describe?
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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.
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32. A commercial vehicle stops on the shoulder of a one-way or divided highway. Where do the three warning devices go?
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Answer A: At 10 feet, 100 feet, and 200 feet back toward approaching traffic
Traffic arrives from one direction only, so all three devices are set back toward it at 10, 100, and 200 feet, and they must be out within ten minutes.
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33. A strap is a little too long, so a driver ties a knot in it to take up the slack. Is that acceptable?
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Answer C: No, tiedowns must not contain knots
A knot destroys the rated strength of a tiedown, so the rules do not allow knotted securement devices; the excess is taken up by the winch or ratchet instead.
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34. Why should both outside mirrors be checked over and over while backing?
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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.
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35. You normally pull an empty trailer, but today the same tractor is loaded to its legal maximum. What changes about getting under way?
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Answer A: You may need to start in a lower gear, since the load takes more pulling power
The heavier the load, the lower the gear needed to get the vehicle rolling without lugging or stalling the engine.
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36. Before raising the hood to inspect the engine compartment, what should you do?
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Answer B: Shut off the engine, set the parking brake and chock the wheels if needed
The engine compartment is inspected with the engine off and the vehicle secured so nothing can move or turn while your hands are inside.
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37. When a helper guides you while backing, what should be agreed on before you start?
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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.
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38. Why is cargo often covered with a tarp?
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Answer C: To protect people from spilled cargo and to protect the cargo from weather
A cover keeps material from blowing or spilling onto the road and shields the load from rain and sun; it does not replace securement.
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39. Why is braking while in a curve dangerous in a heavy vehicle?
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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.
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40. What is the risk when too little weight rests on the drive axles?
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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.
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41. Total stopping distance is made up of which parts?
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Answer A: Perception distance, reaction distance and braking distance
The vehicle travels while the hazard is recognized, while the driver moves to the pedal, and again while the brakes slow the vehicle.
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42. During the walkaround inspection, where does the driver normally start and how does the check proceed?
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Answer C: At the left front of the vehicle, working around it in a set order that returns to the cab
The walkaround follows the same route every time, starting at the left front and circling the vehicle, so that nothing is skipped when the driver is tired or rushed.
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43. You are moving an oversized load under a permit that requires a pilot vehicle. What is the pilot vehicle there to do?
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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.
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44. What should you do with the previous driver vehicle inspection report before starting your trip?
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Answer B: Review it and confirm that listed defects were certified as repaired or as not needing repair
Reviewing the last report and the carrier certification tells you whether reported defects have been corrected before you take the vehicle out.
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45. The brake pedal goes to the floor in a vehicle with hydraulic brakes. What can you do to build some braking pressure?
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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.
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46. When should a driver select the gear for a long, steep downgrade?
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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.
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47. Federal rules keep recapped and retreaded tires off the front wheels of which vehicle?
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Answer B: Any bus carrying passengers
The federal rule names buses: a bus may not run with regrooved, recapped or retreaded tires on its front wheels, because a steer tire failure with passengers aboard takes away steering control.
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48. You are inspecting the vehicle alone and need to confirm that the stop lights work. Which method is correct?
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Answer A: Have a helper press the brake pedal, or apply the brake in a way that keeps it on while you check from outside
Stop lights are checked from outside the vehicle while the brakes are applied, so a helper or a brake held on is needed.
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49. What does the suspension system weight rating tell the driver?
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Answer A: The maximum weight that the manufacturer says the suspension can carry
Like tires and axles, suspensions have a manufacturer capacity, and loading beyond it can damage springs and air bags.
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50. What is the most common cause of a front-wheel skid, where the vehicle keeps going straight even though you turn the wheel?
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Answer B: Driving too fast for the conditions
A front-wheel skid usually comes from too much speed for the traction available; the only cure is to let the vehicle slow down and stop turning or braking so hard.